Q.U.B.E. is a clever first-person puzzle game that tells the story of an unnamed protagonist trapped inside a maze, equipped with a pair of gloves that allows him to extrude or contract multi-coloured cubes by willpower alone. Manipulating the cubes is as simple as targeting them before pressing the left or right mouse button, although cubes will stop responding to your commands when they have reached the limit of their extension or contraction capabilities.
No tutorial sequence is included with the game, but it really doesn't take more than a minute to learn the controls and start solving puzzles in every room. You can't save your progress though, so be prepared to spend about an hour or so if you're planning to beat Q.U.B.E. in one sitting.