Wait: so a flat ground is allowed?
Viewing post in Questions about the Game Jam
Yes it is, you can find it in the FAQ/Rules in this section:
- Use Only the Allowed Shapes: All visual elements (sprites, models, backgrounds, UI, characters, etc.) must be composed of only the revealed shapes. No custom or additional shapes are allowed. Exception: One flat ground plane or floor is permitted for gameplay purposes. Solid-colored or gradient backgrounds are also allowed.

