hm, I guess because there are no real projectiles.
its more like you shoot, then the engine create in distance x a "hit box trigger" for enemies.
enemy in zone = dead... not in trigger zone show impact on the ground
with 2D games its easier, you create your bullet which has a path, if a enemy hit the bullet on the path... destroy...
but its fun to create some top down worlds
maybe it will end in a complete game...
Old school FPS fan, DOOM!!! Why GG not working on my AMIGA 500?