Wow, this is polished to a sheen. Sound design is on point, sfx are perfect and the loop's a bopper. The visuals are great too - good choice of palette, awesome sprite work in general, and the UI's tidy and clear. I played around with strategy a bit but in general it seems hard to lose, especially if you just launch each drone as soon as it's available. Still, the amount of time you've got to defeat the invader feels just right. Short enough to give a real sense of urgency, but enough to safely stave off the threat.
Only thing that breaks my heart is that George Clinton would be out here trying to conquer galaxies.