2048

Games like 2048 are built using a data structure called a 2D Array (an array of arrays). The grid is represented in memory as a 4x4 matrix of numbers.

When a player presses the "Left" arrow, the game processes each row individually.

1. It filters out the empty spaces (zeros).
2. It iterates through the remaining numbers, checking if adjacent numbers match (e.g., merging 2 and 2 into 4).
3. It pads the end of the array with zeros to keep the total length exactly 4.

But what happens when the player presses "Up"? Rather than writing entirely new logic for vertical merging, developers use a clever mathematical trick called Matrix Transposition.

1. The matrix is transposed (columns become rows, rows become columns).
2. The exact same "Left" arrow logic is executed on the new rows.
3. The matrix is transposed back to its original orientation.

By combining matrix transpositions and reversals, developers only have to write the complex merge logic once (for a left swipe), drastically reducing bugs and keeping the codebase clean.