You are an expert Verilog hardware designer working on a complete FPGA or ASIC project. You are given the full source code of a Verilog project. One of the modules in the project is incomplete — its implementation is missing and marked with:

// >>> Module Implementation Begin

// <<< Module Implementation End

Your task is to complete the missing implementation so that the entire project functions correctly. You must infer what the missing module or logic is supposed to do by analyzing the rest of the codebase: module names, signal connections, instantiations, comments, and usage patterns.

Follow these rules:

1. Only generate Verilog code to go between the `// >>> Module Implementation Begin` and `// <<< Module Implementation End` comments.
2. Use Verilog-2001 syntax. Ensure the code is synthesizable.
3. Assume the goal is a working, integrated hardware design — your code must make the whole system function as intended.
4. Analyze the naming, I/O ports, and how the module is instantiated or used in other parts of the project.
5. Implement correct behavior based on design context. Do not guess randomly — reason it out.
6. Avoid vendor-specific features unless explicitly required.
7. Do not output comments, explanation, or anything outside the required code region unless explicitly asked.

Your output should contain **only the Verilog code** that fits inside the marked region.

`default_nettype none
//---------------------------------------------
// Top-level module
//---------------------------------------------
module tt_um_space_invaders_game  (
       input  wire [7:0] ui_in,
    output wire [7:0] uo_out,
    input  wire [7:0] uio_in,
    output wire [7:0] uio_out,
    output wire [7:0] uio_oe,
    input  wire       ena,
    input  wire       clk,
    input  wire       rst_n
);

    //----------------------------------------------------
    // 1) VGA Sync + signals
    //----------------------------------------------------
    wire hsync, vsync, video_active;
    wire [9:0] pix_x, pix_y;
    reg  [1:0] R, G, B;

    // Output to VGA: bits => { hsync, B0, G0, R0, vsync, B1, G1, R1 }
    assign uo_out = { hsync, B[0], G[0], R[0],
                      vsync, B[1], G[1], R[1] };

    // Unused I/O
    assign uio_out = 0;
    assign uio_oe  = 0;
    wire _unused_ok = &{ena, ui_in[7:3], uio_in};

    // Minimal VGA generator
    vga_sync_generator sync_gen (
        .clk(clk),
        .reset(~rst_n),
        .hsync(hsync),
        .vsync(vsync),
        .display_on(video_active),
        .hpos(pix_x),
        .vpos(pix_y)
    );

    //----------------------------------------------------
    // 2) Shared horizontal movement for Alien Group
    //----------------------------------------------------
    localparam SMALL_SIZE    = 16;  
    localparam MEDIUM_SIZE   = 16;  
    localparam ALIEN_SPACING = 15;
    localparam NUM_ALIENS    = 8;   
    localparam MIN_LEFT      = 80;
    localparam MAX_RIGHT     = 450;

    // Positions for each row
    localparam [9:0] SMALL_Y    = 150; 
    localparam [9:0] MEDIUM_Y1  = 180; 
    localparam [9:0] MEDIUM_Y2  = 210; 
    localparam [9:0] LARGE_Y1   = 240;  
    localparam [9:0] LARGE_Y2   = 270;  

    reg [9:0] group_x;
    reg       move_dir;    // 1 => move right, 0 => move left
    reg [9:0] prev_vpos;

    always @(posedge clk) begin
        if (~rst_n) begin
            group_x   <= 100;
            move_dir  <= 1;   
            prev_vpos <= 0;
        end else begin
            // Once per frame
            prev_vpos <= pix_y;
            if (pix_y == 0 && prev_vpos != 0) begin
                // Move entire group horizontally
                if (move_dir) group_x <= group_x + 2;
                else          group_x <= group_x - 2;

                // Bounce at boundaries
                if (group_x <= MIN_LEFT && !move_dir)
                    move_dir <= 1;
                else if ((group_x + (SMALL_SIZE+ALIEN_SPACING)*(NUM_ALIENS-1)
                          + SMALL_SIZE) >= MAX_RIGHT && move_dir)
                    move_dir <= 0;
            end
        end
    end

    //----------------------------------------------------
    // 3) Data Structures for Collision Detection
    //----------------------------------------------------
    
    localparam NUM_ALIENS_PER_ROW = 8;
    localparam NUM_ROWS_ALIENS    = 5;
    localparam NUM_BARRIERS = 4;
    reg aliens_alive [0:NUM_ROWS_ALIENS-1][0:NUM_ALIENS_PER_ROW-1];
    reg [2:0] barrier_health [0:NUM_BARRIERS-1]; 
    reg [1:0] shooter_lives; 


    //----------------------------------------------------
    // 4) Small Aliens (16×16) in one row
    //----------------------------------------------------
    wire s1_on, s2_on, s3_on, s4_on;
    wire s5_on, s6_on, s7_on, s8_on;

    wire [9:0] s1_x = group_x;
    wire [9:0] s2_x = group_x + (SMALL_SIZE + ALIEN_SPACING)*1;
    wire [9:0] s3_x = group_x + (SMALL_SIZE + ALIEN_SPACING)*2;
    wire [9:0] s4_x = group_x + (SMALL_SIZE + ALIEN_SPACING)*3;
    wire [9:0] s5_x = group_x + (SMALL_SIZE + ALIEN_SPACING)*4;
    wire [9:0] s6_x = group_x + (SMALL_SIZE + ALIEN_SPACING)*5;
    wire [9:0] s7_x = group_x + (SMALL_SIZE + ALIEN_SPACING)*6;
    wire [9:0] s8_x = group_x + (SMALL_SIZE + ALIEN_SPACING)*7;

    draw_small_alien smA1(.pix_x(pix_x), .pix_y(pix_y),
                          .alien_left_x(s1_x), .alien_top_y(SMALL_Y),
                          .pixel_on(s1_on));
    draw_small_alien smA2(.pix_x(pix_x), .pix_y(pix_y),
                          .alien_left_x(s2_x), .alien_top_y(SMALL_Y),
                          .pixel_on(s2_on));
    draw_small_alien smA3(.pix_x(pix_x), .pix_y(pix_y),
                          .alien_left_x(s3_x), .alien_top_y(SMALL_Y),
                          .pixel_on(s3_on));
    draw_small_alien smA4(.pix_x(pix_x), .pix_y(pix_y),
                          .alien_left_x(s4_x), .alien_top_y(SMALL_Y),
                          .pixel_on(s4_on));
    draw_small_alien smA5(.pix_x(pix_x), .pix_y(pix_y),
                          .alien_left_x(s5_x), .alien_top_y(SMALL_Y),
                          .pixel_on(s5_on));
    draw_small_alien smA6(.pix_x(pix_x), .pix_y(pix_y),
                          .alien_left_x(s6_x), .alien_top_y(SMALL_Y),
                          .pixel_on(s6_on));
    draw_small_alien smA7(.pix_x(pix_x), .pix_y(pix_y),
                          .alien_left_x(s7_x), .alien_top_y(SMALL_Y),
                          .pixel_on(s7_on));
    draw_small_alien smA8(.pix_x(pix_x), .pix_y(pix_y),
                          .alien_left_x(s8_x), .alien_top_y(SMALL_Y),
                          .pixel_on(s8_on));

    //----------------------------------------------------
    // 5) Medium Aliens (16×16) in 2 rows
    //----------------------------------------------------
    wire mA1_on, mA2_on, mA3_on, mA4_on;
    wire mA5_on, mA6_on, mA7_on, mA8_on;

    wire [9:0] mA1_x = group_x;
    wire [9:0] mA2_x = group_x + (MEDIUM_SIZE + ALIEN_SPACING)*1;
    wire [9:0] mA3_x = group_x + (MEDIUM_SIZE + ALIEN_SPACING)*2;
    wire [9:0] mA4_x = group_x + (MEDIUM_SIZE + ALIEN_SPACING)*3;
    wire [9:0] mA5_x = group_x + (MEDIUM_SIZE + ALIEN_SPACING)*4;
    wire [9:0] mA6_x = group_x + (MEDIUM_SIZE + ALIEN_SPACING)*5;
    wire [9:0] mA7_x = group_x + (MEDIUM_SIZE + ALIEN_SPACING)*6;
    wire [9:0] mA8_x = group_x + (MEDIUM_SIZE + ALIEN_SPACING)*7;

    draw_medium_alien mdA1(.pix_x(pix_x), .pix_y(pix_y),
                           .alien_left_x(mA1_x), .alien_top_y(MEDIUM_Y1),
                           .pixel_on(mA1_on));
    draw_medium_alien mdA2(.pix_x(pix_x), .pix_y(pix_y),
                           .alien_left_x(mA2_x), .alien_top_y(MEDIUM_Y1),
                           .pixel_on(mA2_on));
    draw_medium_alien mdA3(.pix_x(pix_x), .pix_y(pix_y),
                           .alien_left_x(mA3_x), .alien_top_y(MEDIUM_Y1),
                           .pixel_on(mA3_on));
    draw_medium_alien mdA4(.pix_x(pix_x), .pix_y(pix_y),
                           .alien_left_x(mA4_x), .alien_top_y(MEDIUM_Y1),
                           .pixel_on(mA4_on));
    draw_medium_alien mdA5(.pix_x(pix_x), .pix_y(pix_y),
                           .alien_left_x(mA5_x), .alien_top_y(MEDIUM_Y1),
                           .pixel_on(mA5_on));
    draw_medium_alien mdA6(.pix_x(pix_x), .pix_y(pix_y),
                           .alien_left_x(mA6_x), .alien_top_y(MEDIUM_Y1),
                           .pixel_on(mA6_on));
    draw_medium_alien mdA7(.pix_x(pix_x), .pix_y(pix_y),
                           .alien_left_x(mA7_x), .alien_top_y(MEDIUM_Y1),
                           .pixel_on(mA7_on));
    draw_medium_alien mdA8(.pix_x(pix_x), .pix_y(pix_y),
                           .alien_left_x(mA8_x), .alien_top_y(MEDIUM_Y1),
                           .pixel_on(mA8_on));

    wire mB1_on, mB2_on, mB3_on, mB4_on;
    wire mB5_on, mB6_on, mB7_on, mB8_on;

    wire [9:0] mB1_x = group_x;
    wire [9:0] mB2_x = group_x + (MEDIUM_SIZE + ALIEN_SPACING)*1;
    wire [9:0] mB3_x = group_x + (MEDIUM_SIZE + ALIEN_SPACING)*2;
    wire [9:0] mB4_x = group_x + (MEDIUM_SIZE + ALIEN_SPACING)*3;
    wire [9:0] mB5_x = group_x + (MEDIUM_SIZE + ALIEN_SPACING)*4;
    wire [9:0] mB6_x = group_x + (MEDIUM_SIZE + ALIEN_SPACING)*5;
    wire [9:0] mB7_x = group_x + (MEDIUM_SIZE + ALIEN_SPACING)*6;
    wire [9:0] mB8_x = group_x + (MEDIUM_SIZE + ALIEN_SPACING)*7;

