Eyy, thank you, and congrats on making a badass game ^^ It's not a new theme or genre but this still feels really fresh and emotionally affecting.
It took me a couple tries to understand the severity of the explosion mechanic, but honestly I didn't struggle with lvl 40 (i took the easy way out and didn't get perfect). This game strikes me as very easy if you're trying to pass levels, and very hard if you're trying to 100%. I gave up on perfect levels pretty early on, although it feels bad to let people die. I always did my best, but it was pretty hard. I'm not a big puzzle guy so take that with a grain of salt. I actually wonder... Is it possible to beat the game with no deaths? Or are there impossible rescues scattered around?
Oh yeah, and if you're looking for constructive criticism, I think it would be nice if the game explains the mechanic of: infected tiles building up to 4 levels of bubbles, and then exploding on the next turn into an impossible-to-destroy infection-source tile, damaging nearby structures. The sudden explosion confused me throughout gameplay, where my people suddenly died and I struggled to figure out what happened. I think I only figured it out in the last 5 or so puzzles. Also, I'm still not sure what some of the buildings actually do? Like the purifier and the amplifier.
Everything else, like the art direction, the music, the length of the game, the writing, the ui, and the game engine are basically perfect, nothing to note there :3
I hope you enjoyed making this and I hope you enjoy making more games in the future!