↑A Slower Speed of Light is a first-person game prototype in which players navigate a 3D space while picking up orbs that reduce the speed of light in increments. Custom-built, open-source relativistic graphics code allows the speed of light in the game to approach the player’s own maximum walking speed. Visual effects of special relativity gradually become apparent to the player, increasing the challenge of gameplay. These effects, rendered in realtime to vertex accuracy, include the Doppler effect (red- and blue-shifting of visible light, and the shifting of infrared and ultraviolet light into the visible spectrum); the searchlight effect (increased brightness in the direction of travel); time dilation (differences in the perceived passage of time from the player and the outside world); Lorentz transformation (warping of space at near-light speeds); and the runtime effect (the ability to see objects as they were in the past, due to the travel time of light). Players can choose to share their mastery and experience of the game through Twitter. A Slower Speed of Light combines accessible gameplay and a fantasy setting with theoretical and computational physics research to deliver an engaging and pedagogically rich experience.

And if we are already at it: ↑Dream of Pixels—↑the prototype of which you can play for free in your browser—completely reverses time in the Tetris universe:

Dream of Pixels is a beautiful falling blocks puzzle game, in reverse. The brilliant twist on the old classic is the unpacking of tetromino blocks in place of the usual packing. Simply tap on the descending grid to unpack the tetrominos and watch them spin, rotate and drop with gravity. Clear the lines from the beautiful cloudy grid fast enough or it’s—dream over.