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}

ES5 Canvas Thing

  1. var canvas = document.body.appendChild(
  2.   document.createElement('canvas')
  3. ),
  4. c = canvas.getContext("2d"),
  5. size = canvas.width,
  6. quarterSize = size / 4,
  7. eightSize = size / 8,
  8. halfSize = size / 2,
  9. TWO_PI = Math.PI * 2,
  10. bombNum = 3,
  11. bombs = [],
  12. wanderers = {}, 
  13. wandererIndex = 0,
  14. particles = {},
  15. particleIndex = 0;
  16.  
  17. canvas.width = canvas.height = 300
  18.  
  19. c.fillStyle = "rgb(100,100,100)";
  20. c.fillRect(0,0,size,size);
  21.  
  22. function Particle(x, y){
  23.   this.x = x;
  24.   this.y = y;
  25.   var rad = 3 + Math.random() * 6;
  26.   var theta = Math.random() * TWO_PI;
  27.   this.vx = rad * Math.cos(theta);
  28.   this.vy = rad * Math.sin(theta);
  29.   this.alpha = 1;
  30.   particleIndex++;
  31.   this.index = particleIndex;
  32.   particles[this.index] = this;
  33. }
  34. Particle.prototype.draw = function(){
  35.   this.x += this.vx;
  36.   this.y += this.vy;
  37.   this.vx *= 0.9;
  38.   this.vy *= 0.9;
  39.   this.alpha -= 0.05;
  40.  
  41.   if (this.alpha <= 0){
  42.     this.alpha = 0;
  43.     delete particles[this.index];
  44.  
  45.   }
  46.  
  47.   c.fillStyle = "rgba(255,255,255,"+this.alpha+")";
  48.   c.beginPath();
  49.   c.arc(this.x, this.y, 1, 0, TWO_PI, false);
  50.   c.fill();
  51. };
  52.  
  53. function Bomb(){
  54.   this.x = quarterSize + Math.random() * halfSize;
  55.   this.y = quarterSize + Math.random() * halfSize;
  56.   this.radius = 15 + Math.random() * 20;
  57. }
  58. Bomb.prototype.draw = function(){
  59.   c.fillStyle = "#e64c25";
  60.   c.beginPath();
  61.   c.arc(this.x, this.y, this.radius, 0, TWO_PI, false);
  62.   c.fill();
  63. };
  64.  
  65. function Wanderer(x, y){
  66.   this.x = x;
  67.   this.y = y;
  68.   this.vx = Math.random() * 4 - 2;
  69.   this.vy = Math.random() * 4 - 2;
  70.   particleIndex++;
  71.   this.index = particleIndex;
  72.   particles[this.index] = this;
  73. }
  74. Wanderer.prototype.die = function(){
  75.   for (var j = 0; j < 4; j++){
  76.     new Particle(this.x, this.y);
  77.   }
  78.  
  79.   delete particles[this.index];
  80. };
  81. Wanderer.prototype.draw = function(){
  82.   this.x += this.vx;
  83.   this.y += this.vy;
  84.  
  85.   if (Math.random() < 0.1){
  86.     this.vx = Math.random() * 4 - 2;
  87.     this.vy = Math.random() * 4 - 2;
  88.   }
  89.  
  90.   if (this.x < 0) this.x = size;
  91.   if (this.x > size) this.x = 0;
  92.   if (this.y < 0) this.y = size;
  93.   if (this.y > size) this.y = 0;
  94.  
  95.   c.fillStyle = "white";
  96.   c.beginPath();
  97.   c.arc(this.x, this.y, 2, 0, TWO_PI, false);
  98.   c.closePath();
  99.   c.fill();
  100.  
  101.   for (var i = 0; i < bombNum; i++){
  102.     var bomb = bombs[i];
  103.     var dx = this.x - bomb.x;
  104.     var dy = this.y - bomb.y;
  105.     if (Math.sqrt(dx * dx + dy * dy) < bomb.radius){
  106.       this.die();
  107.     }
  108.   }
  109. };
  110.  
  111. for (var i = 0; i < bombNum; i++){
  112.   bombs[i] = new Bomb();
  113. }
  114.  
  115. new Wanderer(eightSize, eightSize); 
  116.  
  117. setInterval(function(){
  118.   c.fillStyle = "rgba(100,100,100, 0.2)";
  119.   c.fillRect(0,0,size,size);
  120.   c.strokeStyle = "white";
  121.   c.beginPath();
  122.   c.arc(eightSize, eightSize, 5, 0, TWO_PI, false);
  123.   c.stroke();
  124.  
  125.   if (Math.random() < 0.02){
  126.     new Wanderer(eightSize, eightSize); 
  127.   }
  128.  
  129.   for (var i = 0; i < bombNum; i++){
  130.     bombs[i].draw();
  131.   }
  132.  
  133.   for (var i in wanderers){
  134.     wanderers[i].draw(); 
  135.   }
  136.  
  137.   for (var i in particles){
  138.     particles[i].draw();
  139.   }
  140. }, 16);

An old es5 speedcoded thing…

snippet.zone ~ 2021-22 /// {s/z}