Minesweeper

Thirty columns, 16 rows, 99 mines. This is the classic "expert" minesweeper configuration that competitive players have been racing on for decades. Mine density hits 20%, which means one in five cells is lethal and the margin for sloppy play drops to zero.

Constraint counting becomes essential here. Single-number deductions run out quickly, and you need to compare overlapping number zones to make progress. The subtraction method — taking two adjacent numbers and working out how mines distribute between their unique and shared cells — is the primary tool. The strategy guide walks through it with examples.

The board is wide enough that distinct regions form. You'll often have two or three separate frontiers to work independently. When one stalls, switch to another. Coming back with fresh eyes after solving a different region frequently makes the stuck area obvious.

Hard boards on standard mode will occasionally contain a genuine 50/50 in the endgame. It happens. If guessing bothers you, the Einstein boards use the same 30×16 dimensions with 99 mines, but every cell is verified solvable. Same grid, no luck factor.