<canvas width="600" height="400"></canvas>
<script>
var tela = document.querySelector("canvas");
var pincel = tela.getContext("2d");
//Quadrado
pincel.fillStyle = "green";
pincel.fillRect(0, 0, 600, 400);
//Losango
pincel.fillStyle = "yellow";
pincel.beginPath();
pincel.moveTo(300, 40);
pincel.lineTo(40, 200);
pincel.lineTo(300, 360);
pincel.lineTo(560, 200);
pincel.fill();
//Circulo
pincel.fillStyle = "blue";
pincel.beginPath();
pincel.arc(300, 200, 100, 0, 2*3.14);
pincel.fill();
</script>
