This is a fairly fun game, and the concept is on point with the theme. Waiting for the right moment to harvest is a fun game dynamic in itself. Good stuff!
Here are a few suggestions I have if you plan to revisit this:
You might be able to make the earlier levels bigger on screen, so they don't feel so small. (However, that does mean your mouse would have to travel further to reach the next mushroom.)
Perhaps replace the timer-based fail condition with a threshold meter? I would rather see the room overflow with mushrooms due to my own failure of not harvesting them fast enough, rather than have them automatically fill the room when time's up. You might communicate this with a visual meter, accompanied by some neighbor dialogue bubbles at certain points, with messages like "What's that smell?" and "I think there's something going on with the neighbor." to "I'm filing a complaint."
The sound effects are great; consider adding some fitting music. ;)
Overall, nice entry, and good luck!