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
`timescale 1ns / 1ps

module tt_um_no_time_for_squares_tommythorn
  (input  wire [7:0] ui_in,    // Dedicated inputs
   output wire [7:0] uo_out,   // Dedicated outputs
   input  wire [7:0] uio_in,   // IOs: Input path -- UNUSED in this design.
   output wire [7:0] uio_out,  // IOs: Output path
   output wire [7:0] uio_oe,   // IOs: Enable path (active high: 0=input, 1=output)
   input  wire       ena,      // will go high when the design is enabled
   input  wire       clk,      // clock
   input  wire       rst_n     // reset_n - low to reset
   );

   // use bidirectionals as outputs
   assign uio_oe = 8'b11111111;

   wire       hour_button   = ui_in[7];
   wire       minute_button = ui_in[6];
   wire [3:0] debug_sel     = ui_in[3:0];

   wire       vga_hs;
   wire       vga_vs;
   wire [5:0] vga_rgb;

    // https://tinytapeout.com/specs/pinouts/#common-peripherals
   assign uo_out[0] = vga_rgb[5];
   assign uo_out[1] = vga_rgb[3];
   assign uo_out[2] = vga_rgb[1];
   assign uo_out[3] = vga_vs;
   assign uo_out[4] = vga_rgb[4];
   assign uo_out[5] = vga_rgb[2];
   assign uo_out[6] = vga_rgb[0];
   assign uo_out[7] = vga_hs;

   clock clock_inst(clk, !rst_n,
                    hour_button, minute_button, debug_sel,
                    vga_hs, vga_vs, vga_rgb,
                    uio_out);
endmodule


`default_nettype none
`timescale 1ns / 1ps

module clock(input wire        clock,
             input wire        reset,
             input wire        hour_button,
             input wire        minute_button,
             input wire [3:0]  debug_sel,

             output wire       vga_hs,
             output wire       vga_vs,
             output reg [5:0]  vga_rgb,
             output wire [7:0] debug_out);

   wire                       vga_visible;
   wire                       vga_horizontal_blank_strobe; // one clock wide pulse pr line
   wire                       vga_vertical_blank_strobe; // one clock wide pulse pr frame

   wire [9:0]      x, y;

   vga vga_inst(.clock(clock),
                .reset(reset),
                .vga_visible(vga_visible),
                .vga_horizontal_blank_strobe(vga_horizontal_blank_strobe),
                .vga_vertical_blank_strobe(vga_vertical_blank_strobe),
                .vga_hs(vga_hs),
                .vga_vs(vga_vs),
                .vga_x(x),
                .vga_y(y));

   reg                        vga_vertical_blank_strobe_delay;

   wire [1:0] command =
              (y == 500-1 && x == 800) ? 1 : // restart
	      x == 800 ? 2 : // stepy
	      vga_visible ? 3 : // stepx
	      0;

   reg [6:0]  frameno;
   reg [5:0]  second, minute;
   reg [3:0]  hour;

   wire hour_hit, min_hit, sec_hit;
   // XXX This limits it to 1 Hz
   wire advance_minute = frameno == 75 && minute_button;
   wire advance_hour   = frameno == 75 && hour_button;

   assign debug_out
     = debug_sel==0 ? frameno :
       debug_sel==1 ? {second,vga_horizontal_blank_strobe,vga_horizontal_blank_strobe} :
       debug_sel==2 ? {minute, 2'd 0} :
       {hour, 2'd 0};


   reg [53:0] sec_a, sec_b, sec_c;
   reg [53:0] min_a, min_b, min_c;
   reg [53:0] hour_a, hour_b, hour_c;

   // This is normally bad style; we pass through illegal state for up
   // to four cycles.  This is done on purpose for better timing (to
   // avoid a long nested conditional) and the illegal values will
   // never be observed
   always @(posedge clock) begin
      vga_vertical_blank_strobe_delay <= vga_vertical_blank_strobe;

      if (vga_vertical_blank_strobe) begin
         frameno <= frameno + 1;
      end
      if (frameno == 75) begin
         frameno <= 0;
         second <= second + 1;
      end
      if (second == 60) begin
         second <= 0;
      end
      if (second == 60 || advance_minute) begin
         minute <= minute + 1;
      end
      if (minute == 60) begin
         minute <= 0;
      end
      if (minute == 60 || advance_hour) begin
         hour <= hour + 1;
      end
      if (hour == 12) begin
         hour <= 0;
      end

      if (reset) begin
         hour <= 9;
         minute <= 26;
         second <= 18;
         frameno <= 0;
      end
   end // always @ (posedge clock)