    draw_medium_alien mdB1(.pix_x(pix_x), .pix_y(pix_y),
                           .alien_left_x(mB1_x), .alien_top_y(MEDIUM_Y2),
                           .pixel_on(mB1_on));
    draw_medium_alien mdB2(.pix_x(pix_x), .pix_y(pix_y),
                           .alien_left_x(mB2_x), .alien_top_y(MEDIUM_Y2),
                           .pixel_on(mB2_on));
    draw_medium_alien mdB3(.pix_x(pix_x), .pix_y(pix_y),
                           .alien_left_x(mB3_x), .alien_top_y(MEDIUM_Y2),
                           .pixel_on(mB3_on));
    draw_medium_alien mdB4(.pix_x(pix_x), .pix_y(pix_y),
                           .alien_left_x(mB4_x), .alien_top_y(MEDIUM_Y2),
                           .pixel_on(mB4_on));
    draw_medium_alien mdB5(.pix_x(pix_x), .pix_y(pix_y),
                           .alien_left_x(mB5_x), .alien_top_y(MEDIUM_Y2),
                           .pixel_on(mB5_on));
    draw_medium_alien mdB6(.pix_x(pix_x), .pix_y(pix_y),
                           .alien_left_x(mB6_x), .alien_top_y(MEDIUM_Y2),
                           .pixel_on(mB6_on));
    draw_medium_alien mdB7(.pix_x(pix_x), .pix_y(pix_y),
                           .alien_left_x(mB7_x), .alien_top_y(MEDIUM_Y2),
                           .pixel_on(mB7_on));
    draw_medium_alien mdB8(.pix_x(pix_x), .pix_y(pix_y),
                           .alien_left_x(mB8_x), .alien_top_y(MEDIUM_Y2),
                           .pixel_on(mB8_on));

    //----------------------------------------------------
    // 6) Large Aliens (16×16) in 2 rows
    //----------------------------------------------------
    wire lA1_on, lA2_on, lA3_on, lA4_on;
    wire lA5_on, lA6_on, lA7_on, lA8_on;

    wire [9:0] lA1_x = group_x;
    wire [9:0] lA2_x = group_x + (MEDIUM_SIZE + ALIEN_SPACING)*1;
    wire [9:0] lA3_x = group_x + (MEDIUM_SIZE + ALIEN_SPACING)*2;
    wire [9:0] lA4_x = group_x + (MEDIUM_SIZE + ALIEN_SPACING)*3;
    wire [9:0] lA5_x = group_x + (MEDIUM_SIZE + ALIEN_SPACING)*4;
    wire [9:0] lA6_x = group_x + (MEDIUM_SIZE + ALIEN_SPACING)*5;
    wire [9:0] lA7_x = group_x + (MEDIUM_SIZE + ALIEN_SPACING)*6;
    wire [9:0] lA8_x = group_x + (MEDIUM_SIZE + ALIEN_SPACING)*7;

    draw_alien3 lgA1(.pix_x(pix_x), .pix_y(pix_y),
                     .alien_left_x(lA1_x), .alien_top_y(LARGE_Y1),
                     .pixel_on(lA1_on));
    draw_alien3 lgA2(.pix_x(pix_x), .pix_y(pix_y),
                     .alien_left_x(lA2_x), .alien_top_y(LARGE_Y1),
                     .pixel_on(lA2_on));
    draw_alien3 lgA3(.pix_x(pix_x), .pix_y(pix_y),
                     .alien_left_x(lA3_x), .alien_top_y(LARGE_Y1),
                     .pixel_on(lA3_on));
    draw_alien3 lgA4(.pix_x(pix_x), .pix_y(pix_y),
                     .alien_left_x(lA4_x), .alien_top_y(LARGE_Y1),
                     .pixel_on(lA4_on));
    draw_alien3 lgA5(.pix_x(pix_x), .pix_y(pix_y),
                     .alien_left_x(lA5_x), .alien_top_y(LARGE_Y1),
                     .pixel_on(lA5_on));
    draw_alien3 lgA6(.pix_x(pix_x), .pix_y(pix_y),
                     .alien_left_x(lA6_x), .alien_top_y(LARGE_Y1),
                     .pixel_on(lA6_on));
    draw_alien3 lgA7(.pix_x(pix_x), .pix_y(pix_y),
                     .alien_left_x(lA7_x), .alien_top_y(LARGE_Y1),
                     .pixel_on(lA7_on));
    draw_alien3 lgA8(.pix_x(pix_x), .pix_y(pix_y),
                     .alien_left_x(lA8_x), .alien_top_y(LARGE_Y1),
                     .pixel_on(lA8_on));

    wire lB1_on, lB2_on, lB3_on, lB4_on;
    wire lB5_on, lB6_on, lB7_on, lB8_on;

    wire [9:0] lB1_x = group_x;
    wire [9:0] lB2_x = group_x + (MEDIUM_SIZE + ALIEN_SPACING)*1;
    wire [9:0] lB3_x = group_x + (MEDIUM_SIZE + ALIEN_SPACING)*2;
    wire [9:0] lB4_x = group_x + (MEDIUM_SIZE + ALIEN_SPACING)*3;
    wire [9:0] lB5_x = group_x + (MEDIUM_SIZE + ALIEN_SPACING)*4;
    wire [9:0] lB6_x = group_x + (MEDIUM_SIZE + ALIEN_SPACING)*5;
    wire [9:0] lB7_x = group_x + (MEDIUM_SIZE + ALIEN_SPACING)*6;
    wire [9:0] lB8_x = group_x + (MEDIUM_SIZE + ALIEN_SPACING)*7;

    draw_alien3 lgB1(.pix_x(pix_x), .pix_y(pix_y),
                     .alien_left_x(lB1_x), .alien_top_y(LARGE_Y2),
                     .pixel_on(lB1_on));
    draw_alien3 lgB2(.pix_x(pix_x), .pix_y(pix_y),
                     .alien_left_x(lB2_x), .alien_top_y(LARGE_Y2),
                     .pixel_on(lB2_on));
    draw_alien3 lgB3(.pix_x(pix_x), .pix_y(pix_y),
                     .alien_left_x(lB3_x), .alien_top_y(LARGE_Y2),
                     .pixel_on(lB3_on));
    draw_alien3 lgB4(.pix_x(pix_x), .pix_y(pix_y),
                     .alien_left_x(lB4_x), .alien_top_y(LARGE_Y2),
                     .pixel_on(lB4_on));
    draw_alien3 lgB5(.pix_x(pix_x), .pix_y(pix_y),
                     .alien_left_x(lB5_x), .alien_top_y(LARGE_Y2),
                     .pixel_on(lB5_on));
    draw_alien3 lgB6(.pix_x(pix_x), .pix_y(pix_y),
                     .alien_left_x(lB6_x), .alien_top_y(LARGE_Y2),
                     .pixel_on(lB6_on));
    draw_alien3 lgB7(.pix_x(pix_x), .pix_y(pix_y),
                     .alien_left_x(lB7_x), .alien_top_y(LARGE_Y2),
                     .pixel_on(lB7_on));
    draw_alien3 lgB8(.pix_x(pix_x), .pix_y(pix_y),
                     .alien_left_x(lB8_x), .alien_top_y(LARGE_Y2),
                     .pixel_on(lB8_on));

    //----------------------------------------------------
    // 7) Combine signals for small, medium, large aliens
    //----------------------------------------------------
    wire any_small_on =
        (s1_on && aliens_alive[0][0] || 
         s2_on && aliens_alive[0][1] || 
         s3_on && aliens_alive[0][2] || 
         s4_on && aliens_alive[0][3] ||
         s5_on && aliens_alive[0][4] || 
         s6_on && aliens_alive[0][5] || 
         s7_on && aliens_alive[0][6] || 
         s8_on && aliens_alive[0][7]);

    wire any_medium_on =
        (mA1_on && aliens_alive[1][0] || 
         mA2_on && aliens_alive[1][1] || 
         mA3_on && aliens_alive[1][2] || 
         mA4_on && aliens_alive[1][3] ||
         mA5_on && aliens_alive[1][4] || 
         mA6_on && aliens_alive[1][5] || 
         mA7_on && aliens_alive[1][6] || 
         mA8_on && aliens_alive[1][7] ||
         mB1_on && aliens_alive[2][0] || 
         mB2_on && aliens_alive[2][1] || 
         mB3_on && aliens_alive[2][2] || 
         mB4_on && aliens_alive[2][3] ||
         mB5_on && aliens_alive[2][4] || 
         mB6_on && aliens_alive[2][5] || 
         mB7_on && aliens_alive[2][6] || 
         mB8_on && aliens_alive[2][7]);

    wire any_large_on =
        (lA1_on && aliens_alive[3][0] || 
         lA2_on && aliens_alive[3][1] || 
         lA3_on && aliens_alive[3][2] || 
         lA4_on && aliens_alive[3][3] ||
         lA5_on && aliens_alive[3][4] || 
         lA6_on && aliens_alive[3][5] || 
         lA7_on && aliens_alive[3][6] || 
         lA8_on && aliens_alive[3][7] ||
         lB1_on && aliens_alive[4][0] || 
         lB2_on && aliens_alive[4][1] || 
         lB3_on && aliens_alive[4][2] || 
         lB4_on && aliens_alive[4][3] ||
         lB5_on && aliens_alive[4][4] || 
         lB6_on && aliens_alive[4][5] || 
         lB7_on && aliens_alive[4][6] || 
         lB8_on && aliens_alive[4][7]);


  //-----------------------------------------


  localparam TROPHY_X = 100; // 12 pixels padding
  localparam TROPHY_Y = 80;                // Align Y position with scoreboard

  localparam HEART_X =  398;  // Position of the heart to the left of the score
  localparam HEART_Y = 86;  

  wire pixel_on_heart;
  draw_heart draw_heart_inst (
      .pix_x(pix_x),
      .pix_y(pix_y),
      .heart_left_x(HEART_X),
      .heart_top_y(HEART_Y),
      .pixel_on(pixel_on_heart)
  );


  // Instantiate Trophy Drawing Module
  wire pixel_on_trophy;
  draw_trophy draw_trophy_inst (
      .pix_x(pix_x),
      .pix_y(pix_y),
      .trophy_left_x(TROPHY_X),
      .trophy_top_y(TROPHY_Y),
      .pixel_on(pixel_on_trophy)
  );


  //wire final_pixel_on;
  //assign final_pixel_on = pixel_on_heart | pixel_on_trophy;






