PSP-Hacks.com

Description:
DAVEX's modified version of Akop's SMSPlusPSP -- the SEGA Master System & Game Gear emulator. This unofficial version features both DAVEX's rewind and mirror mods.

...With rewind you can warp back in time, within the game, without worrying about saving states. If you made a mistake, you can press "rewind" button and undo it....

...In mirror mode, like it's name says, all graphics are horizontally inverted. So, if your favorite platform game is played from left to right, this time you can have the choice of playing it from right to left...