Read from the edge you move toward
When moving left, inspect a row from its left edge. Empty spaces close before equal tiles meet. When moving right, start at the right edge instead. That difference matters when three equal tiles share a row: the pair nearest the destination edge combines first.
These examples show the row immediately after the slide, before the random tile is added. They are worked examples, not screenshots of a saved board.
| Starting row | Left result | Score added |
|---|---|---|
| 2 · 2 · 2 · — | 4 · 2 · — · — | 4 |
| 2 · 2 · 2 · 2 | 4 · 4 · — · — | 8 |
| 2 · 2 · 4 · — | 4 · 4 · — · — | 4 |
| 4 · — · 4 · 8 | 8 · 8 · — · — | 8 |
Why the new 4 does not immediately become 8
A newly merged tile cannot merge a second time in that move. In the third row above, the new 4 stops next to the existing 4. Another left move can combine them, provided the next board still allows it. Four 2 tiles therefore produce two 4 tiles, not one 8.
Our recorded Down move increased the score from 24 to 28 and left two separate 4 tiles in the right column. See the before-and-after screenshots for that actual session.
Score is the sum of merged results
Each merge adds the value of the resulting tile. Two separate 2+2 merges add 4+4=8 points. Sliding tiles without merging adds no points. The new random tile does not add score just by appearing.
A valid move adds a random tile somewhere on the board. A keypress that cannot slide or merge anything does not advance the board in this edition. When checking your prediction, distinguish the moved tiles from that newly spawned tile.
Try a direction comparison
For the row 2 · 2 · 2 · —, predict a right move. Before the new tile appears, the answer is — · — · 2 · 4. Both directions score 4, but they place the largest tile differently. That is why score alone cannot tell you which move better preserves your corner layout.
Try the next run
Use one idea from this guide in the 2048 player. Its game page includes controls and edition/source details.