Additional exercises – Sharpening the axe

1. Oh no! We added collisions to the boulders and inner walls of the arena, but not to the outer walls. Add a StaticBody2D that stops the player from escaping the arena.
2. Create a base scene for the boulders, inherit two boulders from that, and make their shapes different. Also, make sure you update the collision shape so that the player collides correctly with them.