Left and right, not top and bottom
Choose 3, 4 or 5 hazards on a 4×4 board. Hazards must touch both the left and right edges, while they must not touch both top and bottom edges together. Touching only the top, only the bottom, or neither is allowed. All 124, 475, 1048 legal layouts respectively are equally likely and remain fixed during a round. Connectedness is not required.
Legal and illegal edge patterns
With 3 hazards, A1, B2 and A4 is legal: it touches left, right and top, but not bottom. A1, B2 and D4 is illegal because it touches both top and bottom. B1, B2 and C4 is legal without touching top or bottom. Visible edge conditions constrain a complete layout, not a guaranteed safe cell.
Conditional value
Live value starts at 0.97 times the virtual stake. A safe reveal divides it by that cell’s exact conditional safe probability among the remaining compatible legal layouts. A hazard ends the round with zero return. Reveals change knowledge, not the hidden layout.
Collect and eligible choices
Collect is available after a safe reveal. Proven hazards are unavailable; proven-safe cells have probability 1 and add no value. A choice with next value above 1000 times stake is unavailable. When no eligible uncertain choice remains, the current value is banked automatically. The guard is not a promise that 1000×stake can be reached.
Expected return
Exact expected return is 97% for permitted stopping policies. The initial 3% reduction is applied once; conditional safe-branch compensation preserves expectation. Choosing coordinates or stopping changes risk and variance, not this expectation. A short session is not guaranteed to match it.
Wallet and manual restore
Settled balance and fractional payout carry persist in localStorage. Reloading during a round ends it without refunding its already deducted stake. Outside a round, refill restores 1000 coins when balance is below the smallest stake; it does not add 1000 or reset fractional carry. Hazard count, stake and refill are locked during play.
Frequently asked questions
Is this an operator website?
This independent KM 23 guide supplies its own free Edge Span Mines demo. Operator identity, domains, licence, apps, payments, support and commercial game equivalence have not been independently verified. No operator account or commercial link is supplied here.
What are the edge constraints?
Choose 3, 4 or 5 hazards on a 4×4 board. Hazards must touch both the left and right edges, while they must not touch both top and bottom edges together. Touching only the top, only the bottom, or neither is allowed. All 124, 475, 1048 legal layouts respectively are equally likely and remain fixed during a round. Connectedness is not required.
Can hazards touch the top edge?
With 3 hazards, A1, B2 and A4 is legal: it touches left, right and top, but not bottom. A1, B2 and D4 is illegal because it touches both top and bottom. B1, B2 and C4 is legal without touching top or bottom. Visible edge conditions constrain a complete layout, not a guaranteed safe cell.
How is value calculated?
Live value starts at 0.97 times the virtual stake. A safe reveal divides it by that cell’s exact conditional safe probability among the remaining compatible legal layouts. A hazard ends the round with zero return. Reveals change knowledge, not the hidden layout.
Explore the original free Edge Span Mines demo.
