We're glad you enjoyed it! The theme's connection is the fact that what you'd usually see in a menu (Credits, mute option, pause) are ALL inside the game, including start game, reset and quit game. So shooting enemies isn't just... for shooting. It's to protect you, change difficulty, for strategy, to get health, to pause the game, to start the game... And if you don't use the WASD keys to move, you can ALSO shoot enemies to move!
That's what we meant with "nearly omni-purpose design", and that's how it fits the "dual-purpose design" theme, at least in our conception. But thank you for the feedback - it means we didn't make it as clear as possible in-game!