Mahjong Solitaire — Pyramid

Tightly. A tile is free when nothing rests on top of it and at least one of its long sides is completely clear, and in a stepped pyramid that means the leftmost and rightmost tile of each row, and nothing else. The front and back rows of a step are blocked exactly like the middle ones, because a tile in a straight run has a neighbour on each side. Sixteen of the ninety-six base tiles are free at the start; the other eighty are covered by the step above or hemmed in from both sides.

In practice you work the pyramid down its two sides, taking the small upper steps first to expose the wide base. The opening is not the narrow part: thirty-four tiles are free on the first move against the turtle's thirty-five. What is narrower is everything after it — about six legal matches at a typical point in a pyramid against seven in a turtle, and every one of them out on an edge.

It has fewer legal moves available at any given moment, which makes it feel harder and makes a careless removal more costly. It is not harder in the sense that matters most, though: every deal here is generated by removing pairs from a full board in a legal order and then reversing that order, so a solution always exists. Where a deal is lost, it is lost because of a choice, and the Shuffle button will rebuild the remaining tiles into a fresh solvable arrangement.

• Match two identical free tiles to remove them. Flowers match any other flower and seasons any other season — those eight are the only tiles that are not exact pairs.
• A tile is free when nothing is stacked on it and either its left or its right long side is unobstructed. A tile with neighbours on both sides is blocked even if nothing is on top.
• Prefer the match that frees the most new tiles. Blindly clearing the easy pairs is the usual way a solvable board becomes a dead one.
• Use undo without hesitation, and Shuffle if you reach a dead end. The reshuffle is generated the same way as the deal, so it is always solvable again.