Canvas styles for demo

canvas-demo.css

.canvas-demo {
  --canvas-color: #f0f0f0;
  background-color: #212121;
  padding: 40px;
  border-radius: 4px;
  background-color: white;
  background-image: linear-gradient(45deg, var(--canvas-color) 25%, transparent 25%, transparent 75%, var(--canvas-color) 75%, var(--canvas-color)),
    linear-gradient(45deg, var(--canvas-color) 25%, transparent 25%, transparent 75%, var(--canvas-color) 75%, var(--canvas-color));
  background-size: 40px 40px;
  background-position: 0 0, 20px 20px;
  box-shadow: inset 0 0 2px #00000052;
}