When I say the phrase "online multiplayer" visions of tea-bagging and PvP probably fill your head. They don't apply here though, as you are playing against opponents across a temporal divide -- not just a physical one. This is indeed a multiplayer game, but instead of duking it out in real-time you face an echo of their playthrough. You know, their ghost. This asynchronous multiplayer brings out some interesting playstyles, and is fun to see in action. The game's tagline is awesome enough that I'll reproduce it here: "So the guy I'm fighting is actually a recording - a recording of a fight against a recording of a fight, all the way back to the beginning of time?"
The controls are simple, given that you have the same move and shoot verbs you possess in every shmup since forever. When you blast an enemy they drop health and a weapon, which have either horizontal or vertical firing patterns. As you progress more and more enemies appear on the screen -- eventually you become overwhelmed and die. So far so tame, right? The cool part is that you aren't shooting mindless drones with repetitive AI, you have that pesky human element to deal with. Your enemies are all recordings of previous playthroughs of other players, and when you die your recording joins their ranks.
In my playing I came across a bunch of playstyles emerge from the game's basic framework. I saw white hat players that refused to fire and simply buzzed about the stage. I fought some malicious buggers that jetted about the screen erratically and sent out a constant stream of bullets; I quickly shot down bumbling enemies foolish enough to stand still. After a while I saw a character that shared my initials that zoomed across the stage and shot me down. My past self from ten minutes ago went and blew me up -- I ended up acting out a time travel paradox.
In time the number of enemies piles up and blends together into a cacophony of bullets. Since the enjoyment comes from the character study element it's a shame the endgame is a bullet hell, but as long as there are fewer than a dozen enemies it's an interesting time. Oh, and if some asshole named DAS zaps you, you know who to thank.
N.B. You'll need the Unity webplayer to play, but if you wish to support Mr. Buckenham or want a touch of absurdity you can purchase a downloadable version that gives you the option to replace the ships with dogs' heads.