Interesting concept! I played only as a single player. The challenge of remembering which keys did what was unique, however once you get one "player" to have more than one movement control key the gimmick loses its charm, since you can just ignore the 2nd player. Quite a novel idea. I had some issues seeing what was where, since the room basically only zooms out once only one player is active and the controls hovering above each player are quite dark.
I had no issues with lag or performance. Tutorial level would have been nice, and more of a scoring system or progression of some kind would improve replayability.