f61 Four-Mine Demo: Rules and Virtual Wallet

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.

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.

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 initial virtual balance is 1,000. At settlement, the game adds any previously saved fractional carry to the gross quote, pays the integer part into the wallet and saves the remaining fraction separately. Carry is a payout remainder, not a fee or fractional wallet balance. While idle with a balance below 10, manual refill sets the integer wallet to exactly 1,000 and preserves carry. Refill is not available during an active round.

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.