Very cool concept, and the mechanics work very well. Some of the levels where you have to go in the opposite direction could be clearer on where exactly you have to stand although this being a trial and error game makes this not really a problem. I think that the life time of the replay character should last the same amount of time the player was alive for before pressing W because sometimes I would go onto a button wait a few seconds spawn a replay character and expect it to go onto the button then disappear consequently disabling the button but instead it just stays there. Anyway great game and fits the browser :)