<canvas></canvas>

/* Center the demo */
html, body { height: 100%; }
body {
  display: flex;
  justify-content: center;
  align-items: center;
}

body {
  background-color: #333;
}

var canvas = document.querySelector('canvas');
var ctx = canvas.getContext('2d');
ctx.fillStyle = '#0074d9';
ctx.fillRect(0, 0, 100, 100);