This is a fun take on the typical wave shooter, and encapsulates the theme very well. I think the core conceit is very strong, as I've come to expect from you, and you've executed on it very well.
I do have a handful of things I would tweak, though:
- The level feels quite small from the start, even before platforms start disappearing. I imagine the intent was to keep rounds shorter/tighter, but it makes the whole thing feel quite claustrophobic at times, especially when paired with the slippery player controls. Neither of those things individually are necessarily bad, but the combination of the two definitely led to some frustration.
- The visual clarity between the intact tiles and broken ones was a little difficult to parse, especially in the heat of an intense round. There were a lot of times I would be artificially restricting what tiles I moved on because the lowest levels of decay can be very difficult to distinguish from the goop. Either a different (brighter) tile color or a different way of having the tiles break would have cleared it up.
- The enemy spawning locations could make it really tricky to actually reclaim ground at times. Oftentimes I would already be trapped on one edge/corner and all of the enemies would spawn clustered around that area which doesn't help in the long term. Maybe some amount of weight on the random spawns would improve things? They could probably also spawn slightly closer to the edge of the screen in general, the arrows showing up so far before they could be interacted with struck me as odd.
That looks like kind of a lot of negative, but it really is just nitpicking, I loved a lot about it too!
- It's a very satisfying gameplay loop, and an excellent use of the theme. It's very compelling to go back and try for another high score.
- I do quite like the absurdist framing of the plot, and I appreciate that you have that opening cutscene to give some clarity, crude as it may be. It definitely has a certain amount of charm.
- The different spray patterns were a great way to add some subtle strategy to a largely quite simple game, and they force you to really think about your best option to kill any given enemy.
- Tracking your highscore between rounds is a nice touch!
I can truly see so many more ideas that could effortlessly slot into this existing formula, which I think is how you know an arcade game has succeeded. You make a lot of similar games for jams, but it's because you know what you're doing and it works! I'll never stop telling you to refine your graphics though X)