I really enjoyed the game! Awesome mix of Tetris and RPGs, never expected it and it turns out to be very fun. A lot of details to polish but that's one step at a time. Most of the suggestions I had were already commented, and I saw your reply that you will improve the combat system based on the Tetris match so well done!
Also, regarding the combat system most RPGs introduce the weakness concept. For example maybe the alligators should be weak to lightning and thus the spell cause double damage? Another interesting idea is that when you full completely the grid, you unleash a secret power that deals masssive damage.
These are just suggestions, your idea itself is unique. Keep it up!