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 only the outermost ring of each layer is ever available. The 96-tile base is almost entirely locked at the start — the middle of it is covered by the layer above and hemmed in on both sides.

In practice you work the pyramid from the top down, taking the capstone and the small upper steps first to expose the wide base. That makes the opening narrow and the endgame wide, which is the reverse of the turtle, where you have plenty of choice immediately and can run out of options at the end.

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.