Retro/Grade, finalist in the 2009 Independent Games Festival, has a demo out for PC users. It’s also coming to PS3, if that’s more your style.

But what is Retro/Grade? Well, let me build the concept for you. First, imagine a side-scrolling shooter, like R-Type or Jets’N'Guns. Now imagine that your movement is confined to a certain number of vertical flight channels, up to a maximum of five. Next, imagine that you’re playing the game in reverse. Oh, and it’s a rhythm game. To my knowledge, this is the only 2D shooter that you can play with a guitar controller.

That’s right! In Retro/Grade, you play as Rick Rocket, who has just saved the universe. But you did it so well that there’s an anomoly and you have to do it all again backwards. Using the standard PC controls, the arrow keys move your ship up and down between channels, and you press the space bar whenever your bullets (which, remember, are moving left because this is backwards) hit your ship’s gun. Enemy bullets move right back towards the ships that fired them, so you have to dodge those while connecting with your bullets to make sure that you don’t create a time paradox by not firing them. Each time you successfully fire your laser, an enemy ship appears on the right side of the screen as you un-destroy it.

I know, I know. It’s pretty hard to think about. My advice is to simply visit the site, watch the trailer, download the demo, (also available on Steam) and have a spectacular time with this little gem that’s already receiving a great deal of critical acclaim.