<canvas width="600" height="400"></canvas>
<script>
var tela = document.querySelector('canvas');
var pincel = tela.getContext('2d');
pincel.fillStyle = 'lightgray';
pincel.fillRect(0, 0, 600, 400);
function desenhaCirculo(x, y, raio, cor) {
pincel.fillStyle = cor;
pincel.beginPath();
pincel.arc(x, y, raio, 0, 2*3.14);
pincel.fill();
}
desenhaCirculo(300,200, 20, 'red')
desenhaCirculo(340,200, 20, 'black')
desenhaCirculo(300,240, 20, 'blue')
desenhaCirculo(260,200, 20, 'orange')
desenhaCirculo(300,160, 20, 'yellow')
</script>
