Draw! Press S to open settings. Press E to toggle pen/eraser. Hold C or press the green flag to clear the canvas. Pen mode: 0 only uses arrow keys, 1 uses arrow keys or mouse to move the pen.
I made this a few months ago to try out the pen as I'd never really used it much before. I never finished it, but decided to share my progress anyways. The eraser just draws over stuff the same color as the background, so if you change the color of the background after erasing something, you'll see the eraser marks. All code by me. The pencil in the thumbnail is from the scratch library, and all other art is by me.