HTML5 Game - Springing in two dimensions

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  2. HTML5 Game
  3. Canvas Animation
  4. Spring

Description

Springing in two dimensions

Demo

ResultView the demo in separate window 

<!doctype html>  
    <html>  
     <head>  
      <style>canvas{border:1px solid red;}</style>  
     </head>  
     <body>  
      <canvas id="canvas" width="400" height="400"></canvas>  
      <script>  
class Ball {  //from   w ww.j ava 2  s. c o m
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  
  };  
}

}  
      window.onload = function () {  
        let canvas = document.getElementById('canvas'),  
            context = canvas.getContext('2d'),  
            ball = new Ball(),  
            spring = 0.03,  
            friction = 0.95,  
            targetX = canvas.width / 2,  
            targetY = canvas.height / 2,  
            vx = 0,  
            vy = 0;  
      
        (function drawFrame () {  
          window.requestAnimationFrame(drawFrame, canvas);  
          context.clearRect(0, 0, canvas.width, canvas.height);  
      
          let dx = targetX - ball.x,  
              dy = targetY - ball.y,  
              ax = dx * spring,  
              ay = dy * spring;  
      
          vx += ax;  
          vy += ay;  
          vx *= friction;  
          vy *= friction;  
          ball.x += vx;  
          ball.y += vy;  
          ball.draw(context);  
        }());  
      };  
      </script>  
     </body>  
    </html>

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