Pew pew pew! Ha, I love how the simplest concepts make for the most addictive gameplay.
This game is as basic as it gets: on a blank, featureless playing field, squares fly at you from off-screen and you have to fend them off with mouse-controlled rapid fire, and dodge them with the WASD keys. Add to that some satisfying sound effects and explosions, tight controls, and a freaking leaderboard, and I'm hooked.
The cool thing about this pure dodge-and-shoot experience is that there's a point where you kind of "become one" with the game, your reflexes go sky high and you dodge some really hard square patterns with ease. This state doesn't last forever, obviously, and it is prone to ending abruptly if something reminds you of the real world surrounding you, but it is epic while it lasts.
Only reason I'm not giving it a 5 is that it's, like, paper thin in content and context. Still pretty awesome, though.