    //----------------------------------------------------
    // 8) Shooter Movement Direction
    //----------------------------------------------------
    localparam [1:0] DIR_IDLE  = 2'b00,
                     DIR_LEFT  = 2'b01,
                     DIR_RIGHT = 2'b10;

    reg [1:0] movement_dir;
    reg prev_button0, prev_button1;

    always @(posedge clk) begin
      if (~rst_n) begin
        prev_button0  <= 0;
        prev_button1  <= 0;
        movement_dir  <= DIR_IDLE;
      end else begin
        // Capture previous button states for edge-detection
        prev_button0 <= ui_in[0];
        prev_button1 <= ui_in[1];

        // Rising edge on button0 => move right
        if (ui_in[0] && !prev_button0) begin
          movement_dir <= DIR_RIGHT;
        end
        // Rising edge on button1 => move left
        else if (ui_in[1] && !prev_button1) begin
          movement_dir <= DIR_LEFT;
        end
        // If both buttons are released => idle
        else if (!ui_in[0] && !ui_in[1]) begin
          movement_dir <= DIR_IDLE;
        end
      end
    end

    //----------------------------------------------------
    // 9) Shooter Position
    //----------------------------------------------------
    localparam SHOOTER_Y     = 360;  


    reg [9:0] shooter_x;
    reg [9:0] prev_vpos_shooter;

    always @(posedge clk) begin
        if (~rst_n) begin
            shooter_x <= 255;
            prev_vpos_shooter <= 0;
        end 
        else if (game_over) begin
            shooter_x <= 255;
            prev_vpos_shooter <= 0;
        end
        else if (game_won) begin
            shooter_x <= 255;
            prev_vpos_shooter <= 0;
        end
        else begin
            // Update once per frame
            prev_vpos_shooter <= pix_y;
            if (pix_y == 0 && prev_vpos_shooter != 0) begin
                case (movement_dir)
                  DIR_LEFT:  if (shooter_x >= 20) shooter_x <= shooter_x - 10;
                  DIR_RIGHT: if (shooter_x <= 500) shooter_x <= shooter_x + 10;
                  default:   /* idle */ ;
                endcase
            end
        end
    end

    //----------------------------------------------------
    // 10) Draw the Shooter
    //----------------------------------------------------
    wire shooter_on;
    draw_shooter myShooter (
        .pix_x(pix_x),
        .pix_y(pix_y),
        .shooter_left_x(shooter_x),
        .shooter_top_y(SHOOTER_Y),
        .pixel_on(shooter_on)
    );

    //----------------------------------------------------
    // 11) Barriers (32×16 now)
    //----------------------------------------------------
    wire b1_on, b2_on, b3_on, b4_on;
    localparam BARRIER_Y = 320; 

    localparam [9:0] b1_xpos = 100;
    localparam [9:0] b2_xpos = 200;
    localparam [9:0] b3_xpos = 300;
    localparam [9:0] b4_xpos = 400;

    draw_barrier barrier1(.pix_x(pix_x), .pix_y(pix_y),
                          .bar_left_x(b1_xpos), .bar_top_y(BARRIER_Y),
                          .pixel_on(b1_on));
    draw_barrier barrier2(.pix_x(pix_x), .pix_y(pix_y),
                          .bar_left_x(b2_xpos), .bar_top_y(BARRIER_Y),
                          .pixel_on(b2_on));
    draw_barrier barrier3(.pix_x(pix_x), .pix_y(pix_y),
                          .bar_left_x(b3_xpos), .bar_top_y(BARRIER_Y),
                          .pixel_on(b3_on));
    draw_barrier barrier4(.pix_x(pix_x), .pix_y(pix_y),
                          .bar_left_x(b4_xpos), .bar_top_y(BARRIER_Y),
                          .pixel_on(b4_on));

    // Only draw barriers with health > 0
    wire barrier1_visible = (barrier_health[0] > 0) && b1_on;
    wire barrier2_visible = (barrier_health[1] > 0) && b2_on;
    wire barrier3_visible = (barrier_health[2] > 0) && b3_on;
    wire barrier4_visible = (barrier_health[3] > 0) && b4_on;

    wire any_barrier_on = (barrier1_visible || barrier2_visible || barrier3_visible || barrier4_visible);

    //----------------------------------------------------
    //  Multiple Player Bullets + Alien Bullet
    //----------------------------------------------------


    reg pb_active;  
    reg [9:0] pb_x;
    reg [9:0] pb_y;

    // For detecting rising edge of ui_in[2].
    reg prev_button2;
    reg abullet_active;
    reg [9:0]  abullet_x, abullet_y;

    // Minimal LFSR for randomness
    reg [7:0] lfsr;
    wire lfsr_feedback = lfsr[7] ^ lfsr[5] ^ lfsr[4] ^ lfsr[3];


    // Declare new signals to avoid naming conflicts
    reg [2:0] selectedRowRand;
    reg [2:0] colRand;

    // Calculate Row Y Position
    wire [9:0] rowY_0 = SMALL_Y   + 8;
    wire [9:0] rowY_1 = MEDIUM_Y1 + 8;
    wire [9:0] rowY_2 = MEDIUM_Y2 + 8;
    wire [9:0] rowY_3 = LARGE_Y1  + 8;
    wire [9:0] rowY_4 = LARGE_Y2  + 8;
    localparam SHOOTER_WIDTH  = 16; // Adjust as per your shooter design
    localparam SHOOTER_HEIGHT = 16;

    // Barrier Bounding Box Parameters
    localparam BARRIER_WIDTH  = 32;
    localparam BARRIER_HEIGHT = 16;
    reg [9:0] score;
    reg game_over;
    reg game_won;


    
    // We move them once per frame (like your old code).
    always @(posedge clk) begin
      if (~rst_n) begin
        pb_active <= 0;
        pb_x <= 0;  pb_y <= 0;
        
        prev_button2 <= 0;
	      lfsr <= 8'hA5;
        abullet_active <= 0;
        abullet_x <= 0;
        abullet_y <= 0;
        selectedRowRand <= 0;
        colRand <= 0;
        shooter_lives <= 3;
        // Initialize Aliens as alive
        aliens_alive[0][0] <= 1'b1;
        aliens_alive[0][1] <= 1'b1;
        aliens_alive[0][2] <= 1'b1;
        aliens_alive[0][3] <= 1'b1;
        aliens_alive[0][4] <= 1'b1;
        aliens_alive[0][5] <= 1'b1;
        aliens_alive[0][6] <= 1'b1;
        aliens_alive[0][7] <= 1'b1;
        
        aliens_alive[1][0] <= 1'b1;
        aliens_alive[1][1] <= 1'b1;
        aliens_alive[1][2] <= 1'b1;
        aliens_alive[1][3] <= 1'b1;
        aliens_alive[1][4] <= 1'b1;
        aliens_alive[1][5] <= 1'b1;
        aliens_alive[1][6] <= 1'b1;
        aliens_alive[1][7] <= 1'b1;
        
        aliens_alive[2][0] <= 1'b1;
        aliens_alive[2][1] <= 1'b1;
        aliens_alive[2][2] <= 1'b1;
        aliens_alive[2][3] <= 1'b1;
        aliens_alive[2][4] <= 1'b1;
        aliens_alive[2][5] <= 1'b1;
        aliens_alive[2][6] <= 1'b1;
        aliens_alive[2][7] <= 1'b1;
        
        aliens_alive[3][0] <= 1'b1;
        aliens_alive[3][1] <= 1'b1;
        aliens_alive[3][2] <= 1'b1;
        aliens_alive[3][3] <= 1'b1;
        aliens_alive[3][4] <= 1'b1;
        aliens_alive[3][5] <= 1'b1;
        aliens_alive[3][6] <= 1'b1;
        aliens_alive[3][7] <= 1'b1;
        
        aliens_alive[4][0] <= 1'b1;
        aliens_alive[4][1] <= 1'b1;
        aliens_alive[4][2] <= 1'b1;
        aliens_alive[4][3] <= 1'b1;
        aliens_alive[4][4] <= 1'b1;
        aliens_alive[4][5] <= 1'b1;
        aliens_alive[4][6] <= 1'b1;
        aliens_alive[4][7] <= 1'b1;

        // Initialize Barriers Health to 5
        barrier_health[0] <= 3'd5;
        barrier_health[1] <= 3'd5;
        barrier_health[2] <= 3'd5;
        barrier_health[3] <= 3'd5;

      end 
       else if (game_won) begin
        game_won <= 0;
        pb_active <= 0;
        pb_x <= 0;  pb_y <= 0;
        
        prev_button2 <= 0;
	      lfsr <= 8'hA5;
        abullet_active <= 0;
        abullet_x <= 0;
        abullet_y <= 0;
        selectedRowRand <= 0;
        colRand <= 0;
        score <= 0;
        shooter_lives <= 3;
        aliens_alive[0][0] <= 1'b1;
        aliens_alive[0][1] <= 1'b1;
        aliens_alive[0][2] <= 1'b1;
        aliens_alive[0][3] <= 1'b1;
        aliens_alive[0][4] <= 1'b1;
        aliens_alive[0][5] <= 1'b1;
        aliens_alive[0][6] <= 1'b1;
        aliens_alive[0][7] <= 1'b1;
        
        aliens_alive[1][0] <= 1'b1;
        aliens_alive[1][1] <= 1'b1;
        aliens_alive[1][2] <= 1'b1;
        aliens_alive[1][3] <= 1'b1;
        aliens_alive[1][4] <= 1'b1;
        aliens_alive[1][5] <= 1'b1;
        aliens_alive[1][6] <= 1'b1;
        aliens_alive[1][7] <= 1'b1;
        
        aliens_alive[2][0] <= 1'b1;
        aliens_alive[2][1] <= 1'b1;
        aliens_alive[2][2] <= 1'b1;
        aliens_alive[2][3] <= 1'b1;
        aliens_alive[2][4] <= 1'b1;
        aliens_alive[2][5] <= 1'b1;
        aliens_alive[2][6] <= 1'b1;
        aliens_alive[2][7] <= 1'b1;
        
        aliens_alive[3][0] <= 1'b1;
        aliens_alive[3][1] <= 1'b1;
        aliens_alive[3][2] <= 1'b1;
        aliens_alive[3][3] <= 1'b1;
        aliens_alive[3][4] <= 1'b1;
        aliens_alive[3][5] <= 1'b1;
        aliens_alive[3][6] <= 1'b1;
        aliens_alive[3][7] <= 1'b1;
        
        aliens_alive[4][0] <= 1'b1;
        aliens_alive[4][1] <= 1'b1;
        aliens_alive[4][2] <= 1'b1;
        aliens_alive[4][3] <= 1'b1;
        aliens_alive[4][4] <= 1'b1;
        aliens_alive[4][5] <= 1'b1;
        aliens_alive[4][6] <= 1'b1;
        aliens_alive[4][7] <= 1'b1;