   // Brute force; we can do better if we get time
   always @(posedge clock)
     if (vga_vertical_blank_strobe) begin // avoid glitching
	case (second)
          0: {sec_a, sec_b, sec_c} <= {54'hea00003ff16, 54'h3fffe80003, 54'h2db77016392477};
          1: {sec_a, sec_b, sec_c} <= {54'he800007ff17, 54'h1afffefffeb, 54'h2c7be00d8d3981};
          2: {sec_a, sec_b, sec_c} <= {54'he400007ff1b, 54'h33fffefffd2, 54'h2b59100d8d4bb3};
          3: {sec_a, sec_b, sec_c} <= {54'hde0000bff20, 54'h4affff3ffba, 54'h2a6dc004d95bfa};
          4: {sec_a, sec_b, sec_c} <= {54'hd50000bff29, 54'h61ffff3ffa3, 54'h29cc8004d96618};
          5: {sec_a, sec_b, sec_c} <= {54'hc90000fff34, 54'h77fffefff8e, 54'h297d50037d6c9e};
          6: {sec_a, sec_b, sec_c} <= {54'hbb00013ff41, 54'h8bffff3ff79, 54'h2961cffac1704c};
          7: {sec_a, sec_b, sec_c} <= {54'hac00013ff50, 54'h9effff3ff66, 54'h29758ffac16f20};
          8: {sec_a, sec_b, sec_c} <= {54'h9a00013ff62, 54'hb0ffff3ff54, 54'h29d40ffac16938};
          9: {sec_a, sec_b, sec_c} <= {54'h8700013ff75, 54'hbfffff3ff45, 54'h2a72cffac15f3c};
          10: {sec_a, sec_b, sec_c} <= {54'h7200017ff89, 54'hccffff7ff37, 54'h2b4feff1fd53d5};
          11: {sec_a, sec_b, sec_c} <= {54'h5d00013ff9f, 54'hd7ffffbff2b, 54'h2c458ff35942e8};
          12: {sec_a, sec_b, sec_c} <= {54'h4600013ffb6, 54'he0ffffbff22, 54'h2d8daff3592e5c};
          13: {sec_a, sec_b, sec_c} <= {54'h2e00017ffcd, 54'he5fffffff1c, 54'h2f223fea8d17e1};
          14: {sec_a, sec_b, sec_c} <= {54'h1500017ffe6, 54'he9fffffff18, 54'h30de1fea8cfc1e};
          15: {sec_a, sec_b, sec_c} <= {54'h3fffe00017fffd, 54'hea00007ff15, 54'h328fafe30ce2d7};
          16: {sec_a, sec_b, sec_c} <= {54'h3ffe6000140015, 54'he800007ff17, 54'h3491efe30cc2c1};
          17: {sec_a, sec_b, sec_c} <= {54'h3ffcd00014002e, 54'he400007ff1b, 54'h36c61fe30c9f83};
          18: {sec_a, sec_b, sec_c} <= {54'h3ffb6000100046, 54'hde0000bff20, 54'h38e1cfe4587cda};
          19: {sec_a, sec_b, sec_c} <= {54'h3ff9f00010005d, 54'hd50000bff29, 54'h3b388fe4585778};
          20: {sec_a, sec_b, sec_c} <= {54'h3ff89000140072, 54'hc90000fff34, 54'h3daf5fdb7c337e};
          21: {sec_a, sec_b, sec_c} <= {54'h3ff75000100087, 54'hbb00013ff41, 54'h9cfdcc00d4c};
          22: {sec_a, sec_b, sec_c} <= {54'h3ff6200010009a, 54'hac00013ff50, 54'h26b8fdcc3e740};
          23: {sec_a, sec_b, sec_c} <= {54'h3ff500001000ac, 54'h9a00013ff62, 54'h4e60fdcc3bf98};
          24: {sec_a, sec_b, sec_c} <= {54'h3ff410001000bb, 54'h8700013ff75, 54'h732cfdcc39abc};
          25: {sec_a, sec_b, sec_c} <= {54'h3ff340000c00c9, 54'h7200017ff89, 54'h96defddff76f5};
