This game is pretty neat. Great job with completing your game!
The sense of progression in this game feels really good. That's a challenge in a normal game, let alone a jam game where you want players to get to the good stuff quickly, but not so fast that your game is over too fast. You've found the perfect balance. The art is what is is, charming in its MS-paint-esque glory. The little grunts and sound effects, too. It all adds up to feel almost like an old flash game, which is awesome.
I think it could use a bit more polish in places, like hit boxes and maybe making healing/health more valuable. There were a few times when I tried to absorb a building but my reach actually hit a nearby tree instead. And health didn't seem as useful because more damage meant you wouldn't lose health in the first place. That's a classic games problem though. Maybe it'd be more interesting if attackers could damage your overtaken buildings, either mildly damaging you or reducing your size. This would make the healing more relevant while making the shot spread feel more intentional. And then you could introduce an upgrade that reduces the damage your growths take, or similar.
Also, when I first saw the game, I was really hoping you'd be able to extend mycelia towards fallen enemies. That would add a whole new dynamic! But maybe that's a different game ;)
Super cool entry. Keep up the good work and keep making games!