Create a stamp using Canvas 2d.
Stamp meaning only responding to the mousedown, mouseup, or click events in the browser.
Think of stamp as a design limitation. How can you make something interesting if the user can only click in different places? Can you do something with the order of their clicks? Is it different if they click on the top half of the screen versus the bottom half? What if they click in exactly the same place more than once without moving the mouse?