So cute!! It has a real elegance and does so much with so little. I don't think I've ever beaten a game of minesweeper in my entire life so haven't internalized the logic, but the animal theme sexes things up a lot. I'm gonna play it again later and hopefully do less bad than I think I did in the first attempt.
Bearing in mind I don't fully understand minesweeper rules so I have no idea how actionable this suggestion is, but having feedback on animals as soon as they're "solved" would be juicy, flavourful and give more instant feedback on whether I'm actually playing properly. There's a game called Dorfromantik that feels oddly reminiscent of this that has lovely "PERFECT" text that appears when you surround a tile optimally.
This is really a personal preference thing - although I LOVE the sprites I generally prefer brighter colour palettes.
Also, a smaller/easier first level would help the dumbasses (like myself) get a nice easy win to test they understand the rules before dedicating more time to completing a big one, only to discover they didn't quite understand the goal (in particular, I didn't realise I needed to solve EVERY animal to not lose).