click the color squares to change the color of your pen, click the trash can to delete everything on screen (it will ask you before deleting it), click the canvases to change the background color, click the lines at the bottom to change the thickness of your brush/eraser. also ↑ ↑ ↓ ↓ ← → ← →BA.
Thank you @LGlobe for some help with the code, also thanks MSpaint for the inspiration