<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
</head>
<body>
<canvas width="600" height="400"></canvas>
<script>
const lienzo = document.querySelector('canvas');
const pincel = lienzo.getContext('2d');
let x=0;
let z=1;
pincel.fillStyle = 'gray';
pincel.fillRect(0,0, 600,400);
setInterval(actualizaPantalla,100);
function limpiarlienzo(){
pincel.clearRect(0,0,600,400);
}
function crearCirculo(x,y,radio){
pincel.fillStyle = 'blue';
pincel.beginPath();
pincel.arc(x,y,radio,0,2*Math.PI);
pincel.fill();
}
function actualizaPantalla(){
limpiarlienzo();
crearCirculo(x,20,10);
if(x==580){
z=0;
}
if(x==0){
z=1;
}
if(z==1){
x=x+20
}else{
x=x-20
}
}
</script>
</body>
</html>