Flashback is basically a scrolling platformer, but if you play it for a bit you'll realise that its a bit more involved. You can jump and hold onto ledges, draw and put back your weapon, crouch and roll. This is a kind of puzzle game because most screens need to be solved and you have to figure out how to kill people loosing the least amount of energy possible. This is an ok game but I didn't think it was fantastic. It just happens to resemble the name of the site ;).You can download Windows start up screens related to this game on the Startup Screens page.
