The controls are very odd, to say the least. Running requires you to build momentum before you get any sort of speed, and if you run in any direction and let go of it mid-run, you stop dead in your tracks... but if you hold the opposite direction while running and let go of the first, your momentum carries over into a slide.

The aim on the portal gun is also not just inaccurate (shooting in the same place without moving the mouse creates three 'portal points' in different places each time), but there are instances where I managed to shoot through a wall and get to the exit in much quicker time... which, for some reason, killed me despite there being no turret or wall blocking me.

Also, is there a reason the second room of every test chamber is askew by, like, 10%? It seems like the rooms are shifted just a bit to the right, and it's really disorienting at times.a