Corner strategy is the standard advice and it is correct. But 'keep the big tile in the corner' is a consequence, not an instruction. The actual instruction is about which keys you press.
Why fragmentation kills
A tile can only merge with an identical neighbour. A 256 that has drifted to the middle of the board needs another 256 adjacent to it, which means building a second 256 and then manoeuvring it alongside. That is expensive.
Meanwhile the stranded 256 occupies a cell permanently. Two or three such tiles and you are effectively playing on a 13-cell board, then an 11-cell board, and the end comes quickly.
The mechanic that makes corners work
Sliding in a direction pushes everything that way. If you only ever slide down and left, every tile is constantly being pressed toward the bottom-left. Large tiles accumulate there because they arrive first and nothing pushes them out.
The corner is not magic. It is simply the cell that two of your four directions both point at.
The three-direction rule
Pick a corner, then classify the four directions:
- Two primary directions — the two that point at your corner. Bottom-left means down and left. Alternate between these constantly.
- One safe direction — for bottom-left, right. Use it when neither primary direction changes the board. It does not disturb the bottom row.
- One forbidden direction — up. Pressing it lifts the bottom row off the floor and exposes the corner.
Why 'right' is safe and 'up' is not
Sliding right moves tiles away from the left wall but keeps everything on the bottom row. Your big tile slides along the floor but stays on the bottom, and one press of left restores it to the corner.
Sliding up moves everything off the floor. The big tile rises, a new tile spawns underneath it, and now there is a small tile between your anchor and the corner. That is how boards die.
Maintaining the anchor row
The bottom row should read in descending order from the corner: for example 512, 256, 128, 64. Each tile then has a smaller neighbour that can eventually double into a match.
When the bottom row is 512, 256, 128, 64 and you build another 64 above the last cell, one down-press merges them to 128, which then merges with the existing 128, and the chain collapses. That cascade is where large scores come from.
Keep the bottom row full
A full bottom row cannot be disturbed by a left or right press. A bottom row with a gap can shuffle, and that is when the anchor slips.
When you are forced up
Occasionally down, left and right all fail to change the board and up is the only legal move. This is the emergency. Before it happens, the goal is to always keep at least one primary direction available.
The way to guarantee that: never completely fill the board with mismatched tiles. Keep small tiles — 2s and 4s — in the upper area where they can merge freely, rather than letting them accumulate as dead weight.
If the corner is lost
Do not panic and do not start pressing randomly. Work to restore the largest tile to the corner with the minimum number of moves, accepting some loss of structure along the way. Undo is available for one move, which covers the common case of pressing up by accident.