        // Initialize Barriers Health to 5
        barrier_health[0] <= 3'd5;
        barrier_health[1] <= 3'd5;
        barrier_health[2] <= 3'd5;
        barrier_health[3] <= 3'd5;
    end
    else if (game_over) begin
        game_over <= 0;
        pb_active <= 0;
        pb_x <= 0;  pb_y <= 0;
        prev_button2 <= 0;
	      lfsr <= 8'hA5;
        abullet_active <= 0;
        abullet_x <= 0;
        abullet_y <= 0;
        selectedRowRand <= 0;
        colRand <= 0;
        score <= 0;
        shooter_lives <= 3;
        aliens_alive[0][0] <= 1'b1;
        aliens_alive[0][1] <= 1'b1;
        aliens_alive[0][2] <= 1'b1;
        aliens_alive[0][3] <= 1'b1;
        aliens_alive[0][4] <= 1'b1;
        aliens_alive[0][5] <= 1'b1;
        aliens_alive[0][6] <= 1'b1;
        aliens_alive[0][7] <= 1'b1;
        
        aliens_alive[1][0] <= 1'b1;
        aliens_alive[1][1] <= 1'b1;
        aliens_alive[1][2] <= 1'b1;
        aliens_alive[1][3] <= 1'b1;
        aliens_alive[1][4] <= 1'b1;
        aliens_alive[1][5] <= 1'b1;
        aliens_alive[1][6] <= 1'b1;
        aliens_alive[1][7] <= 1'b1;
        
        aliens_alive[2][0] <= 1'b1;
        aliens_alive[2][1] <= 1'b1;
        aliens_alive[2][2] <= 1'b1;
        aliens_alive[2][3] <= 1'b1;
        aliens_alive[2][4] <= 1'b1;
        aliens_alive[2][5] <= 1'b1;
        aliens_alive[2][6] <= 1'b1;
        aliens_alive[2][7] <= 1'b1;
        
        aliens_alive[3][0] <= 1'b1;
        aliens_alive[3][1] <= 1'b1;
        aliens_alive[3][2] <= 1'b1;
        aliens_alive[3][3] <= 1'b1;
        aliens_alive[3][4] <= 1'b1;
        aliens_alive[3][5] <= 1'b1;
        aliens_alive[3][6] <= 1'b1;
        aliens_alive[3][7] <= 1'b1;
        
        aliens_alive[4][0] <= 1'b1;
        aliens_alive[4][1] <= 1'b1;
        aliens_alive[4][2] <= 1'b1;
        aliens_alive[4][3] <= 1'b1;
        aliens_alive[4][4] <= 1'b1;
        aliens_alive[4][5] <= 1'b1;
        aliens_alive[4][6] <= 1'b1;
        aliens_alive[4][7] <= 1'b1;

        // Initialize Barriers Health to 5
        barrier_health[0] <= 3'd5;
        barrier_health[1] <= 3'd5;
        barrier_health[2] <= 3'd5;
        barrier_health[3] <= 3'd5;
    end
      else begin
        // Detect rising edge of button #2 each clock:
        if (!prev_button2 && ui_in[2]) begin
          // Attempt to spawn bullet in an empty slot:
          if (!pb_active) begin
            pb_active <= 1;
            pb_x <= shooter_x + 6;
            pb_y <= SHOOTER_Y - 25;
          end 
          // else: no free slot => ignore
        end
        prev_button2 <= ui_in[2];

        // Once per frame: move active bullets up
        if (pix_y == 0 && prev_vpos != 0) begin
		      lfsr <= {lfsr[6:0], lfsr_feedback};
          // Bullet 
          if (pb_active) begin
              if (pb_y > 130)
                  pb_y <= pb_y - 25;
              else
                  pb_active <= 0; // vanish
          end
          
          // Alien Bullet Movement
          if (abullet_active) begin
              if (abullet_y < 390)
                  abullet_y <= abullet_y + 10; 
              else 
                 abullet_active <= 0;

              if (
                        abullet_x + BULLET_W > shooter_x &&
                        abullet_x < shooter_x + SHOOTER_WIDTH &&
                        abullet_y + BULLET_H > SHOOTER_Y &&
                        abullet_y < SHOOTER_Y + SHOOTER_HEIGHT
                    ) begin
                        
                        abullet_active <= 0; 
						if (shooter_lives > 0) begin
						   shooter_lives <= shooter_lives - 1;
						end
                    end
              if (barrier_health[0] > 0 &&
                        abullet_x + BULLET_W > b1_xpos &&
                        abullet_x < b1_xpos + BARRIER_WIDTH &&
                        abullet_y + BULLET_H > BARRIER_Y &&
                        abullet_y < BARRIER_Y + BARRIER_HEIGHT) begin
                            barrier_health[0] <= barrier_health[0] - 1;
                            abullet_active <= 0;
                    end

                    // Barrier 1
              if (barrier_health[1] > 0 &&
                        abullet_x + BULLET_W > b2_xpos &&
                        abullet_x < b2_xpos + BARRIER_WIDTH &&
                        abullet_y + BULLET_H > BARRIER_Y &&
                        abullet_y < BARRIER_Y + BARRIER_HEIGHT) begin
                            barrier_health[1] <= barrier_health[1] - 1;
                            abullet_active <= 0;
                    end

                    // Barrier 2
              if (barrier_health[2] > 0 &&
                        abullet_x + BULLET_W > b3_xpos &&
                        abullet_x < b3_xpos + BARRIER_WIDTH &&
                        abullet_y + BULLET_H > BARRIER_Y &&
                        abullet_y < BARRIER_Y + BARRIER_HEIGHT) begin
                            barrier_health[2] <= barrier_health[2] - 1;
                            abullet_active <= 0;
                    end

                    // Barrier 3
              if (barrier_health[3] > 0 &&
                        abullet_x + BULLET_W > b4_xpos &&
                        abullet_x < b4_xpos + BARRIER_WIDTH &&
                        abullet_y + BULLET_H > BARRIER_Y &&
                        abullet_y < BARRIER_Y + BARRIER_HEIGHT) begin
                            barrier_health[3] <= barrier_health[3] - 1;
                            abullet_active <= 0;
                    end
          end
		      else begin
			        if (lfsr[0]) begin
              abullet_active <= 1;

              // Extract rowRand and colRand from LFSR
              selectedRowRand <= lfsr[3:1];
              if (selectedRowRand > 3'd4) selectedRowRand <= 3'd4;
              colRand <= lfsr[6:4]; // 0..7

              // Calculate bullet position based on random row and column
              abullet_x <= group_x + (colRand * (SMALL_SIZE + ALIEN_SPACING)) + 8;
              abullet_y <= (selectedRowRand == 3'd0) ? rowY_0 :
                           (selectedRowRand == 3'd1) ? rowY_1 :
                           (selectedRowRand == 3'd2) ? rowY_2 :
                           (selectedRowRand == 3'd3) ? rowY_3 :
                                                       rowY_4; 
		    end
		  end
		  
		  if (shooter_lives == 0) begin
		      game_over <= 1;
		  end
      else begin
          game_over <= 0;
      end
		  
    end

    if (pix_y == 0 && prev_vpos != 0) begin
                if (pb_active) begin
                    if (aliens_alive[0][0] &&
                        pb_x + BULLET_W > s1_x &&
                        pb_x < s1_x + SMALL_SIZE &&
                        pb_y + BULLET_H > SMALL_Y &&
                        pb_y < SMALL_Y + SMALL_SIZE) begin
                            aliens_alive[0][0] <= 0;
                            pb_active <= 0;
                            score <= score + 30;
                    end
                    // Alien [0][1]
                    if (aliens_alive[0][1] &&
                        pb_x + BULLET_W > s2_x &&
                        pb_x < s2_x + SMALL_SIZE &&
                        pb_y + BULLET_H > SMALL_Y &&
                        pb_y < SMALL_Y + SMALL_SIZE) begin
                            aliens_alive[0][1] <= 0;
                            pb_active <= 0;
                            score <= score + 30;
                    end

                    // Alien [0][2]
                    if (aliens_alive[0][2] &&
                        pb_x + BULLET_W > s3_x &&
                        pb_x < s3_x + SMALL_SIZE &&
                        pb_y + BULLET_H > SMALL_Y &&
                        pb_y < SMALL_Y + SMALL_SIZE) begin
                            aliens_alive[0][2] <= 0;
                            pb_active <= 0;
                            score <= score + 30;
                    end

                    // Alien [0][3]
                    if (aliens_alive[0][3] &&
                        pb_x + BULLET_W > s4_x &&
                        pb_x < s4_x + SMALL_SIZE &&
                        pb_y + BULLET_H > SMALL_Y &&
                        pb_y < SMALL_Y + SMALL_SIZE) begin
                            aliens_alive[0][3] <= 0;
                            pb_active <= 0;
                            score <= score + 30;
                    end

                    // Alien [0][4]
                    if (aliens_alive[0][4] &&
                        pb_x + BULLET_W > s5_x &&
                        pb_x < s5_x + SMALL_SIZE &&
                        pb_y + BULLET_H > SMALL_Y &&
                        pb_y < SMALL_Y + SMALL_SIZE) begin
                            aliens_alive[0][4] <= 0;
                            pb_active <= 0;
                            score <= score + 30;
                    end

                    // Alien [0][5]
                    if (aliens_alive[0][5] &&
                        pb_x + BULLET_W > s6_x &&
                        pb_x < s6_x + SMALL_SIZE &&
                        pb_y + BULLET_H > SMALL_Y &&
                        pb_y < SMALL_Y + SMALL_SIZE) begin
                            aliens_alive[0][5] <= 0;
                            pb_active <= 0;
                            score <= score + 30;
                    end

                    // Alien [0][6]
                    if (aliens_alive[0][6] &&
                        pb_x + BULLET_W > s7_x &&
                        pb_x < s7_x + SMALL_SIZE &&
                        pb_y + BULLET_H > SMALL_Y &&
                        pb_y < SMALL_Y + SMALL_SIZE) begin
                            aliens_alive[0][6] <= 0;
                            pb_active <= 0;
                            score <= score + 30;
                    end

                    // Alien [0][7]
                    if (aliens_alive[0][7] &&
                        pb_x + BULLET_W > s8_x &&
                        pb_x < s8_x + SMALL_SIZE &&
                        pb_y + BULLET_H > SMALL_Y &&
                        pb_y < SMALL_Y + SMALL_SIZE) begin
                            aliens_alive[0][7] <= 0;
                            pb_active <= 0;
                            score <= score + 30;
                    end

