<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, 220, 10, 'yellow');
desenhaCirculo(300, 200, 10, 'black');
desenhaCirculo(300, 180, 10, 'yellow');
desenhaCirculo(280, 200, 10, 'yellow');
desenhaCirculo(320, 200, 10, 'yellow');
</script>
