Delightful! Really enjoyed this.
Expert use of the assets. Graphics are superb - it's complicated but I never lost track of what was happening.
It's a complicated concept, but I got it quickly. I think you dialed in the difficulty perfectly - the grade system lets almost anyone "beat it" but you can really play it very very hard. You really have a good feel for game difficulty.
Nicely done! Gonna try to get my kid to coop with me.