                    // Similarly, check for Aliens in other rows (Medium and Large)
                    // Medium Row 1: Aliens [1][0] to [1][7] (mA1 to mA8)
                    if (aliens_alive[1][0] &&
                        pb_x + BULLET_W > mA1_x &&
                        pb_x < mA1_x + MEDIUM_SIZE &&
                        pb_y + BULLET_H > MEDIUM_Y1 &&
                        pb_y < MEDIUM_Y1 + MEDIUM_SIZE) begin
                            aliens_alive[1][0] <= 0;
                            pb_active <= 0;
                            score <= score + 20;
                    end

                    if (aliens_alive[1][1] &&
                        pb_x + BULLET_W > mA2_x &&
                        pb_x < mA2_x + MEDIUM_SIZE &&
                        pb_y + BULLET_H > MEDIUM_Y1 &&
                        pb_y < MEDIUM_Y1 + MEDIUM_SIZE) begin
                            aliens_alive[1][1] <= 0;
                            pb_active <= 0;
                            score <= score + 20;
                    end

                    if (aliens_alive[1][2] &&
                        pb_x + BULLET_W > mA3_x &&
                        pb_x < mA3_x + MEDIUM_SIZE &&
                        pb_y + BULLET_H > MEDIUM_Y1 &&
                        pb_y < MEDIUM_Y1 + MEDIUM_SIZE) begin
                            aliens_alive[1][2] <= 0;
                            pb_active <= 0;
                            score <= score + 20;
                    end

                    if (aliens_alive[1][3] &&
                        pb_x + BULLET_W > mA4_x &&
                        pb_x < mA4_x + MEDIUM_SIZE &&
                        pb_y + BULLET_H > MEDIUM_Y1 &&
                        pb_y < MEDIUM_Y1 + MEDIUM_SIZE) begin
                            aliens_alive[1][3] <= 0;
                            pb_active <= 0;
                            score <= score + 20;
                    end

                    if (aliens_alive[1][4] &&
                        pb_x + BULLET_W > mA5_x &&
                        pb_x < mA5_x + MEDIUM_SIZE &&
                        pb_y + BULLET_H > MEDIUM_Y1 &&
                        pb_y < MEDIUM_Y1 + MEDIUM_SIZE) begin
                            aliens_alive[1][4] <= 0;
                            pb_active <= 0;
                            score <= score + 20;
                    end

                    if (aliens_alive[1][5] &&
                        pb_x + BULLET_W > mA6_x &&
                        pb_x < mA6_x + MEDIUM_SIZE &&
                        pb_y + BULLET_H > MEDIUM_Y1 &&
                        pb_y < MEDIUM_Y1 + MEDIUM_SIZE) begin
                            aliens_alive[1][5] <= 0;
                            pb_active <= 0;
                            score <= score + 20;
                    end

                    if (aliens_alive[1][6] &&
                        pb_x + BULLET_W > mA7_x &&
                        pb_x < mA7_x + MEDIUM_SIZE &&
                        pb_y + BULLET_H > MEDIUM_Y1 &&
                        pb_y < MEDIUM_Y1 + MEDIUM_SIZE) begin
                            aliens_alive[1][6] <= 0;
                            pb_active <= 0;
                            score <= score + 20;
                    end

                    if (aliens_alive[1][7] &&
                        pb_x + BULLET_W > mA8_x &&
                        pb_x < mA8_x + MEDIUM_SIZE &&
                        pb_y + BULLET_H > MEDIUM_Y1 &&
                        pb_y < MEDIUM_Y1 + MEDIUM_SIZE) begin
                            aliens_alive[1][7] <= 0;
                            pb_active <= 0;
                            score <= score + 20;
                    end

                    ////
                    if (aliens_alive[2][0] &&
                        pb_x + BULLET_W > mB1_x &&
                        pb_x < mB1_x + MEDIUM_SIZE &&
                        pb_y + BULLET_H > MEDIUM_Y2 &&
                        pb_y < MEDIUM_Y2 + MEDIUM_SIZE) begin
                            aliens_alive[2][0] <= 0;
                            pb_active <= 0;
                            score <= score + 20;
                    end

                    if (aliens_alive[2][1] &&
                        pb_x + BULLET_W > mB2_x &&
                        pb_x < mB2_x + MEDIUM_SIZE &&
                        pb_y + BULLET_H > MEDIUM_Y2 &&
                        pb_y < MEDIUM_Y2 + MEDIUM_SIZE) begin
                            aliens_alive[2][1] <= 0;
                            pb_active <= 0;
                            score <= score + 20;
                    end

                    if (aliens_alive[2][2] &&
                        pb_x + BULLET_W > mB3_x &&
                        pb_x < mB3_x + MEDIUM_SIZE &&
                        pb_y + BULLET_H > MEDIUM_Y2 &&
                        pb_y < MEDIUM_Y2 + MEDIUM_SIZE) begin
                            aliens_alive[2][2] <= 0;
                            pb_active <= 0;
                            score <= score + 20;
                    end

                    if (aliens_alive[2][3] &&
                        pb_x + BULLET_W > mB4_x &&
                        pb_x < mB4_x + MEDIUM_SIZE &&
                        pb_y + BULLET_H > MEDIUM_Y2 &&
                        pb_y < MEDIUM_Y2 + MEDIUM_SIZE) begin
                            aliens_alive[2][3] <= 0;
                            pb_active <= 0;
                            score <= score + 20;
                    end

                    if (aliens_alive[2][4] &&
                        pb_x + BULLET_W > mB5_x &&
                        pb_x < mB5_x + MEDIUM_SIZE &&
                        pb_y + BULLET_H > MEDIUM_Y2 &&
                        pb_y < MEDIUM_Y2 + MEDIUM_SIZE) begin
                            aliens_alive[2][4] <= 0;
                            pb_active <= 0;
                            score <= score + 20;
                    end

                    if (aliens_alive[2][5] &&
                        pb_x + BULLET_W > mB6_x &&
                        pb_x < mB6_x + MEDIUM_SIZE &&
                        pb_y + BULLET_H > MEDIUM_Y2 &&
                        pb_y < MEDIUM_Y2 + MEDIUM_SIZE) begin
                            aliens_alive[2][5] <= 0;
                            pb_active <= 0;
                            score <= score + 20;
                    end

                    if (aliens_alive[2][6] &&
                        pb_x + BULLET_W > mB7_x &&
                        pb_x < mB7_x + MEDIUM_SIZE &&
                        pb_y + BULLET_H > MEDIUM_Y2 &&
                        pb_y < MEDIUM_Y2 + MEDIUM_SIZE) begin
                            aliens_alive[2][6] <= 0;
                            pb_active <= 0;
                            score <= score + 20;
                    end

                    if (aliens_alive[2][7] &&
                        pb_x + BULLET_W > mB8_x &&
                        pb_x < mB8_x + MEDIUM_SIZE &&
                        pb_y + BULLET_H > MEDIUM_Y2 &&
                        pb_y < MEDIUM_Y2 + MEDIUM_SIZE) begin
                            aliens_alive[2][7] <= 0;
                            pb_active <= 0;
                            score <= score + 20;
                    end

                    ////
                    if (aliens_alive[3][0] &&
                        pb_x + BULLET_W > lA1_x &&
                        pb_x < lA1_x + MEDIUM_SIZE &&
                        pb_y + BULLET_H > LARGE_Y1 &&
                        pb_y < LARGE_Y1 + MEDIUM_SIZE) begin
                            aliens_alive[3][0] <= 0;
                            pb_active <= 0;
                            score <= score + 10;
                    end

                    if (aliens_alive[3][1] &&
                        pb_x + BULLET_W > lA2_x &&
                        pb_x < lA2_x + MEDIUM_SIZE &&
                        pb_y + BULLET_H > LARGE_Y1 &&
                        pb_y < LARGE_Y1 + MEDIUM_SIZE) begin
                            aliens_alive[3][1] <= 0;
                            pb_active <= 0;
                            score <= score + 10;
                    end

                    if (aliens_alive[3][2] &&
                        pb_x + BULLET_W > lA3_x &&
                        pb_x < lA3_x + MEDIUM_SIZE &&
                        pb_y + BULLET_H > LARGE_Y1 &&
                        pb_y < LARGE_Y1 + MEDIUM_SIZE) begin
                            aliens_alive[3][2] <= 0;
                            pb_active <= 0;
                            score <= score + 10;
                    end

                    if (aliens_alive[3][3] &&
                        pb_x + BULLET_W > lA4_x &&
                        pb_x < lA4_x + MEDIUM_SIZE &&
                        pb_y + BULLET_H > LARGE_Y1 &&
                        pb_y < LARGE_Y1 + MEDIUM_SIZE) begin
                            aliens_alive[3][3] <= 0;
                            pb_active <= 0;
                            score <= score + 10;
                    end

                    if (aliens_alive[3][4] &&
                        pb_x + BULLET_W > lA5_x &&
                        pb_x < lA5_x + MEDIUM_SIZE &&
                        pb_y + BULLET_H > LARGE_Y1 &&
                        pb_y < LARGE_Y1 + MEDIUM_SIZE) begin
                            aliens_alive[3][4] <= 0;
                            pb_active <= 0;
                            score <= score + 10;
                    end

                    if (aliens_alive[3][5] &&
                        pb_x + BULLET_W > lA6_x &&
                        pb_x < lA6_x + MEDIUM_SIZE &&
                        pb_y + BULLET_H > LARGE_Y1 &&
                        pb_y < LARGE_Y1 + MEDIUM_SIZE) begin
                            aliens_alive[3][5] <= 0;
                            pb_active <= 0;
                            score <= score + 10;
                    end

                    if (aliens_alive[3][6] &&
                        pb_x + BULLET_W > lA7_x &&
                        pb_x < lA7_x + MEDIUM_SIZE &&
                        pb_y + BULLET_H > LARGE_Y1 &&
                        pb_y < LARGE_Y1 + MEDIUM_SIZE) begin
                            aliens_alive[3][6] <= 0;
                            pb_active <= 0;
                            score <= score + 10;
                    end

                    if (aliens_alive[3][7] &&
                        pb_x + BULLET_W > lA8_x &&
                        pb_x < lA8_x + MEDIUM_SIZE &&
                        pb_y + BULLET_H > LARGE_Y1 &&
                        pb_y < LARGE_Y1 + MEDIUM_SIZE) begin
                            aliens_alive[3][7] <= 0;
                            pb_active <= 0;
                            score <= score + 10;
                    end
                  

