<canvas width='1000' height='800'></canvas>
<script>
    var tela = document.querySelector('canvas');
    var pincel = tela.getContext('2d');
    pincel.fillStyle="green";
    pincel.beginPath();
    pincel.fillRect(0,0,600,420);
    pincel.fillStyle='yellow';
    pincel.beginPath();
    pincel.moveTo(51,210);
    pincel.lineTo(300,51);
    pincel.lineTo(549,210);
    pincel.lineTo(300,369);
    pincel.lineTo(51,210);
    pincel.fill();
    pincel.fillStyle="darkblue";
    pincel.beginPath();
    pincel.arc(300,210,105,0,2*3.14);
    pincel.fill();
 
            