All depends on what part of the game you consider: Level geometry is indeed 2D (or rather 2D projectable without intersection, hence the 2.5D moniker) Gamepla

All depends on what part of the game you consider: Level geometry is indeed 2D (or rather 2D projectable without intersection, hence the 2.5D moniker) Gameplay though, is 3D, and actually hampered by not being able to look up down, which for shooting was compensated by vertical auto-aim. There are many places where it's hard to see the enemies above or below, or even where you're going to go/navigate. Luckily the level design is usually nicely done and usually caters for that with enough room space to kinda see things and/or elevators but there are a couple of areas that can be especially tricky or frustrating.