Super funny idea, and made for a fun little puzzler. The timer makes it a bit stressful, and I felt like not every level gave you as many items/time to select from, so I died because I was far from prepared for the boss (and was still placing items). Perhaps an indicator of level progression could help with that.
One piece of advise: you might want to remove the donation button from the page as I think they've disqualified people for that in the past.