The paint follows your cursor. Click on the mouse to stamp some paint. Left and Right Arrow Keys change the color of the paint while the Up and Down Arrow Keys change the size of the paint. Press the S Key to swap between a circle and a square (Shape of Paint) Press the eraser to erase EVERYTHING... except the code of course!
v1.1 I fixed a bug where it was almost impossible to switch the paint shape. Just so you know, the eraser gets blocked by the paint so just restart the game to erase. Seeing amazing sandboxes made by other people inspired me to make my own. Updates may include more features (e.g. extra shapes, more UI, smoother feel).