f61 Four-Mine Demo Review: Rules and Evidence

This guide explains its own virtual-coin browser demo on f61.top. An outside operator, business identity, licence, official app or payment service for the queried name has not been established. The source-observable game and wallet rules described here do not verify an outside service or provide a verdict on its reputation.

The board has four rows, four columns and exactly four mines. Number columns from zero on the left. Columns 0 and 2 must have the same parity of mine count and different counts; columns 1 and 3 must have the same parity, but their counts may be equal. Matching parity allows two odd counts as well as two even counts. There are 370 legal boards. One is sampled uniformly when a round starts and remains fixed throughout that round.

After a safe reveal, the game retains only boards consistent with all safe cells revealed so far. Gross quote = 0.96 × captured stake × 370 / remaining compatible boards. Gross includes the stake; net change is gross minus the stake. A mine pays zero gross. Revealing the top-left cell first and finding it safe leaves 269 compatible boards, so the quote is about 1.3204× stake.

The exact expected gross return is 96% of the captured stake under the uniform legal-board model. It is neither a win probability nor a guarantee for an individual round or session. Six offline reveal-and-stop paths have 20 million saved simulated rounds in total: five paths have one million each and the final path has fifteen million. Their measured gross returns range from 95.7856% to 96.0889%. These sample paths are not six selectable game modes.

Choose a virtual stake of 10, 20, 50, 100 or 200; the initial selection is 20. Starting a round immediately deducts and saves the captured stake. Stake, mine setting and refill are locked during play. Covered eligible cells and the sound control remain available. The bank button becomes available after at least one safe reveal. There is no automatic queue of rounds and no selectable mine count other than four.

You can bank manually after the first safe reveal. Revealing all twelve safe cells or having no eligible reveal remaining banks the current quote automatically. Proven mines and previously revealed cells are unavailable. An individual move whose prospective quote would exceed 1,000× stake is disabled. With this particular 370-board support, however, the maximum reachable quote is 355.2× stake, so the 1,000× guard is never reached.