Retro/Grade hitting PSN for $10 on Aug. 21

Retro/Grade, 24 Caret Games' music-based time-traveling reverse shooter, will be available for $9.99 by itself and for $14.99 bundled with its soundtrack, the developer announced today.

Its PlayStation Network-exclusive release had previously been confirmed for Aug. 21.

The studio also provided some details on how the game is played, since its core concept is a tough one to wrap your head around. Retro/Grade plays in reverse, and as protagonist Rick Rocket, you "un-fire" your shots while traveling backward through time along five discrete "lanes." In addition, you have to avoid enemy projectiles that are also being un-fired, since blocking their path with your ship would further screw up the space-time continuum — which you're trying to repair.

On a guitar controller, you tap the colored buttons to move between lanes, and strum to un-fire a shot. With a PlayStation 3 controller, up and down moves Rick's ship from lane to lane, and the X button un-fires. There's also a power-up that allows you to reverse the flow of time — that is, to make it travel forward — and it's activated with the whammy bar or circle button. "Retro/Grade is a rhythm game at its core," says 24 Caret co-founder Matt Gilgenbach. Confused? Check out the trailer below to see how it all plays out.

Retro/Grade's soundtrack of chiptune-esque electronic music, done by Skyler McGlothlin, will be sold separately on the PlayStation Store for $7.99, so buying the game/soundtrack bundle saves you $3. The game marks the beginning of Sony's "PlayStation Plus Presents" program, during which select indie games will be free for PlayStation Plus subscribers for eight weeks after launch.