Hourglass Mahjong

Two wide bowls joined by a narrow neck, with the sand piled up in the bottom bowl. It uses 136 tiles on 3 layers. Difficulty: Medium.

• The neck is only three tiles wide. Its end tiles open quickly and link the two halves.
• The sand in the bottom bowl is three layers deep. Start there; the top bowl is only two layers.
• The widest rows at the rims open from both ends.

• Match two identical tiles. Tap or click one tile, then its twin, and both leave the board.

• Only open tiles can move. A tile is open when nothing sits on top of it and its left or right side is clear. In this row the middle tile is blocked on both sides. Blocked tiles give a little shake when you tap them.

• Flowers match flowers, seasons match seasons. The four flower tiles all match each other, even with different pictures. The four season tiles work the same way.

Clear all 136 tiles to win. If no pairs are left, press Shuffle to rearrange the remaining tiles, or Undo your last moves. Every board is dealt so that it can be cleared. Read the full guide.

On a keyboard: Z undo, H hint, S shuffle, N new game.

• Open the long rows first. Tiles at the ends of long rows block the tiles beside them. Clearing the ends gives you more choices later.
• Uncover stacked tiles early. A tile that sits on top of others is worth more than a tile that blocks nothing. Prefer pairs that reveal new tiles.
• Choose carefully when three of a kind are open. Take the pair that frees the most tiles, and keep the third for later. When all four are open, remove them all.
• Save flowers and seasons. They match each other freely, so keep them for the moment you need to open a stubborn stack.
• Use the hint to learn. The hint suggests the pair that uncovers the most tiles, not just any legal move.