          26: {sec_a, sec_b, sec_c} <= {54'h3ff290000800d5, 54'h5d00013ff9f, 54'hb7b8fe6db52a8};
          27: {sec_a, sec_b, sec_c} <= {54'h3ff200000800de, 54'h4600013ffb6, 54'hd8bafe6db319c};
          28: {sec_a, sec_b, sec_c} <= {54'h3ff1b0000400e4, 54'h2e00017ffcd, 54'hf573fe80f1531};
          29: {sec_a, sec_b, sec_c} <= {54'h3ff170000400e8, 54'h1500017ffe6, 54'h11221fe80ef87e};
          30: {sec_a, sec_b, sec_c} <= {54'h3ff16ffffc00eb, 54'h3fffe00017fffd, 54'h1283aff20edfd7};
          31: {sec_a, sec_b, sec_c} <= {54'h3ff18ffffc00e9, 54'h3ffe6000140015, 54'h13c7eff20ecba1};
          32: {sec_a, sec_b, sec_c} <= {54'h3ff1cffffc00e5, 54'h3ffcd00014002e, 54'h14f31ff20eb8f3};
          33: {sec_a, sec_b, sec_c} <= {54'h3ff22ffff800e0, 54'h3ffb6000100046, 54'h15c9cffadaa8ba};
          34: {sec_a, sec_b, sec_c} <= {54'h3ff2bffff800d7, 54'h3ff9f00010005d, 54'h16728ffada9e38};
          35: {sec_a, sec_b, sec_c} <= {54'h3ff37ffff400cc, 54'h3ff89000140072, 54'h16d75ffbfe98de};
          36: {sec_a, sec_b, sec_c} <= {54'h3ff45ffff000bf, 54'h3ff75000100087, 54'h16e3c004c295ac};
          37: {sec_a, sec_b, sec_c} <= {54'h3ff54ffff000b0, 54'h3ff6200010009a, 54'h16d98004c29660};
          38: {sec_a, sec_b, sec_c} <= {54'h3ff66ffff0009e, 54'h3ff500001000ac, 54'h16840004c29bb8};
          39: {sec_a, sec_b, sec_c} <= {54'h3ff79ffff0008b, 54'h3ff410001000bb, 54'h15ecc004c2a51c};
          40: {sec_a, sec_b, sec_c} <= {54'h3ff8efffec0077, 54'h3ff340000c00c9, 54'h1507e00d7eb175};
          41: {sec_a, sec_b, sec_c} <= {54'h3ffa3ffff00061, 54'h3ff290000800d5, 54'h13ff800c5ac108};
          42: {sec_a, sec_b, sec_c} <= {54'h3ffbaffff0004a, 54'h3ff200000800de, 54'h12bda00c5ad51c};
          43: {sec_a, sec_b, sec_c} <= {54'h3ffd2fffec0033, 54'h3ff1b0000400e4, 54'h112830150eece1};
          44: {sec_a, sec_b, sec_c} <= {54'h3ffebfffec001a, 54'h3ff170000400e8, 54'hf7410150f081e};
          45: {sec_a, sec_b, sec_c} <= {54'h3fffe80003, 54'h3ff160000000ea, 54'hda6701dbb23a7};
          46: {sec_a, sec_b, sec_c} <= {54'h1afffefffeb, 54'h3ff18ffffc00e9, 54'hbb1e01c8f4261};
          47: {sec_a, sec_b, sec_c} <= {54'h33fffefffd2, 54'h3ff1cffffc00e5, 54'h986101c8f6523};
          48: {sec_a, sec_b, sec_c} <= {54'h4affff3ffba, 54'h3ff22ffff800e0, 54'h755c01b5b87da};
          49: {sec_a, sec_b, sec_c} <= {54'h61ffff3ffa3, 54'h3ff2bffff800d7, 54'h506801b5bacd8};
          50: {sec_a, sec_b, sec_c} <= {54'h77fffefff8e, 54'h3ff37ffff400cc, 54'h2a55023ffd1fe};
          51: {sec_a, sec_b, sec_c} <= {54'h8bffff3ff79, 54'h3ff45ffff000bf, 54'h3bc022c3f8ac};