                     ////
                    if (aliens_alive[4][0] &&
                        pb_x + BULLET_W > lB1_x &&
                        pb_x < lB1_x + MEDIUM_SIZE &&
                        pb_y + BULLET_H > LARGE_Y2 &&
                        pb_y < LARGE_Y2 + MEDIUM_SIZE) begin
                            aliens_alive[4][0] <= 0;
                            pb_active <= 0;
                            score <= score + 10;
                    end

                    if (aliens_alive[4][1] &&
                        pb_x + BULLET_W > lB2_x &&
                        pb_x < lB2_x + MEDIUM_SIZE &&
                        pb_y + BULLET_H > LARGE_Y2 &&
                        pb_y < LARGE_Y2 + MEDIUM_SIZE) begin
                            aliens_alive[4][1] <= 0;
                            pb_active <= 0;
                            score <= score + 10;
                    end

                    if (aliens_alive[4][2] &&
                        pb_x + BULLET_W > lB3_x &&
                        pb_x < lB3_x + MEDIUM_SIZE &&
                        pb_y + BULLET_H > LARGE_Y2 &&
                        pb_y < LARGE_Y2 + MEDIUM_SIZE) begin
                            aliens_alive[4][2] <= 0;
                            pb_active <= 0;
                            score <= score + 10;
                    end

                    if (aliens_alive[4][3] &&
                        pb_x + BULLET_W > lB4_x &&
                        pb_x < lB4_x + MEDIUM_SIZE &&
                        pb_y + BULLET_H > LARGE_Y2 &&
                        pb_y < LARGE_Y2 + MEDIUM_SIZE) begin
                            aliens_alive[4][3] <= 0;
                            pb_active <= 0;
                            score <= score + 10;
                    end

                    if (aliens_alive[4][4] &&
                        pb_x + BULLET_W > lB5_x &&
                        pb_x < lB5_x + MEDIUM_SIZE &&
                        pb_y + BULLET_H > LARGE_Y2 &&
                        pb_y < LARGE_Y2 + MEDIUM_SIZE) begin
                            aliens_alive[4][4] <= 0;
                            pb_active <= 0;
                            score <= score + 10;
                    end

                    if (aliens_alive[4][5] &&
                        pb_x + BULLET_W > lB6_x &&
                        pb_x < lB6_x + MEDIUM_SIZE &&
                        pb_y + BULLET_H > LARGE_Y2 &&
                        pb_y < LARGE_Y2 + MEDIUM_SIZE) begin
                            aliens_alive[4][5] <= 0;
                            pb_active <= 0;
                            score <= score + 10;
                    end

                    if (aliens_alive[4][6] &&
                        pb_x + BULLET_W > lB7_x &&
                        pb_x < lB7_x + MEDIUM_SIZE &&
                        pb_y + BULLET_H > LARGE_Y2 &&
                        pb_y < LARGE_Y2 + MEDIUM_SIZE) begin
                            aliens_alive[4][6] <= 0;
                            pb_active <= 0;
                            score <= score + 10;
                    end

                    if (aliens_alive[4][7] &&
                        pb_x + BULLET_W > lB8_x &&
                        pb_x < lB8_x + MEDIUM_SIZE &&
                        pb_y + BULLET_H > LARGE_Y2 &&
                        pb_y < LARGE_Y2 + MEDIUM_SIZE) begin
                            aliens_alive[4][7] <= 0;
                            pb_active <= 0;
                            score <= score + 10;
                    end

                    

                    // Repeat similar blocks for aliens_alive[1][1] to aliens_alive[4][7]
                    // Player Bullet 0 vs. Barriers
                    // Barrier 0
                    if (barrier_health[0] > 0 &&
                        pb_x + BULLET_W > b1_xpos &&
                        pb_x < b1_xpos + BARRIER_WIDTH &&
                        pb_y + BULLET_H > BARRIER_Y &&
                        pb_y < BARRIER_Y + BARRIER_HEIGHT) begin
                            barrier_health[0] <= barrier_health[0] - 1;
                            pb_active <= 0;
                    end

                    // Barrier 1
                    if (barrier_health[1] > 0 &&
                        pb_x + BULLET_W > b2_xpos &&
                        pb_x < b2_xpos + BARRIER_WIDTH &&
                        pb_y + BULLET_H > BARRIER_Y &&
                        pb_y < BARRIER_Y + BARRIER_HEIGHT) begin
                            barrier_health[1] <= barrier_health[1] - 1;
                            pb_active <= 0;
                    end

                    // Barrier 2
                    if (barrier_health[2] > 0 &&
                        pb_x + BULLET_W > b3_xpos &&
                        pb_x < b3_xpos + BARRIER_WIDTH &&
                        pb_y + BULLET_H > BARRIER_Y &&
                        pb_y < BARRIER_Y + BARRIER_HEIGHT) begin
                            barrier_health[2] <= barrier_health[2] - 1;
                            pb_active <= 0;
                        end

                    // Barrier 3
                    if (barrier_health[3] > 0 &&
                        pb_x + BULLET_W > b4_xpos &&
                        pb_x < b4_xpos + BARRIER_WIDTH &&
                        pb_y + BULLET_H > BARRIER_Y &&
                        pb_y < BARRIER_Y + BARRIER_HEIGHT) begin
                            barrier_health[3] <= barrier_health[3] - 1;
                            pb_active <= 0;
                    end
                end
            
        
    

  
            
                
      end
    end

    if (score == 720) begin
      game_won <= 1;
    end
    else begin
      game_won <= 0;
    end
  end







// draw alien bullet (2 wide x 6 tall, red)
    wire abullet_on;
    localparam BULLET_W = 2;
    localparam BULLET_H = 6;
    assign abullet_on = abullet_active &&
                        (pix_x >= abullet_x) && (pix_x < abullet_x + BULLET_W) &&
                        (pix_y >= abullet_y) && (pix_y < abullet_y + BULLET_H);


    // Draw them (2×6). We'll do 4 separate signals, then combine them.
    wire bullet0_on = pb_active &&
                      (pix_x >= pb_x) && (pix_x < pb_x + 2) &&
                      (pix_y >= pb_y) && (pix_y < pb_y + 6);

    
    // Combined “player bullet on” signal if ANY bullet is on at pixel
    wire bullet_on = (bullet0_on);

    
    //-----------------------------------
    wire pixel_on_score;
   draw_score draw_score_inst (
        .pix_x(pix_x),                   // Current pixel's X coordinate
        .pix_y(pix_y),                   // Current pixel's Y coordinate
        .score(score),               // Player's current score
        .shooter_lives(shooter_lives), // Shooter's current lives
        .pixel_on(pixel_on_score)        // Output: Pixel part of score or health display
    );

    //----------------------------------
  
 
    //----------------------------------------------------
    // 14) Final Color Priority with Collision Effects
    //----------------------------------------------------
    wire [5:0] color_small   = 6'b001100;  
    wire [5:0] color_medium  = 6'b110011;  
    wire [5:0] color_large   = 6'b111100;  
    wire [5:0] color_shooter = 6'b011101; 
    wire [5:0] color_barrier = 6'b011101; 
    wire [5:0] color_bullet  = 6'b111111; 
    wire [5:0] color_alien_bullet = 6'b110000; 
    wire [5:0] color_trophy = 6'b101001;
    wire [5:0] color_heart = 6'b110000;
    wire [5:0] color_score  = 6'b111111;

    always @(posedge clk) begin
      if (~rst_n) begin
        R <= 0;
        G <= 0;
        B <= 0;
      end else begin
        // Default black
        R <= 0;
        G <= 0;
        B <= 0;

        if (video_active) begin
          // Priority: alien bullet > player bullets > shooter > barrier > large > medium > small
          if (pixel_on_score) begin
            R <= color_score[5:4];
            G <= color_score[3:2];
            B <= color_score[1:0];
          end
          else if (pixel_on_trophy) begin
            R <= color_trophy[5:4];
            G <= color_trophy[3:2];
            B <= color_trophy[1:0];
          end
          else if (pixel_on_heart) begin
            R <= color_heart[5:4];
            G <= color_heart[3:2];
            B <= color_heart[1:0];
          end
          else if (abullet_on) begin
            R <= color_alien_bullet[5:4];
            G <= color_alien_bullet[3:2];
            B <= color_alien_bullet[1:0];
          end
          else if (bullet_on) begin
            R <= color_bullet[5:4];
            G <= color_bullet[3:2];
            B <= color_bullet[1:0];
          end
          else if (shooter_on) begin
            R <= color_shooter[5:4];
            G <= color_shooter[3:2];
            B <= color_shooter[1:0];
          end
          else if (any_barrier_on) begin
            R <= color_barrier[5:4];
            G <= color_barrier[3:2];
            B <= color_barrier[1:0];
          end
          else if (any_large_on) begin
            R <= color_large[5:4];
            G <= color_large[3:2];
            B <= color_large[1:0];
          end
          else if (any_medium_on) begin
            R <= color_medium[5:4];
            G <= color_medium[3:2];
            B <= color_medium[1:0];
          end
          else if (any_small_on) begin
            R <= color_small[5:4];
            G <= color_small[3:2];
            B <= color_small[1:0];
          end
        end
      end
    end



endmodule

module vga_sync_generator (
    input  wire clk,
    input  wire reset,
    output reg  hsync,
    output reg  vsync,
    output wire display_on,
    output reg  [9:0] hpos,
    output reg  [9:0] vpos
);
    parameter H_DISPLAY = 640;
    parameter H_BACK    = 48;
    parameter H_FRONT   = 16;
    parameter H_SYNC    = 96;
    parameter V_DISPLAY = 480;
    parameter V_TOP     = 33;
    parameter V_BOTTOM  = 10;
    parameter V_SYNC    = 2;

    localparam H_SYNC_START = H_DISPLAY + H_FRONT;
    localparam H_SYNC_END   = H_DISPLAY + H_FRONT + H_SYNC - 1;
    localparam H_MAX        = H_DISPLAY + H_BACK + H_FRONT + H_SYNC - 1;
    localparam V_SYNC_START = V_DISPLAY + V_BOTTOM;
    localparam V_SYNC_END   = V_DISPLAY + V_BOTTOM + V_SYNC - 1;
    localparam V_MAX        = V_DISPLAY + V_TOP + V_BOTTOM + V_SYNC - 1;

    wire hmaxxed = (hpos == H_MAX) || reset;
    wire vmaxxed = (vpos == V_MAX) || reset;

    always @(posedge clk) begin
        if (reset) begin
            hpos  <= 0;
            hsync <= 0;
        end else begin
            if (hmaxxed) 
                hpos <= 0;
            else
                hpos <= hpos + 1;

            hsync <= (hpos >= H_SYNC_START && hpos <= H_SYNC_END);
        end
    end

    always @(posedge clk) begin
        if (reset) begin
            vpos  <= 0;
            vsync <= 0;
        end else if (hmaxxed) begin
            if (vmaxxed)
                vpos <= 0;
            else
                vpos <= vpos + 1;

            vsync <= (vpos >= V_SYNC_START && vpos <= V_SYNC_END);
        end
    end

    assign display_on = (hpos < H_DISPLAY) && (vpos < V_DISPLAY);
endmodule


`default_nettype none
module draw_small_alien (
    input  wire [9:0] pix_x,
    input  wire [9:0] pix_y,
    input  wire [9:0] alien_left_x,
    input  wire [9:0] alien_top_y,
    output wire       pixel_on
);
    wire [9:0] x_off = pix_x - alien_left_x;
    wire [9:0] y_off = pix_y - alien_top_y;

