The weakest of recommends on the basis of its unique core mechanic; it's fun to play with, but once the levels start to loop there's little incentive to keep going, and it's an extremely active/fiddly game for as slow and grindy as the permanent upgrades appear to be. This is by Stop_Sign of Idle Loops fame, and that game's a far better starting point to their work if you haven't played one of their games before.