          52: {sec_a, sec_b, sec_c} <= {54'h9effff3ff66, 54'h3ff54ffff000b0, 54'h3de38022c01e40};
          53: {sec_a, sec_b, sec_c} <= {54'hb0ffff3ff54, 54'h3ff66ffff0009e, 54'h3b720022c04558};
          54: {sec_a, sec_b, sec_c} <= {54'hbfffff3ff45, 54'h3ff79ffff0008b, 54'h392cc022c0699c};
          55: {sec_a, sec_b, sec_c} <= {54'hccffff7ff37, 54'h3ff8efffec0077, 54'h36e9e0217c8e55};
          56: {sec_a, sec_b, sec_c} <= {54'hd7ffffbff2b, 54'h3ffa3ffff00061, 54'h34c98018d8b148};
          57: {sec_a, sec_b, sec_c} <= {54'he0ffffbff22, 54'h3ffbaffff0004a, 54'h32bfa018d8d1dc};
          58: {sec_a, sec_b, sec_c} <= {54'he5fffffff1c, 54'h3ffd2fffec0033, 54'h30f330178cef91};
          59: {sec_a, sec_b, sec_c} <= {54'he9fffffff18, 54'h3ffebfffec001a, 54'h2f3010178d0bbe};
        endcase
        case (minute)
          0: {min_a, min_b, min_c} <= {54'h10100003feff, 54'h14fff600014, 54'h2be840a2814104};
          1: {min_a, min_b, min_c} <= {54'hfc00013ff00, 54'h2dfff6bfff9, 54'h2ac7f085e95823};
          2: {min_a, min_b, min_c} <= {54'hf600023ff02, 54'h48fff6bffde, 54'h29ae2072496f50};
          3: {min_a, min_b, min_c} <= {54'hed00037ff06, 54'h62fff6fffc3, 54'h28e6d055c5835d};
          4: {min_a, min_b, min_c} <= {54'he200043ff0e, 54'h7afff73ffaa, 54'h28550043219150};
          5: {min_a, min_b, min_c} <= {54'hd400053ff18, 54'h91fff7bff91, 54'h28175027a99c1d};
          6: {min_a, min_b, min_c} <= {54'hc30005fff26, 54'ha6fff87ff79, 54'h2829900ce5a0b5};
          7: {min_a, min_b, min_c} <= {54'hb10006fff34, 54'hbafff8fff63, 54'h28702ff205a428};
          8: {min_a, min_b, min_c} <= {54'h9d00077ff46, 54'hccfff97ff4f, 54'h28e78fe085a112};
          9: {min_a, min_b, min_c} <= {54'h870007fff5a, 54'hdafffa7ff3d, 54'h29c85fc6e59849};
          10: {min_a, min_b, min_c} <= {54'h6f0008bff6f, 54'he8fffb3ff2c, 54'h2adcdfad298e65};
          11: {min_a, min_b, min_c} <= {54'h5600093ff86, 54'hf2fffc3ff1e, 54'h2c3d0f94217e90};
          12: {min_a, min_b, min_c} <= {54'h3d00097ff9e, 54'hfafffcfff13, 54'h2db0df83c56b3d};
          13: {min_a, min_b, min_c} <= {54'h220009bffb8, 54'hfefffe3ff0a, 54'h2f950f6bc95282};
          14: {min_a, min_b, min_c} <= {54'h70009bffd3, 54'h100ffff3ff04, 54'h318d3f5c69362f};
          15: {min_a, min_b, min_c} <= {54'h3ffec000a3ffec, 54'h10100003feff, 54'h33a94f44811c74};
          16: {min_a, min_b, min_c} <= {54'h3ffd3000980007, 54'hfc00013ff00, 54'h35daff3e68f8d3};
          17: {min_a, min_b, min_c} <= {54'h3ffb8000980022, 54'hf600023ff02, 54'h38542f2fc8d590};
          18: {min_a, min_b, min_c} <= {54'h3ff9e00094003d, 54'hed00037ff06, 54'h3aeddf2244afcd};
