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Some Boxes

  1. const canvas = document.createElement('canvas'),
  2.   c = canvas.getContext('2d');
  3.  
  4. document.body.appendChild(canvas);
  5. document.body.style.margin = 0;
  6.  
  7. function resize() {
  8.   canvas.width = innerWidth;
  9.   canvas.height = innerHeight;
  10.   c.fillStyle = '#ccc';
  11.   c.fillRect(0, 0, canvas.width, canvas.height);
  12. }
  13. resize();
  14. addEventListener('resize', resize);
  15.  
  16. const cols = ['#555', 'white', 'gray', '#a4c3eb', '#75879e'];
  17.  
  18. const getCol = () => cols[Math.floor(Math.random() * cols.length)];
  19.  
  20. function rect() {
  21.   let x = Math.random() * innerWidth;
  22.   let y = Math.random() * innerHeight;
  23.   let dx = x;
  24.   let dy = y;
  25.   let size = Math.min(innerWidth, innerHeight);
  26.   let width = size * Math.random() * Math.random() + 30;
  27.   let height = size * Math.random() * Math.random() + 30;
  28.   let halfWidth = width / 2;
  29.   let halfHeight = height / 2;
  30.   let col = getCol();
  31.   let damp = 5 + Math.random() * 70;
  32.   let alpha = 0.2 + Math.random() * 0.4;
  33.  
  34.   function move() {
  35.     if (Math.random() < 0.5) {
  36.       dy = y;
  37.       dx += Math.random() * Math.random() * size - size / 2;
  38.     } else {
  39.       dx = x;
  40.       dy += Math.random() * Math.random() * size - size / 2;
  41.     }
  42.   }
  43.  
  44.   return () => {
  45.     if (Math.random() < 0.01) {
  46.       move();
  47.     }
  48.  
  49.     if (x < halfWidth) {
  50.       dx = innerWidth - width;
  51.     }
  52.  
  53.     if (y < halfHeight) {
  54.       dy = innerHeight - height;
  55.     }
  56.  
  57.     if (x > innerWidth + halfWidth) {
  58.       dx = width;
  59.     }
  60.  
  61.     if (y > innerHeight + halfHeight) {
  62.       dy = height;
  63.     }
  64.  
  65.     x += (dx - x) / damp;
  66.     y += (dy - y) / damp;
  67.  
  68.     c.globalAlpha = alpha;
  69.     c.fillStyle = col;
  70.     c.fillRect(x - halfWidth, y - halfHeight, width, height);
  71.   };
  72. }
  73.  
  74. let rects = [];
  75. let NUM = 30;
  76. for (let i = 0; i < NUM; i++) {
  77.   rects.push(rect());
  78. }
  79.  
  80. function loop() {
  81.   c.globalCompositeOperation = 'source-over';
  82.   c.globalAlpha = 0.01;
  83.   c.fillStyle = '#ccc';
  84.   c.fillRect(0, 0, canvas.width, canvas.height);
  85.  
  86.   c.globalCompositeOperation = 'hard-light';
  87.   for (let i = 0; i < NUM; i++) {
  88.     rects[i]();
  89.   }
  90.   requestAnimationFrame(loop);
  91. }
  92. loop();
snippet.zone ~ 2021-22 /// {s/z}