       <li>
                    <code>fillRect</code>: to create a filled rectangle. 4
                    arguments: <code>x</code>, <code>y</code>,
                    <code>width</code> and <code>height</code>.
                  </li>
                  <br />
                  <li><code>strokeRect</code>: to draw just the outline</li>
                  <br />
                  <li>
                    <code>clearRect</code>: to clear all the pixel under this
                    rectangle
                