          19: {min_a, min_b, min_c} <= {54'h3ff86000900056, 54'he200043ff0e, 54'h3d6d0f1c208990};
          20: {min_a, min_b, min_c} <= {54'h3ff6f00088006f, 54'hd400053ff18, 54'he5f172860cd};
          21: {min_a, min_b, min_c} <= {54'h3ff5a0007c0087, 54'hc30005fff26, 54'h2aa9f1a643545};
          22: {min_a, min_b, min_c} <= {54'h3ff4600074009d, 54'hb10006fff34, 54'h5532f16040cf8};
          23: {min_a, min_b, min_c} <= {54'h3ff340006c00b1, 54'h9d00077ff46, 54'h7dc8f1887e3c2};
          24: {min_a, min_b, min_c} <= {54'h3ff260005c00c3, 54'h870007fff5a, 54'ha395f2467b9d9};
          25: {min_a, min_b, min_c} <= {54'h3ff180005000d4, 54'h6f0008bff6f, 54'hcbfdf28ab9155};
          26: {min_a, min_b, min_c} <= {54'h3ff0e0004000e2, 54'h5600093ff86, 54'hf010f35236a10};
          27: {min_a, min_b, min_c} <= {54'h3ff060003400ed, 54'h3d00097ff9e, 54'h110fdf4047462d};
          28: {min_a, min_b, min_c} <= {54'h3ff020002000f6, 54'h220009bffb8, 54'h12f90f554b21e2};
          29: {min_a, min_b, min_c} <= {54'h3ff000001000fc, 54'h70009bffd3, 54'h14b03f68eb00df};
          30: {min_a, min_b, min_c} <= {54'h3ff00ffffc0101, 54'h3ffec0009fffed, 54'h16544f7ea6e227};
          31: {min_a, min_b, min_c} <= {54'h3ff04ffff00100, 54'h3ffd3000980007, 54'h176dff90eacb03};
          32: {min_a, min_b, min_c} <= {54'h3ff0afffe000fe, 54'h3ffb8000980022, 54'h188e2fa54ab490};
          33: {min_a, min_b, min_c} <= {54'h3ff13fffcc00fa, 54'h3ff9e00094003d, 54'h196adfc2469ffd};
          34: {min_a, min_b, min_c} <= {54'h3ff1efffc000f2, 54'h3ff86000900056, 54'h19f10fd5229310};
          35: {min_a, min_b, min_c} <= {54'h3ff2cfffb000e8, 54'h3ff6f00088006f, 54'h1a355ff0aa87fd};
          36: {min_a, min_b, min_c} <= {54'h3ff3dfffa400da, 54'h3ff5a0007c0087, 54'h1a15900a668295};
          37: {min_a, min_b, min_c} <= {54'h3ff4ffff9400cc, 54'h3ff4600074009d, 54'h19e42026867fc8};
          38: {min_a, min_b, min_c} <= {54'h3ff63fff8c00ba, 54'h3ff340006c00b1, 54'h19578038068432};
          39: {min_a, min_b, min_c} <= {54'h3ff79fff8400a6, 54'h3ff260005c00c3, 54'h186c5050668ba9};
          40: {min_a, min_b, min_c} <= {54'h3ff91fff780091, 54'h3ff180005000d4, 54'h1764d06b2a9665};
          41: {min_a, min_b, min_c} <= {54'h3ffaafff70007a, 54'h3ff0e0004000e2, 54'h1609008422a5d0};
          42: {min_a, min_b, min_c} <= {54'h3ffc3fff6c0062, 54'h3ff060003400ed, 54'h1484d09446b9dd};
          43: {min_a, min_b, min_c} <= {54'h3ffdefff680048, 54'h3ff020002000f6, 54'h12a900abcad142};
          44: {min_a, min_b, min_c} <= {54'h3fff9fff68002d, 54'h3ff000001000fc, 54'h10a530ba6aed2f};
