Atum is a free 3D game about someone playing a 2D game
Mixes 2D platforming with first-person pointing-and-clicking.
IGF 2013 entry Atum is a game that lets you be in two places at once... sort of. The idea is that you're locked into a first-person perspective where you're sitting at a computer playing a 2D platformer.
The WASD keys control your 2D game-within-a-game avatar, while your mouse looks around a white, sterile Mirror's Edge-esque room where you can pick up objects that manipulate the 2D game. Can't get through security lasers? Light up some cigarettes in the "real world" (i.e. the 3D world) and watch the smoke drown out the game-within-a-game's beams. Need to move some metal boxes? Pick up a magnet and hold it next to the relevant part of the screen.
Developer Team Cupcake - a group of third year students at the Netherlands' NHTV Breda University - noted Atum was inspired by such sci-fi classics as Blade Runner and Philip K. Dick's Martian Time Slip. There are plenty of heady philosophical allusions in the game too, with books like The Unbearable Lightness of Being scattered throughout the environment.
The puzzles themselves aren't that mind-bending, though, and the controls can be a little unwieldy, but it's still a unique concept that's worth a look-see. Check it out here.