Fixed the on-hit particle effects

The on-hit particles were actually already implemented, but the upgrade from godot3 to godot4 reset all the settings and I had to reconfigure them. Now they're actually visible again and I think they are extremely satisfying. It's true though that the hitbox of the enemies seems too small.

Simplified the enemies

In the original version, the enemies wear down and get smaller as they take damage. This is built into the design of the sprite so it's like they're shedding layers. This I think is probably too visually complex and the final result is this little red square that'll look way too muddy in the final game I think. So I simplified them into single stage enemies with less health

Added health and a pseudo-death

Enemies now do not collide with the player, but will dive-bomb into them and do damage as they die themselves. The player then “dies”… In reality I just make them invisible but it's enough to emulate the real behaviour for when I really design a death screen