Sand monolith

I'm at my dad's house for one week so I decided to make at least 5 games in that time period.

The fourth game is about drawing in the sand.

Source code :  https://www.puzzlescript.net/play.html?p=b09554ec2968bfa3bf45c247d2654228

Controls : - Arrow keys to move - X to select - Z to undo, R to restart