          45: {min_a, min_b, min_c} <= {54'h14fff600014, 54'h3feff000000101, 54'hea740d4830894};
          46: {min_a, min_b, min_c} <= {54'h2dfff6bfff9, 54'h3ff04ffff00100, 54'hc5af0d86b2a53};
          48: {min_a, min_b, min_c} <= {54'h62fff6fffc3, 54'h3ff13fffcc00fa, 54'h763d0f5c7738d};
          49: {min_a, min_b, min_c} <= {54'h7afff73ffaa, 54'h3ff1efffc000f2, 54'h4d900fc239ad0};
          50: {min_a, min_b, min_c} <= {54'h91fff7bff91, 54'h3ff2cfffb000e8, 54'h23e51012bc34d};
          51: {min_a, min_b, min_c} <= {54'ha6fff87ff79, 54'h3ff3dfffa400da, 54'h3f9490fce7ee05};
          52: {min_a, min_b, min_c} <= {54'hbafff8fff63, 54'h3ff4ffff9400cc, 54'h3d0121028416f8};
          53: {min_a, min_b, min_c} <= {54'hccfff97ff4f, 54'h3ff63fff8c00ba, 54'h3a628100044182};
          54: {min_a, min_b, min_c} <= {54'hdafffa7ff3d, 54'h3ff79fff8400a6, 54'h37fb50f2e46a19};
          55: {min_a, min_b, min_c} <= {54'he8fffb3ff2c, 54'h3ff91fff780091, 54'h3581d0efa89375};
          56: {min_a, min_b, min_c} <= {54'hf2fffc3ff1e, 54'h3ffaafff70007a, 54'h334500e320ba50};
          57: {min_a, min_b, min_c} <= {54'hfafffcfff13, 54'h3ffc3fff6c0062, 54'h3125d0d7c4deed};
          58: {min_a, min_b, min_c} <= {54'hfefffe3ff0a, 54'h3ffdefff680048, 54'h2f4500c24901e2};
          59: {min_a, min_b, min_c} <= {54'h100ffff3ff04, 54'h3fff9fff68002d, 54'h2d8230ade9227f};
        endcase
        case (hour)
          0: {hour_a, hour_b, hour_c} <= {54'ha400003ff5c, 54'h14fff600014, 54'h32b800a280c580};
          1: {hour_a, hour_b, hour_c} <= {54'h8300053ff69, 54'h63fff7bffbf, 54'h30a8c027a904ac};
          2: {hour_a, hour_b, hour_c} <= {54'h400008bff9e, 54'h97fffb3ff7d, 54'h32d51fad290073};
          3: {hour_a, hour_b, hour_c} <= {54'h3ffec000a3ffec, 54'ha400003ff5c, 54'h38a80f4480be00};
          4: {hour_a, hour_b, hour_c} <= {54'h3ff9d000880041, 54'h8300053ff69, 54'hc0cf1728474c};
          5: {hour_a, hour_b, hour_c} <= {54'h3ff69000500083, 54'h410008bff9d, 54'h8accf28abc42c};
          6: {hour_a, hour_b, hour_c} <= {54'h3ff5dffffc00a4, 54'h3ffec0009fffed, 54'he9c0f7ea74f80};
          7: {hour_a, hour_b, hour_c} <= {54'h3ff7dfffb00097, 54'h3ff9d000880041, 54'h10bacff0ab114c};
          8: {hour_a, hour_b, hour_c} <= {54'h3ffc0fff780062, 54'h3ff69000500083, 54'he87106b2b15d3};
          9: {hour_a, hour_b, hour_c} <= {54'h14fff600014, 54'h3ff5c0000000a4, 54'h8c000d4835880};
          10: {hour_a, hour_b, hour_c} <= {54'h62fff7bffc0, 54'h3ff7dfffb00097, 54'hb731012bcd51};
          11: {hour_a, hour_b, hour_c} <= {54'h97fffb3ff7d, 54'h3ffc0fff780062, 54'h38a210efa85303};
        endcase
     end

