A great game, but I would change the ability of the enemies to pick up the code from the ones already killed in the same wave. Because sometimes the waves last so long, that the first enemies that appeared only die near the entrance/exit, and then the last enemy of that same wave comes in and grabs the code right when it enters the field. So maybe change that so the code can only be picked up by the next wave.
 "Sierra 7"){kind=icon}
 "Love"){kind=icon}
 "Ghost Hacker"){kind=icon}
 "Shield Defense"){kind=icon}
 "P.O.D."){kind=icon}