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HTML

              
                
<!DOCTYPE html>
<html>
  <head>
    <meta charset="utf-8">
    <title>Bouncing balls</title>
    <link rel="stylesheet" href="style.css">
  </head>

  <body>
    <h1>bouncing balls</h1>
    <p>Ball count: </p>
    <canvas></canvas>

    <script src="main-finished.js"></script>
  </body>
</html>
              
            
!

CSS

              
                html, body {
  margin: 0;
}

html {
  font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif;
  height: 100%;
}

body {
  overflow: hidden;
  height: inherit;
}

h1 {
  font-size: 2rem;
  letter-spacing: -1px;
  position: absolute;
  margin: 0;
  top: -4px;
  right: 5px;

  color: transparent;
  text-shadow: 0 0 4px white;
}
p {
  position: absolute;
  margin: 0;
  top: 35px;
  right: 5px;
  color: #aaa;
}

              
            
!

JS

              
                // define variable for ball count paragraph

const para = document.querySelector('p');
let count = 0;

// setup canvas
const canvas = document.querySelector('canvas');
const ctx = canvas.getContext('2d');

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

// funcion que genera un numero random
function random(min, max) {
  const num = Math.floor(Math.random() * (max - min + 1)) + min;
  return num;
}

//Constructor Shape(forma)
function Shape(x,y,velX,velY,exists){
  this.x = x;
  this.y = y;
  this.velX = velX;
  this.velY = velY;
  this.exists = exists;
}

//Creo el constructor Ball (pelotas) del constructor Shape(forma) + size + color
function Ball(x, y, velX, velY,exists, color, size){
  Shape.call(this, x, y, velX, velY, exists );
  this.color = color;
  this.size = size;
 }
/*👉*/Ball.prototype = Object.create(Shape.prototype);
//El nuevo objeto (Ball) tiene Shape.prototype como prototipo del constructor Ball y, por lo tanto, heredará, si es necesario, todos los métodos(funciones) disponibles en Shape.prototype. y no solo el constructor.

Ball.prototype.constructor = Ball;
//Sin esto el constructor Ball me devolveria el constructor Shape en vez de devolverme el constructor Ball-/*👈*/


//Al constructor Ball le agrego la function Ball(pelotas)
Ball.prototype.draw = function() {
  ctx.beginPath();
  ctx.fillStyle = this.color;
  ctx.arc(this.x, this.y, this.size, 0, 2 * Math.PI);
  ctx.fill();
};

//Al constructor Ball le agrego la funcion update(actualizar)
Ball.prototype.update = function() {
  if((this.x + this.size) >= width) {
    this.velX = -(this.velX);
  }

  if((this.x - this.size) <= 0) {
    this.velX = -(this.velX);
  }

  if((this.y + this.size) >= height) {
    this.velY = -(this.velY);
  }

  if((this.y - this.size) <= 0) {
    this.velY = -(this.velY);
  }

  this.x += this.velX;
  this.y += this.velY;
};

//Al constructor Ball le agrego la funcion collisionDetect(detector de colicion)
Ball.prototype.collisionDetect = function() {
  for (let j = 0; j < balls.length; j++) {
    if (!(this === balls[j]) && balls[j].exists) {
      const dx = this.x - balls[j].x;
      const dy = this.y - balls[j].y;
      const distance = Math.sqrt(dx * dx + dy * dy);

      if (distance < this.size + balls[j].size) {
        balls[j].color = this.color = 'rgb(' + random(0, 255) + ',' + random(0, 255) + ',' + random(0, 255) +')';
      }
    }
  }
};






//Creo el constructor EvilCircle(circulo malvado) del constructor Shape
function EvilCircle(x,y,velX,vely,exists,color,size){
  Shape.call(this,x,y,20,20,exists);
  this.color='white';
  this.size=10;
}
/*👉*/EvilCircle.prototype = Object.create(Shape.prototype);
EvilCircle.prototype.constructor = EvilCircle;/*👈*/

//Al constructor EvilCircle le agrego la funcion draw(dibujo)
EvilCircle.prototype.draw = function() {
  ctx.beginPath();
  ctx.lineWidth=3;
  ctx.strokeStyle = this.color;
  ctx.arc(this.x, this.y, this.size, 0, 2 * Math.PI);
  ctx.stroke();
};


//Al constructor EvilCircle le agrego la function checkBounds(comprobacion de límites)
EvilCircle.prototype.checkBounds = function() {
  if((this.x + this.size) >= width) {
    this.velX = -(this.velX);
  }

  if((this.x - this.size) <= 0) {
    this.velX = -(this.velX);
  }

  if((this.y + this.size) >= height) {
    this.velY = -(this.velY);
  }

  if((this.y - this.size) <= 0) {
    this.velY = -(this.velY);
  }

  
};

//Al constructor EvilCilrcle le agrego la function setControl(establecer el control)
EvilCircle.prototype.setControl=function(){
  let _this = this;
window.onkeydown = function(e) {
    if (e.key === 'a') {
      _this.x -= _this.velX;
    } else if (e.key === 'd') {
      _this.x += _this.velX;
    } else if (e.key === 'w') {
      _this.y -= _this.velY;
    } else if (e.key === 's') {
      _this.y += _this.velY;
    }
  };

};


//Al constructor EvilCircle le agrego la function collisionDetect(detector de colicion)
EvilCircle.prototype.collisionDetect = function() {
  for (let j = 0; j < balls.length; j++) {
    if (balls[j].exists) {
      const dx = this.x - balls[j].x;
      const dy = this.y - balls[j].y;
      const distance = Math.sqrt(dx * dx + dy * dy);

      if (distance < this.size + balls[j].size) {
        balls[j].exists = false;        
        count--;
        para.textContent = 'Ball count: ' + count;
      }
    }
  }
}

// Definir matriz para almacenar bolas y poblarla
const balls = [];

while(balls.length < 25) {
  const size = random(10,20);
  let ball = new Ball(
    // ball position always drawn at least one ball width
    // away from the adge of the canvas, to avoid drawing errors
    random(0 + size,width - size),
    random(0 + size,height - size),
    random(-7,7),
    random(-7,7),
    true,
    'rgb(' + random(0,255) + ',' + random(0,255) + ',' + random(0,255) +')',
    size
  );
  balls.push(ball);
  count++;
  para.textContent = 'Ball count: ' + count;
}

//Defini el bucle que sigue dibujando la escena constantemente
let evil = new EvilCircle(random(0,width), random(0,height), true);
evil.setControl();

function loop() {
  ctx.fillStyle = 'rgba(0,0,0,0.25)';
  ctx.fillRect(0,0,width,height);

  for(let i = 0; i < balls.length; i++) {
    if(balls[i].exists) {
      balls[i].draw();
      balls[i].update();
      balls[i].collisionDetect();
    }
  }

  evil.draw();
  evil.checkBounds();
  evil.collisionDetect();

  requestAnimationFrame(loop);
}



loop();
              
            
!
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