convert this code into a 2d drawing plane. make simple schematics editor with snapable properre grid. make some menu at top to set grid size in units and dimension in px em etc...: <!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>drawacube</title>
    <style>
        canvas {
            display: block;
            margin: auto;
        }
    </style>
</head>
<body>
    <canvas id="canvas"></canvas>
  <script>
const canvas = document.getElementById("canvas");
const ctx = canvas.getContext("2d");

canvas.width = window.innerWidth;
canvas.height = window.innerHeight;

const rotationSpeed = 0.1;
const gridSize = 50;
const gridSpacing = 25;
const zoomStep = 10;
const minZoom = 100;
const maxZoom = 2000;
const centerFocus = 100;

let grid = [];
for (let x = -gridSize; x <= gridSize; x += gridSpacing) {
for (let y = -gridSize; y <= gridSize; y += gridSpacing) {
for (let z = -gridSize; z <= gridSize; z += gridSpacing) {
grid.push({ x, y, z });
}
}
}

let lastClickedPoint = null;
const clickedPoints = [];
let angleX = 95.03;
let angleY = 119.99;
let zoom = 100;
let dragStart = null;

let offset = {
x: gridSpacing / 25,
y: gridSpacing / 25,
z: 0
};

function rotate(point, angleX, angleY) {
const { x, y, z } = point;

let centeredX = x - offset.x;
let centeredY = y - offset.y;
let centeredZ = z - offset.z;

const cosX = Math.cos(angleX);
const sinX = Math.sin(angleX);
const cosY = Math.cos(angleY);
const sinY = Math.sin(angleY);

const newY = centeredY * cosX - centeredZ * sinX;
const newZ = centeredY * sinX + centeredZ * cosX;
const newX = centeredX * cosY - newZ * sinY;
const newZ2 = centeredX * sinY + newZ * cosY;

return {
x: newX + offset.x,
y: newY + offset.y,
z: newZ2 + offset.z
};
}


function project(point, width, height) {
const { x, y, z } = point;

const scale = zoom / (centerFocus + z);
const newX = x * scale + width / 2;
const newY = y * scale + height / 2;

return { x: newX, y: newY, scale };
}

function findClosestPoint(point) {
const threshold = 20;
let minDist = Infinity;
let minIndex = -1;

for (let i = 0; i < grid.length; i++) {
const projected = project(rotate(grid[i], angleX, angleY), canvas.width, canvas.height);
const dx = point.x - projected.x;
const dy = point.y - projected.y;
const dist = Math.sqrt(dx * dx + dy * dy);

if (dist < minDist && dist <= threshold) {
minDist = dist;
minIndex = i;
}
}

return minIndex !== -1 ? grid[minIndex] : null;
}

let mouseDown = false;
let activeLine = null;
const lines = [];

canvas.addEventListener("wheel", (e) => {
e.preventDefault();
zoom += e.deltaY * -0.1 * zoomStep;
zoom = Math.min(Math.max(zoom, minZoom), maxZoom); // Limit zoom to min and max thresholds
});

canvas.addEventListener("mousedown", (e) => {
dragStart = { x: e.clientX, y: e.clientY };
});

canvas.addEventListener("mousemove", (e) => {
if (dragStart) {
const deltaX = e.clientX - dragStart.x;
const deltaY = e.clientY - dragStart.y;
angleX += deltaY * 0.01;
angleY += deltaX * 0.01;
dragStart = { x: e.clientX, y: e.clientY };
}
});

canvas.addEventListener("mouseup", (e) => {
mouseDown = false;
dragStart = null;
if (activeLine !== null) {
const canvasRect = canvas.getBoundingClientRect();
const mouseX = e.clientX - canvasRect.left;
const mouseY = e.clientY - canvasRect.top;
const endPoint = findClosestPoint({ x: mouseX, y: mouseY });

if (endPoint !== activeLine[activeLine.length - 1]) {
activeLine.push(endPoint);
lines.push(activeLine);
}
activeLine = null;
}

if (lastClickedPoint !== null) {
const canvasRect = canvas.getBoundingClientRect();
const mouseX = e.clientX - canvasRect.left;
const mouseY = e.clientY - canvasRect.top;
const clickedPoint = findClosestPoint({ x: mouseX, y: mouseY });

if (clickedPoint !== null) {
if (lastClickedPoint === clickedPoint) {
lastClickedPoint = null;
} else {
lines.push([lastClickedPoint, clickedPoint]);
clickedPoints.push(clickedPoint);
lastClickedPoint = null;
}
}
} else {
const canvasRect = canvas.getBoundingClientRect();
const mouseX = e.clientX - canvasRect.left;
const mouseY = e.clientY - canvasRect.top;
const clickedPoint = findClosestPoint({ x: mouseX, y: mouseY });

if (clickedPoint !== null) {
lastClickedPoint = clickedPoint;
clickedPoints.push(clickedPoint);
}
}
});
function drawLine(line) {
ctx.beginPath();

for (let i = 0; i < line.length - 1; i++) {
const projectedStart = project(rotate(line[i], angleX, angleY), canvas.width, canvas.height);
const projectedEnd = project(rotate(line[i + 1], angleX, angleY), canvas.width, canvas.height);

ctx.moveTo(projectedStart.x, projectedStart.y);
ctx.lineTo(projectedEnd.x, projectedEnd.y);
}

ctx.strokeStyle = "rgba(25,200,25,0.2)";
ctx.lineWidth = 2;
ctx.stroke();
}

function calculateGridCenter(grid) {
let totalX = 0;
let totalY = 0;
let totalZ = 0;
const pointsCount = grid.length;

for (const point of grid) {
totalX += point.x;
totalY += point.y;
totalZ += point.z;
}

return {
x: totalX / pointsCount,
y: totalY / pointsCount,
z: totalZ / pointsCount,
};
}

function draw() {
ctx.fillStyle = "rgba(1,2,1,0.8)";
ctx.fillRect(0, 0, canvas.width, canvas.height);

for (const point of grid) {
const rotated = rotate(point, angleX, angleY);
const projected = project(rotated, canvas.width, canvas.height);

ctx.beginPath();
if (projected.scale > 0) {
ctx.arc(projected.x, projected.y, 2 * projected.scale, 0, Math.PI * 2);
ctx.closePath();
const gradient = ctx.createRadialGradient(projected.x, projected.y, 0, projected.x, projected.y, 2 * projected.scale);
gradient.addColorStop(0, "rgba(255,155,255,0.5)");
gradient.addColorStop(0.5, "rgba(55,255,25,0.8)");
gradient.addColorStop(1, "rgba(55,25,255,0.2)");
ctx.fillStyle = gradient;
ctx.fill();
}
}

// Drawing clicked points in green
ctx.fillStyle = "rgba(255,200,50,0.5)";
for (const clickedPoint of clickedPoints) {
const rotated = rotate(clickedPoint, angleX, angleY);
const projected = project(rotated, canvas.width, canvas.height);

ctx.beginPath();
if (projected.scale > 0) {
ctx.arc(projected.x, projected.y, 4 * projected.scale, 0, Math.PI * 2);
ctx.closePath();
ctx.fill();
}
}

for (const line of lines) {
drawLine(line);
}

if (activeLine !== null) {
drawLine(activeLine);
}

angleX += rotationSpeed;
angleY += 0;

requestAnimationFrame(draw);
}


draw();
  </script>
    </body>
</html>