HTML5 Game - Rubber band with gravity

Description

Rubber band with gravity
Demo

<!doctype html>  
<html>  
 <head>  
  <meta charset="utf-8">  
  <title>Spring 5</title>  
  <style>canvas{border:1px solid red;}</style>  
 </head>  //from w w w. ja  va 2s .com
 <body>  
  <canvas id="canvas" width="400" height="400"></canvas>  
  <script>  
      class Ball {  
constructor() {
     this.radius = 4;
       
     this.x = 0;  
     this.y = 0;  
     this.vx = 0;  
     this.vy = 0;  
     this.rotation = 0;  
     this.scaleX = 1;  
     this.scaleY = 1;  
     this.color = "#ff0000";
     this.lineWidth = 1;  
   }  
     
   draw(context) {  
     context.save();  
     context.translate(this.x, this.y);  
     context.rotate(this.rotation);  
     context.scale(this.scaleX, this.scaleY);  
     context.lineWidth = this.lineWidth;  
     context.fillStyle = this.color;  
     context.beginPath();  
     context.arc(0, 0, this.radius, 0, (Math.PI * 2), true);  
     context.closePath();  
  context.fill();  
  if (this.lineWidth > 0) {  
    context.stroke();  
  }  
  context.restore();  
}
getBounds() {  
  return {  
    x: this.x - this.radius,  
    y: this.y - this.radius,  
    width: this.radius * 2,  
    height: this.radius * 2  
  };  
}

}  function captureMouse(element) {
  let mouse = {x: 0, y: 0, event: null},
      body_scrollLeft = document.body.scrollLeft,
      element_scrollLeft = document.documentElement.scrollLeft,
      body_scrollTop = document.body.scrollTop,
      element_scrollTop = document.documentElement.scrollTop,
      offsetLeft = element.offsetLeft,
      offsetTop = element.offsetTop;
  
  element.addEventListener('mousemove', function (event) {
    let x, y;
    
    if (event.pageX || event.pageY) {
      x = event.pageX;
      y = event.pageY;
    } else {
      x = event.clientX + body_scrollLeft + element_scrollLeft;
      y = event.clientY + body_scrollTop + element_scrollTop;
    }
    x -= offsetLeft;
    y -= offsetTop;
    
    mouse.x = x;
    mouse.y = y;
    mouse.event = event;
  }, false);
  
  return mouse;
} 
  window.onload = function () {  
    let canvas = document.getElementById('canvas'),  
        context = canvas.getContext('2d'),  
        mouse = captureMouse(canvas),  
        ball = new Ball(),  
        spring = 0.03,  
        friction = 0.9,  
        gravity = 0.5,  
        vx = 0,  
        vy = 0;  
  
    (function drawFrame () {  
      window.requestAnimationFrame(drawFrame, canvas);  
      context.clearRect(0, 0, canvas.width, canvas.height);  
  
      let dx = mouse.x - ball.x,  
          dy = mouse.y - ball.y,  
          ax = dx * spring,  
          ay = dy * spring;  
  
      vx += ax;  
      vy += ay;  
      vy += gravity;  
      vx *= friction;  
      vy *= friction;  
      ball.x += vx;  
      ball.y += vy;  
  
      context.beginPath();  
      context.moveTo(ball.x, ball.y);  
      context.lineTo(mouse.x, mouse.y);  
      context.stroke();  
      ball.draw(context);  
    }());  
  };  
  </script>  
 </body>  
</html>
HTML5 Game - Rubber band with gravity

Description

Demo

Related Topic
