Nice. I especially like the switchable game-modes, that change the gameplay speed or alter the formations, in which the enemies appear. That switching-mode is a good idea. A simultaneous two-player mode would also be nice, by the way. Or a 4-player mode for 4-player-adapters, that would also be cool. There aren't all that many C64 games so far, that make use of those adapters, so any good new 4-player game would be welcome.