One tile on the board wears a ring. Only that tile's row and that tile's column can move. Left and right arrows spin the row, up and down spin the column. On a phone you swipe the board.
The grid wraps. A tile pushed off the right edge comes back on the left in the same move. Nothing falls off and the board never fills up, so there is no dead position. The only thing that runs out is moves.
Tiles combine when three of the same value fill a complete row or a complete column. They fuse into one tile in the middle cell, worth triple. Two matching tiles sitting next to each other do nothing. The ladder is 3, 9, 27, 81, 243, and a merge can set off a chain if it happens to complete another line.
The goal is a 243 tile within 90 moves. 243 is the top of the ladder, so reaching it ends the run.
Par is 80 moves. Any win inside 90 counts, 86 or fewer gets two stars, 83 or fewer gets three.
The ring travels with the tile it sits on, so the line you are allowed to move changes every single move. That is where the difficulty comes from: a row you have nearly finished can get broken up by a spin you were forced to make somewhere else.
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