ball.js

const canvas = document.getElementById("ballCanvas");
const ctx = canvas.getContext("2d");
let raf;
let running = false;

const ball = {
  x: 100,
  y: 100,
  vx: 5,
  vy: 1,
  radius: 12,
  color: "blue",
  draw() {
    ctx.beginPath();
    ctx.arc(this.x, this.y, this.radius, 0, Math.PI * 2, true);
    ctx.closePath();
    ctx.fillStyle = this.color;
    ctx.fill();
  },
};

function clear() {
  ctx.fillStyle = "rgba(255, 255, 255, 0.3)";
  ctx.fillRect(0, 0, canvas.width, canvas.height);
}

function draw() {
  clear();
  ball.draw();
  ball.x += ball.vx;
  ball.y += ball.vy;

  if (ball.y + ball.vy > canvas.height || ball.y + ball.vy < 0) {
    ball.vy = -ball.vy;
  }
  if (ball.x + ball.vx > canvas.width || ball.x + ball.vx < 0) {
    ball.vx = -ball.vx;
  }

  raf = window.requestAnimationFrame(draw);
}

canvas.addEventListener("mousemove", (e) => {
  if (!running) {
    clear();
    ball.x = e.clientX;
    ball.y = e.clientY;
    ball.draw();
  }
});

canvas.addEventListener("click", (e) => {
  if (!running) {
    raf = window.requestAnimationFrame(draw);
    running = true;
  }
});

canvas.addEventListener("mouseout", (e) => {
  window.cancelAnimationFrame(raf);
  running = false;
});

ball.draw();