All levels unlocked.
Despite what they say, in short bursts war can be exceptionally fun. For proof, check out Matthew Hydman's 10 Second War, a unique little topdown puzzle shooter game with a time-bending main mechanic. You play as a little squad of soldiers tasked with eliminating the opposing turrets and bots, but you only have ten seconds to get the job done. Fortunately, you get to select each unit individually and control them with the [WASD] keys and your mouse through the ten second span, and then hit [F] to "finish" the unit. Then you can do it all again with the next guy, creating a tiny little ballet of violence as your previous soldiers go about their choreography. A robust level editor gives the game some great replayability but be warned: you might find yourself playing each level ten or tweny times trying to perfect each shot and dodge for maximum efficiency.