It's when you kill a galaxy, I guess, or maybe when you kill a fancy, elaborate party
Galacide can seem like a complex combination of mechanics, and in some ways, it is. But to me, the culminations of its eclectic parts form very simple praises and complaints.
The puzzle mode, which could be a pretty cool aesthetic twist on standard color-matching puzzles, becomes annoying when you factor in Galacide's mechanic of changing a block's color (instead of adding a new block with a new color). The standalone puzzle mode was clearly not the game's main production goal, and it just doesn't feel compatible with its mechanics.
Puzzle-intensive sections of the campaign are actually made more fun by this block-changing mechanic, as it allows blocks to be grouped densely in the map, and makes navigating through said blocks quite thrilling. However, Galacide has a bad habit of being stingy with the exact color of block you need to get through these obstacles, so the random number generator can really make or break your survival.
The pure-schmup sections of the campaign benefit from a cool weapon-level mechanic, such that your weapon gains experience as you move quickly through the level; encouraging you to take out enemies fast and charge ahead. But this fun comes to a stop pretty rapidly when block obstacles start crowding the level, and slowness causes the weapon to level down -- making enemies even more annoying to deal with than the blocks already made them. (Shades of God Hand, here.)
And while the schmup action is typically pretty easy, difficulty ramps up dramatically in a few boss fights. Having a bullet-hell thrown at you, by surprise, at the very end of a level, is ... unpleasant.
Galacide has some briefly-thrilling highs, and some briefly-irritatating lows. But ultimately, since the campaign is a mere 7 levels, brevity overrides whatever highs or lows you might encounter. Unless you're super-into the game, in which case the endless mode provides you with a way to compete for high scores, ... like pretty much any other schmup.
Better than: Syder Arcade
Not as good as: Sine Mora
Hard to say: if Galacide could be made more viable with further polish, or would always feel this haphazard.
Progress: Didn't quite beat the final boss.