This is really cool! Great use of the theme!
Something I noticed though is that the web version lagged a bit the first time a particle emitter was used. You might already know this and just didn't have time to address it, but in case you're unaware, web exports of Godot games lag a bit the first time a unique particle is rendered. The fix is pretty simple, just make a node hidden away somewhere that fires all your particles at the beginning of the game. The lag spike will technically still happen, but it'll be right after the game finishes loading so no one will notice it.