canvas_draw_background.js

function draw_background()
{
  // First we erase everything on the canvas:
  canvas.clearRect(0, 0, canvas_element.width, canvas_element.height);
  // And then we change the color of our "paintbrush":
  canvas.fillStyle = "#1EBA00";
  // And then we draw a colored rectangle that covers the entire canvas:
  canvas.fillRect(0, 0, canvas_element.width, canvas_element.height);
}