2048

2048 arrived in 2014, was written in a weekend, and consumed an improbable number of working hours in the months after. It is a sliding puzzle with one rule, and the reason it spread is that the rule produces far more game than it has any right to.

Four by four grid. Swipe in any direction and every tile slides that way until it hits a wall or another tile. Two tiles with the same number that collide merge into their sum — two 2s make a 4, two 4s make an 8 — and after every move a new tile appears in a random empty cell. A goal tile next to your score shows what to build next, starting at 128 and doubling each time you reach it. Make the 2048 tile and you have won: confetti, then a choice to keep going on the same board for 4096 and beyond, or deal a fresh one. Undo takes back a move, and you get two free per game.

The strategy that matters is easier to describe than to hold to. Pick a corner and keep your largest tile there permanently, building a descending row along one edge. Use only three directions — the fourth would pull your big tile out of its corner — and merge upward along that row. Almost every loss traces back to a moment of impatience where someone swiped the forbidden direction because it made one convenient merge.

The danger is the board filling up. Every move spawns a new tile, so a board with no merges available is a board a few moves from over. Keeping small tiles clustered and merging them promptly is what buys you the space to keep working the big ones. A grid with plenty of empty cells is a grid with a future, regardless of your score.

Runs last a few minutes and end abruptly. Arrow keys on desktop, swipe on mobile, and no timer at any point — you can stare at a board as long as you like before committing. The one-more-try pull is well documented and entirely real.