   // Three precomputed triangles; XXX get edgeeqn integrated
   tile hour_tile(clock, hour_a, hour_b, hour_c, command, hour_hit);
   tile min_tile(clock, min_a, min_b, min_c, command, min_hit);
   tile sec_tile(clock, sec_a, sec_b, sec_c, command, sec_hit);

   always @(posedge clock) begin
      vga_rgb <= 6'b000000; // default black background

      if (sec_hit)
	vga_rgb <= 6'b111111; // white
      else if (hour_hit)
	vga_rgb <= 6'b110000; // red
      else if (min_hit)
	vga_rgb <= 6'b111100; // yellow

      // 12 hour/5 min markers
      if (x == 320 && y ==   0 || // 12
	  x == 440 && y ==  32 || //  1
	  x == 528 && y == 120 || //  2
          x == 560 && y == 240 || //  3
	  x == 528 && y == 360 || //  4
	  x == 440 && y == 448 || //  5
	  x == 320 && y == 560 || //  6
	  x == 200 && y == 448 || //  7
	  x == 112 && y == 360 || //  8
          x ==  80 && y == 240 || //  9
	  x == 112 && y == 120 || // 10
	  x == 200 && y ==  32    // 11
	  )
        vga_rgb <= 6'b111111; // white

      if (!vga_visible)
        vga_rgb <= 0;
   end
endmodule


`ifdef SIMCLOCK
module tb;
   reg clock = 1;
   reg reset = 1;
   wire [5:0] vga_rgb;
   wire [7:0] debug_out;

   wire       hour_button = 0;
   wire       minute_button = 0;
   wire [3:0] debug_sel = 0;

   wire       vga_hs, vga_vs;
   wire       vga_visible, vga_vertical_visible, vga_horizontal_visible;
   wire       vga_horizontal_blank_strobe, vga_vertical_blank_strobe;

   always #5 clock = ~clock;

   clock clock_inst(clock,
                    reset,
                    hour_button,
                    minute_button,
                    debug_sel,

                    vga_hs,
                    vga_vs,
                    vga_rgb,
                    debug_out);

   initial begin
      $dumpfile("clock.vcd");
      $dumpvars(0, clock_inst);
      #20 reset = 0;
      #100000000 $finish;
   end
endmodule
`endif


`default_nettype none
`timescale 1ns / 1ps

// https://www.mythtv.org/wiki/Modeline_Database#VESA_ModePool
// 640 	480 	75 Hz 	37.5 kHz 	ModeLine "640x480" 31.50 640 656 720 840 480 481 484 500 -HSync -VSync

// The implementation of the VGA timing signals is very naive, but
// this way is easy to understand and immediately relatable to the
// ModeLine parameters.
//
// Pixels are visible if vga_visible
// vga_horizontal_blank_strobe marks the beginning of the horizontal blanking
// vga_vertical_blank_strobe marks the beginning of the vertical blanking
module vga(input  wire      clock,
           input wire       reset,
           output wire      vga_visible,
           output reg       vga_horizontal_blank_strobe, // one clock wide pulse pr line
           output reg       vga_vertical_blank_strobe, // one clock wide pulse pr frame
           output reg       vga_hs,
           output reg       vga_vs,
           output reg [9:0] vga_x,
           output reg [9:0] vga_y );
// >>> Module Implementation Begin

// <<< Module Implementation End
endmodule




`ifdef SIMVGA
module tb;
   reg clock = 1;
   reg reset = 1;
   wire hour_button;
   wire minute_button;
   wire [3:0] debug_sel;

   wire       vga_hs;
   wire       vga_vs;
   wire [7:0] debug_out;

   wire       vga_visible, vga_vertical_visible, vga_horizontal_visible;
   wire       vga_horizontal_blank_strobe, vga_vertical_blank_strobe;

   always #5 clock = ~clock;

   vga vga_inst(.clock(clock),
                .reset(reset),
                .vga_visible(vga_visible),
                .vga_horizontal_blank_strobe(vga_horizontal_blank_strobe),
                .vga_vertical_blank_strobe(vga_vertical_blank_strobe),
                .vga_hs(vga_hs),
                .vga_vs(vga_vs));

   initial begin
      $dumpfile("vga.vcd");
      $dumpvars(0, vga_inst);
      #20 reset = 0;
      #10000000 $finish;
   end
endmodule
`endif


`default_nettype none
`timescale 1ns / 1ps

// Basic "Render me a triangle" render
// Every clock one of three things can happen:
// - restart
// - stepy
// - stepx
// Only the latter produces a pixel

