Hanoi Stack comes from Sergii Nagin. Th object is to flip rings and stacks of rings to eventually land on the pole is size order - largest on the bottom.I did the first 25 levels in about 15 minutes.  They start getting interesting around level 50, as more rings are added to the grid.

Interesting:
1. Multiple rings of the same size are frequent.
2. When a stack joins another ring, it will invert completely.  Look at the last image. The green ring on top - that whole stack will flip onto the light blue ring.  That will leave the red, largest ring, on top.  I have no idea how many levels there are.  I've done about 120.  The last 25 took about 20 minutes.
https://apps.apple.com/us/app/hanoi-stack/id1478998981

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