    // Check if inside 16×16 box
    wire insider = (x_off[9:4] == 0) && (y_off[9:4] == 0);

    wire [3:0] ry = y_off[3:0];
    wire [15:0] row_bits;
    small_alien_rom s_rom(
        .row_index(ry),
        .row_data(row_bits)
    );

    wire [3:0] rx = x_off[3:0];
    wire bit_on = row_bits[rx];

    assign pixel_on = insider && bit_on;
endmodule


`default_nettype none
module draw_medium_alien (
    input  wire [9:0] pix_x,
    input  wire [9:0] pix_y,
    input  wire [9:0] alien_left_x,
    input  wire [9:0] alien_top_y,
    output wire       pixel_on
);
    wire [9:0] x_off = pix_x - alien_left_x;
    wire [9:0] y_off = pix_y - alien_top_y;

    wire insider = (x_off[9:4] == 0) && (y_off[9:4] == 0);

    wire [3:0] ry = y_off[3:0];
    wire [15:0] row_bits;
    medium_alien_rom med_rom(
        .row_index(ry),
        .row_data(row_bits)
    );

    wire [3:0] rx = x_off[3:0];
    wire bit_on = row_bits[rx];

    assign pixel_on = insider && bit_on;
endmodule

`default_nettype none
module draw_alien3 (
    input  wire [9:0] pix_x,
    input  wire [9:0] pix_y,
    input  wire [9:0] alien_left_x,
    input  wire [9:0] alien_top_y,
    output wire       pixel_on
);
    wire [9:0] x_off = pix_x - alien_left_x;
    wire [9:0] y_off = pix_y - alien_top_y;

    wire insider = (x_off[9:4] == 0 && y_off[9:4] == 0);

    wire [3:0] ry = y_off[3:0];
    wire [15:0] row_bits;
    alien3_rom large_rom(
        .row_index(ry),
        .row_data(row_bits)
    );

    wire [3:0] rx = x_off[3:0];
    wire bit_on  = row_bits[rx];

    assign pixel_on = insider && bit_on;
endmodule

`default_nettype none
module draw_shooter (
    input  wire [9:0] pix_x,
    input  wire [9:0] pix_y,
    input  wire [9:0] shooter_left_x,
    input  wire [9:0] shooter_top_y,
    output wire       pixel_on
);
    wire [9:0] x_off = pix_x - shooter_left_x;
    wire [9:0] y_off = pix_y - shooter_top_y;

    // Are we within the 16×16 bounding box?
    wire insider = (x_off[9:4] == 0) && (y_off[9:4] == 0);

    wire [3:0] row_addr = y_off[3:0];
    wire [15:0] row_bits;
    shooter_rom srom(.row_index(row_addr), .row_data(row_bits));

    wire [3:0] col_addr = x_off[3:0];
    wire bit_on = row_bits[col_addr];

    assign pixel_on = insider && bit_on;
endmodule

`default_nettype none
module alien3_rom(
    input  wire [3:0]  row_index,
    output wire [15:0] row_data
);
    reg [15:0] rom_array[0:15];
    initial begin
      // Example 16×16 large alien
      rom_array[0]  = 16'b0010011111100100;
      rom_array[1]  = 16'b0001111111111000;
      rom_array[2]  = 16'b0011101101101100;
      rom_array[3]  = 16'b0011111111111100;
      rom_array[4]  = 16'b0001111111111000;
      rom_array[5]  = 16'b0001010010010000;
      rom_array[6]  = 16'b0000100000110000;
      rom_array[7]  = 16'b1111000000011111;
      rom_array[8]  = 16'b0011100000110000;
      rom_array[9]  = 16'b0001111111110000;
      rom_array[10] = 16'b0001111111110000;
      rom_array[11] = 16'b0010000000001000;
      rom_array[12] = 16'b0100000000000100;
      rom_array[13] = 16'b0000000000000000;
      rom_array[14] = 16'b0000000000000000;
      rom_array[15] = 16'b0000000000000000;
    end
    assign row_data = rom_array[row_index];
endmodule


`default_nettype none
module medium_alien_rom(
    input  wire [3:0]  row_index,
    output wire [15:0] row_data
);
    reg [15:0] rom_array[0:15];
    initial begin
      rom_array[0]  = 16'b0000000000000000;
      rom_array[1]  = 16'b0000000000000000;
      rom_array[2]  = 16'b0000001111000000;
      rom_array[3]  = 16'b0000011111100000;
      rom_array[4]  = 16'b0001111111111000;
      rom_array[5]  = 16'b0011101111011100;
      rom_array[6]  = 16'b0111111111111100;
      rom_array[7]  = 16'b0111111111111110;
      rom_array[8]  = 16'b1111111111111111;
      rom_array[9]  = 16'b1111111111111111;
      rom_array[10] = 16'b1001111111100001;
      rom_array[11] = 16'b0000110011000000;
      rom_array[12] = 16'b0001100001100000;
      rom_array[13] = 16'b0011000000110000;
      rom_array[14] = 16'b0110000000011000;
      rom_array[15] = 16'b1100000000001100;
    end
    assign row_data = rom_array[row_index];
endmodule


`default_nettype none
module shooter_rom(
    input  wire [3:0]  row_index,
    output wire [15:0] row_data
);
    reg [15:0] rom_array[0:15];
    initial begin
        // A simple 16×16 “tank” or “ship”-like pattern.
        rom_array[ 0] = 16'b0000000110000000;
        rom_array[ 1] = 16'b0000001111000000;
        rom_array[ 2] = 16'b0000001111000000;
        rom_array[ 3] = 16'b0000001111000000;
        rom_array[ 4] = 16'b0000111111110000;
        rom_array[ 5] = 16'b0000111111110000;
        rom_array[ 6] = 16'b0000111111110000;
        rom_array[ 7] = 16'b0000111111110000;
        rom_array[ 8] = 16'b0001111111111000;
        rom_array[ 9] = 16'b0011111111111100;
        rom_array[10] = 16'b0111111111111110;
        rom_array[11] = 16'b1111111111111111;
        rom_array[12] = 16'b1111111111111111;
        rom_array[13] = 16'b1111100000011111;
        rom_array[14] = 16'b0000000000000000;
        rom_array[15] = 16'b0000000000000000;
    end
    assign row_data = rom_array[row_index];
endmodule

`default_nettype none
module small_alien_rom(
    input  wire [3:0]  row_index,   // 0..15
    output wire [15:0] row_data
);
// >>> Module Implementation Begin

// <<< Module Implementation End
endmodule






`default_nettype none
module barrier_rom(
    input  wire [3:0] row_index,   
    output wire [31:0] row_data    
);
    reg [31:0] rom_array [0:15];
    initial begin
        // Example barrier pattern. Customize as needed.
        rom_array[0]  = 32'b00000111111111111111111111100000;
        rom_array[1]  = 32'b00001111111111111111111111110000;
        rom_array[2]  = 32'b00011111111111111111111111111000;
        rom_array[3]  = 32'b00111111111111111111111111111100;
        rom_array[4]  = 32'b01111111111111111111111111111110;
        rom_array[5]  = 32'b11111111111111111111111111111111;
        rom_array[6]  = 32'b11111111111111111111111111111111;
        rom_array[7]  = 32'b11111111111111111111111111111111;
        rom_array[8]  = 32'b11111111111111111111111111111111;
        rom_array[9]  = 32'b11111111111111111111111111111111;
        rom_array[10] = 32'b11111111111111111111111111111111;
        rom_array[11] = 32'b11111111111111111111111111111111;
        rom_array[12] = 32'b11111111111111111111111111111111;
        rom_array[13] = 32'b11111111100000000000000111111111;
        rom_array[14] = 32'b11111111000000000000000011111111;
        rom_array[15] = 32'b11111110000000000000000001111111;
    end
    assign row_data = rom_array[row_index];
endmodule

`default_nettype none
module draw_barrier(
    input  wire [9:0] pix_x,
    input  wire [9:0] pix_y,
    input  wire [9:0] bar_left_x,
    input  wire [9:0] bar_top_y,
    output wire       pixel_on
);
    // 32 wide x 16 tall
    wire [9:0] x_off = pix_x - bar_left_x;
    wire [9:0] y_off = pix_y - bar_top_y;

    wire insider = (x_off[9:5] == 0) && (y_off[9:4] == 0);

    wire [3:0] row_idx = y_off[3:0];
    wire [31:0] row_bits;
    barrier_rom bar_rom(.row_index(row_idx), .row_data(row_bits));

    wire [4:0] col_idx = x_off[4:0];
    wire bit_on = row_bits[col_idx];

    assign pixel_on = insider && bit_on;
endmodule



`default_nettype none
module heart_rom(
    input  wire [3:0] row_index,   // Row index (0 to 15)
    output wire [15:0] row_data    // Pixel data for the row
);
    reg [15:0] rom_array [0:15];
    
    initial begin
        // 16x16 Heart sprite
        rom_array[0]  = 16'b0000000000000000;
        rom_array[1]  = 16'b0000000000000000;
        rom_array[2]  = 16'b0001110001110000;
        rom_array[3]  = 16'b0011111011111000;
        rom_array[4]  = 16'b0011111111111000;
        rom_array[5]  = 16'b0011111111111000;
        rom_array[6]  = 16'b0001111111110000;
        rom_array[7]  = 16'b0000111111100000;
        rom_array[8]  = 16'b0000011111000000;
        rom_array[9]  = 16'b0000001110000000;
        rom_array[10] = 16'b0000000100000000;
        rom_array[11] = 16'b0000000000000000;
        rom_array[12] = 16'b0000000000000000;
        rom_array[13] = 16'b0000000000000000;
        rom_array[14] = 16'b0000000000000000;
        rom_array[15] = 16'b0000000000000000;
    end
    
    assign row_data = rom_array[row_index];
endmodule


`default_nettype none
module draw_heart(
    input  wire [9:0] pix_x,          // Current pixel's X coordinate
    input  wire [9:0] pix_y,          // Current pixel's Y coordinate
    input  wire [9:0] heart_left_x,   // Heart sprite's top-left X position
    input  wire [9:0] heart_top_y,    // Heart sprite's top-left Y position
    output wire       pixel_on         // Output signal indicating if pixel is part of the heart
);
    
    wire [9:0] x_off = pix_x - heart_left_x;
    wire [9:0] y_off = pix_y - heart_top_y;

   
    wire insider = (x_off[9:4] == 0) && (y_off[9:4] == 0); 

    
    wire [3:0] row_idx = y_off[3:0];              
    wire [15:0] row_bits;
    heart_rom heart_rom_inst (
        .row_index(row_idx),
        .row_data(row_bits)
    );

    
    wire [3:0] col_idx = x_off[3:0];              // Column index (0 to 15)
    wire bit_on = row_bits[col_idx];               // Pixel status in the current row

    // Assign the output signal based on whether the pixel is part of the heart
    assign pixel_on = insider && bit_on;
endmodule


