Just use your mouse to draw. rectangles. Hover over the arrow in the bottom right corner to show the undo and redo buttons. If you see any bugs, please tell me.
UPDATES: (MM / DD / YY) 5/24/22: Hopefully fixed a bug that I found on mobile and fixed the bug that sometimes caused the undo and redo to come up slightly before or after the box 5/22/22: Added undo and redo 5/11/2022: Initial Release Thanks to @imfh for reminding me how to do the bobbing up and down thing that is used for the arrow. Otherwise, just me.
