Fairness

Before you choose your client seed, the server commits to a secret server seed by publishing its sha256 hash. That commitment is signed by the server and checked onchain when your round starts, so the server cannot swap the seed afterwards.

The mine positions are a shuffle of the tiles driven by sha256 of the server seed, your client seed and the round nonce joined together. Because your client seed is part of the input, the server could not have known the final board when it committed.

Every click is signed in your browser by a key made just for that round, and the program checks that signature before it accepts a bust. The server cannot invent a pick you did not make.

After the round the server seed is revealed onchain. Anyone can hash it, compare it with the commitment and recompute the board, which is exactly what the verifier above does.