`default_nettype none
module trophy_rom(
    input  wire [3:0] row_index,   // Row index (0 to 15)
    output wire [15:0] row_data    // Pixel data for the row
);
    reg [15:0] rom_array [0:15];
    
    initial begin
        // 16x16 Trophy sprite
        rom_array[0]  = 16'b0000000000000000;
        rom_array[1]  = 16'b0000000000000000;
        rom_array[2]  = 16'b0000000000000000;
        rom_array[3]  = 16'b0000000000000000;
        rom_array[4]  = 16'b0000000000000000;
        rom_array[5]  = 16'b0000000000000000;
        rom_array[6]  = 16'b0011111111111100;
        rom_array[7]  = 16'b0011111111111100;
        rom_array[8]  = 16'b0011111111111100;
        rom_array[9]  = 16'b0011111111111100;
        rom_array[10] = 16'b0011111111111100;
        rom_array[11] = 16'b0001111111111000;
        rom_array[12] = 16'b0000011111100000;
        rom_array[13] = 16'b0000011111100000;
        rom_array[14] = 16'b0000011111100000;
        rom_array[15] = 16'b0000111111110000;
    end
    
    assign row_data = rom_array[row_index];
endmodule


`default_nettype none
module draw_trophy(
    input  wire [9:0] pix_x,           // Current pixel's X coordinate
    input  wire [9:0] pix_y,           // Current pixel's Y coordinate
    input  wire [9:0] trophy_left_x,   // Trophy sprite's top-left X position
    input  wire [9:0] trophy_top_y,    // Trophy sprite's top-left Y position
    output wire       pixel_on          // Output signal indicating if pixel is part of the trophy
);
    // Calculate pixel offsets relative to the Trophy sprite's position
    wire [9:0] x_off = pix_x - trophy_left_x;
    wire [9:0] y_off = pix_y - trophy_top_y;

    // Determine if the current pixel is within the Trophy sprite's boundaries (16x16)
    wire insider = (x_off[9:4] == 0) && (y_off[9:4] == 0); // x_off < 16 and y_off < 16

    // Extract the row index and corresponding pixel data from the ROM
    wire [3:0] row_idx = y_off[3:0];              // Row index (0 to 15)
    wire [15:0] row_bits;
    trophy_rom trophy_rom_inst (
        .row_index(row_idx),
        .row_data(row_bits)
    );

    // Extract the column index and determine if the pixel is active
    wire [3:0] col_idx = x_off[3:0];              // Column index (0 to 15)
    wire bit_on = row_bits[col_idx];               // Pixel status in the current row

    // Assign the output signal based on whether the pixel is part of the trophy
    assign pixel_on = insider && bit_on;
endmodule


`default_nettype none
module segment_rom(
    input  wire [3:0] digit,        // Digit to display (0-9)
    output wire [6:0] segments       // 7 segments: a-g
);
    reg [6:0] rom_array [0:9];

    initial begin
        // Initialize 7-segment patterns for digits 0-9
        rom_array[0] = 7'b0111111;  // 0
        rom_array[1] = 7'b0000110;  // 1
        rom_array[2] = 7'b1011011;  // 2
        rom_array[3] = 7'b1001111;  // 3
        rom_array[4] = 7'b1100110;  // 4
        rom_array[5] = 7'b1101101;  // 5
        rom_array[6] = 7'b1111101;  // 6
        rom_array[7] = 7'b0000111;  // 7
        rom_array[8] = 7'b1111111;  // 8
        rom_array[9] = 7'b1101111;  // 9
    end

    assign segments = rom_array[digit];
endmodule

`default_nettype none
module draw_score(
    input  wire [9:0] pix_x,          // Current pixel's X coordinate
    input  wire [9:0] pix_y,          // Current pixel's Y coordinate
    input  wire [9:0] score,          // Player's score (0-999)
    input  wire [1:0] shooter_lives,  // Shooter's remaining lives (0-9)
    output wire       pixel_on         // Output: 1 if pixel is part of any digit's segment
);
    // Position Parameters
    localparam DIGIT_WIDTH  = 10;    // Width of each digit in pixels
    localparam DIGIT_HEIGHT = 14;    // Height of each digit in pixels

    // Score Digits Positions
    localparam DIGIT2_X = 30;        // X position for Hundreds place (score)
    localparam DIGIT1_X = 60;        // X position for Tens place (score)
    localparam DIGIT0_X = 90;        // X position for Ones place (score)
    localparam DIGIT_Y  = 20;        // Y position for score digits

    // Health Digit Position
    localparam HEALTH_DIGIT_X = 420; // X position for Health digit
    localparam HEALTH_DIGIT_Y = 20;  // Y position for Health digit

    // Registers to hold individual digits
    reg [3:0] digit0, digit1, digit2; // Score digits: ones, tens, hundreds
    reg [3:0] digit_health;            // Health digit

    // Splitting the score and shooter_lives into individual digits
    always @* begin
        digit0 = score % 10;                  // Ones place
        digit1 = (score / 10) % 10;           // Tens place
        digit2 = (score / 100) % 10;          // Hundreds place
        digit_health = shooter_lives;         // Health digit
    end

    // Instantiate Segment ROMs for each digit
    wire [6:0] segments0, segments1, segments2, segments_health;

    segment_rom segment_rom0 (
        .digit(digit0),
        .segments(segments0)
    );

    segment_rom segment_rom1 (
        .digit(digit1),
        .segments(segments1)
    );

    segment_rom segment_rom2 (
        .digit(digit2),
        .segments(segments2)
    );

    segment_rom segment_rom_health (
        .digit(digit_health),
        .segments(segments_health)
    );

    // Function to determine if a pixel is part of any active segment
    function automatic is_pixel_on;
        input [6:0] segments;    // Active segments for the digit
        input [9:0] x_rel;       // X coordinate relative to the digit's top-left corner
        input [9:0] y_rel;       // Y coordinate relative to the digit's top-left corner
        begin
            is_pixel_on = 1'b0;
            // Segment a (top horizontal) - Bit 0
            if (segments[0] && y_rel >= 0 && y_rel < 2 && x_rel >= 2 && x_rel < 8)
                is_pixel_on = 1'b1;
            // Segment b (top-right vertical) - Bit 1
            else if (segments[1] && x_rel >= 8 && x_rel < 10 && y_rel >= 2 && y_rel < 7)
                is_pixel_on = 1'b1;
            // Segment c (bottom-right vertical) - Bit 2
            else if (segments[2] && x_rel >= 8 && x_rel < 10 && y_rel >= 7 && y_rel < 12)
                is_pixel_on = 1'b1;
            // Segment d (bottom horizontal) - Bit 3
            else if (segments[3] && y_rel >= 12 && y_rel < 14 && x_rel >= 2 && x_rel < 8)
                is_pixel_on = 1'b1;
            // Segment e (bottom-left vertical) - Bit 4
            else if (segments[4] && x_rel >= 0 && x_rel < 2 && y_rel >= 7 && y_rel < 12)
                is_pixel_on = 1'b1;
            // Segment f (top-left vertical) - Bit 5
            else if (segments[5] && x_rel >= 0 && x_rel < 2 && y_rel >= 2 && y_rel < 7)
                is_pixel_on = 1'b1;
            // Segment g (middle horizontal) - Bit 6
            else if (segments[6] && y_rel >= 7 && y_rel < 9 && x_rel >= 2 && x_rel < 8)
                is_pixel_on = 1'b1;
        end
    endfunction

    // Determine pixel_on for each digit
    wire seg0_on, seg1_on, seg2_on, seg_health_on;

    // Calculate relative positions for each digit
    wire [9:0] rel_x0 = pix_x - DIGIT0_X;
    wire [9:0] rel_y0 = pix_y - DIGIT_Y;

    wire [9:0] rel_x1 = pix_x - DIGIT1_X;
    wire [9:0] rel_y1 = pix_y - DIGIT_Y;

    wire [9:0] rel_x2 = pix_x - DIGIT2_X;
    wire [9:0] rel_y2 = pix_y - DIGIT_Y;

    wire [9:0] rel_x_health = pix_x - HEALTH_DIGIT_X;
    wire [9:0] rel_y_health = pix_y - HEALTH_DIGIT_Y;

    // Check if pixel is within each digit's boundaries
    wire in_digit0 = (pix_x >= DIGIT0_X) && (pix_x < DIGIT0_X + DIGIT_WIDTH) &&
                     (pix_y >= DIGIT_Y) && (pix_y < DIGIT_Y + DIGIT_HEIGHT);

    wire in_digit1 = (pix_x >= DIGIT1_X) && (pix_x < DIGIT1_X + DIGIT_WIDTH) &&
                     (pix_y >= DIGIT_Y) && (pix_y < DIGIT_Y + DIGIT_HEIGHT);

    wire in_digit2 = (pix_x >= DIGIT2_X) && (pix_x < DIGIT2_X + DIGIT_WIDTH) &&
                     (pix_y >= DIGIT_Y) && (pix_y < DIGIT_Y + DIGIT_HEIGHT);

    wire in_digit_health = (pix_x >= HEALTH_DIGIT_X) && (pix_x < HEALTH_DIGIT_X + DIGIT_WIDTH) &&
                           (pix_y >= HEALTH_DIGIT_Y) && (pix_y < HEALTH_DIGIT_Y + DIGIT_HEIGHT);

    // Apply the is_pixel_on function for each digit if the pixel is within
    assign seg0_on       = in_digit0       ? is_pixel_on(segments0, rel_x0, rel_y0)       : 1'b0;
    assign seg1_on       = in_digit1       ? is_pixel_on(segments1, rel_x1, rel_y1)       : 1'b0;
    assign seg2_on       = in_digit2       ? is_pixel_on(segments2, rel_x2, rel_y2)       : 1'b0;
    assign seg_health_on = in_digit_health ? is_pixel_on(segments_health, rel_x_health, rel_y_health) : 1'b0;

    // Combine the segment outputs to determine the final pixel state
    assign pixel_on = seg0_on | seg1_on | seg2_on | seg_health_on;

endmodule

Reference solution:
rtl/generated.v:     reg [15:0] rom_array[0:15];

    initial begin
      // Example placeholder bits for a 16×16 small alien
      rom_array[0]  = 16'h03C0;  
      rom_array[1]  = 16'h03C0;  
      rom_array[2]  = 16'h0FF0;  
      rom_array[3]  = 16'h0FF0;
      rom_array[4]  = 16'h3FFC;  
      rom_array[5]  = 16'h3FFC;
      rom_array[6]  = 16'hF3CF;  
      rom_array[7]  = 16'hF3CF;
      rom_array[8]  = 16'hFFFF;  
      rom_array[9]  = 16'hFFFF;
      rom_array[10] = 16'h0C30;
      rom_array[11] = 16'h0C30;
      rom_array[12] = 16'h300C;
      rom_array[13] = 16'h300C;
      rom_array[14] = 16'hC003;
      rom_array[15] = 16'hC003;
    end

    assign row_data = rom_array[row_index];