`define W 18

// NB: this design should end up with just a three 18b adders and 6
// 18b registers, but we should probably change the design to do this
// explicitly.
//
// NB: Note that we should be able to tell of many x-steps are executed
// and thus precompute B' = B - x-steps * A, thus replacing the y-step
// with just e <= e + B' and eliminate e0, save half the registers.
//
// A more delicate change would be to reduce the precision from 18b
// down to ~ 10b, but that's likely to introduce a bunch of edge
// cases.
module tile(input wire clock,
	    // Render equation parameters; changing them should be followed by a restart
	    input wire [`W*3-1:0] a, // That's actually three signed 18-bit values
	    input wire [`W*3-1:0] b,
	    input wire [`W*3-1:0] c,

	    input wire [1:0]  command, // 0 nop, 1 restart, 2 stepy, 3 stepx

	    output wire	      inside_triangle);

   reg [`W*3-1:0]	      e0, e; // 18*3*2 = 108 bit

   assign inside_triangle = !(e[`W-1] | e[`W*2-1] | e[`W*3-1]); // If all values in e are positive

   always @(posedge clock)
     if (command == 1) begin
	e0 <= c;
	e <= c;
     end else if (command == 2) begin
	// CSE works, right?
	e0 <= {e0[`W*3-1:`W*2] + b[`W*3-1:`W*2], e0[`W*2-1:`W] + b[`W*2-1:`W], e0[`W-1:0] + b[`W-1:0]};
	e <= {e0[`W*3-1:`W*2] + b[`W*3-1:`W*2], e0[`W*2-1:`W] + b[`W*2-1:`W], e0[`W-1:0] + b[`W-1:0]};
     end else if (command == 3) begin
	e <= {e[`W*3-1:`W*2] + a[`W*3-1:`W*2], e[`W*2-1:`W] + a[`W*2-1:`W], e[`W-1:0] + a[`W-1:0]};
     end
endmodule


`ifdef SIM
// FINE!  I'll simulate this

module tb;
   reg clock = 1;
   always #5 clock = 1 - clock;

   reg [1:0] command = 0;
   wire      hour_hit;

   tile hour_tile(clock, 54'h3ff7dfffb00097, 54'h3ff9d000880041, 54'h10bacff0ab114c, command, hour_hit);
   initial begin
      $monitor(clock, command, hour_hit);

      #10 command = 1;
      @(posedge clock);
      command = 0;

      #10 command = 3;
      @(posedge clock);
      @(posedge clock);
      @(posedge clock);
      @(posedge clock);
      command = 0;
      #100 $finish;
   end
endmodule
`endif


Reference solution:
rtl/generated.v: 
   parameter      M1 = 10 'd 640;
   parameter      M2 = 10 'd 656;
   parameter      M3 = 10 'd 720;
   parameter      M4 = 10 'd 840;
   parameter      M5 = 10 'd 480;
   parameter      M6 = 10 'd 481;
   parameter      M7 = 10 'd 484;
   parameter      M8 = 10 'd 500;
   parameter      hs_active = 1'd 0; // negative sync
   parameter      vs_active = 1'd 0;

   reg            vga_horizontal_visible, vga_vertical_visible;
   assign vga_visible = vga_horizontal_visible & vga_vertical_visible;

   always @(posedge clock) begin
      vga_vertical_blank_strobe <= 0;
      vga_horizontal_blank_strobe <= 0;

      vga_x <= vga_x + 1;

      if (vga_x == M1-1) begin
         vga_horizontal_blank_strobe <= 1;
         vga_horizontal_visible <= 0;
      end

      if (vga_x == M2-1)
        vga_hs <= hs_active;

      if (vga_x == M3-1)
        vga_hs <= !hs_active;

      if (vga_x == M4-1) begin
         vga_horizontal_visible <= 1;
         vga_x <= 0;
         vga_y <= vga_y + 1;

         if (vga_y == M5-1) begin
            vga_vertical_blank_strobe <= 1;
            vga_vertical_visible <= 0;
         end

         if (vga_y == M6-1)
           vga_vs <= vs_active;

         if (vga_y == M7-1)
           vga_vs <= !vs_active;

         if (vga_y == M8-1) begin
            vga_y <= 0;
            vga_vertical_visible <= 1;
         end
      end

      if (reset) begin
         vga_x <= 0;
         vga_y <= 0;
         vga_hs <= !hs_active;
         vga_vs <= !hs_active;
         vga_vertical_visible <= 1;
         vga_horizontal_visible <= 1;
         vga_vertical_blank_strobe <= 0;
         vga_horizontal_blank_strobe <= 0;
      end
   end