Topware's swarm-based tower defense variant, Planets Under Attack, looks sort of perfect. It sees various brightly coloured planets orbiting in off-kilter star systems, and unloading huge torrents of space-fleets each other. Vaguely reminiscent of Eufloria, I suppose, only where that was a subtle ambient tune, this is more like a gilded pop torrent.
Observe the trailer below.
It's "coming soon", apparently.