This is mahjong solitaire, the single-player tile-matching puzzle, not the four-player gambling game of the same name. The two share a tile set and nothing else. There are no hands, no draws from a wall, no scoring for combinations and no opponents. Instead, one hundred and forty-four tiles are stacked into a layered arrangement and your job is to clear the whole pile by removing identical tiles two at a time.
The layout used here is the classic turtle, sometimes called the dragon: a broad rectangular base with tiles piled several layers deep through the middle and single tiles trailing off each end. Because tiles overlap, most of the pile is locked at the start and only a fraction of it can be touched.
The tile set is the standard one: three suits of nine values with four copies each, giving one hundred and eight; four winds and three dragons, four copies each, giving twenty-eight; and eight bonus tiles made up of four flowers and four seasons.
Tiles sitting on the upper layers block the most other tiles. Removing them opens up the largest number of new options, whereas clearing a pair from the long side arms usually opens nothing at all. When you have a choice between two identical matches, take the higher one.
Every ordinary tile exists in four copies, so most matches are really a choice among several. If three copies of a tile are currently free and the fourth is buried, matching two of the free ones leaves one free copy waiting for the buried one, which is fine. But if two copies are free and two are stacked directly on top of each other in a single column, clearing the free pair strands the other two permanently, because the lower one can never be exposed while its twin sits on it. Scan for those vertical twins before you commit.
The bottom layer of the turtle contains long horizontal rows where only the two end tiles are ever free. These rows unlock slowly, one tile from each end at a time, so start chipping at them as soon as you can rather than leaving a twelve-tile row for the endgame.
Because any flower matches any other flower, those tiles are flexible and can rescue you later. If a flower is blocking something important, use it; otherwise leave the group intact for as long as it is convenient, since a flexible pair is worth more than a rigid one when the board tightens up.
The bar above the layout tracks how many tiles remain, how long you have been playing, and how many shuffles you have left. A hint highlights one currently available pair for a couple of seconds, which is useful when you suspect a match exists but cannot spot it among a hundred tiles. You also get three shuffles per game: a shuffle redistributes the remaining tiles across the same positions, which is your escape hatch when the board deadlocks with tiles still on it. Use them sparingly, because a shuffle can just as easily produce another dead position.
Each new game deals a fresh arrangement, so the difficulty varies from deal to deal in the way it does with physical tiles. For a fuller walkthrough of layouts and tile types, read our mahjong solitaire guide.