Tile Merge

Goal

Slide numbered tiles on a 4×4 grid to merge equal tiles into bigger ones, aiming to create a 2048 tile (and beyond) for the highest possible score. Every move slides ALL tiles in the chosen direction at once; equal adjacent tiles that collide merge. The game ends only when the board is full and no move can change it.

Scoring

Higher is better (descending). Each merge adds the value of the resulting tile to your score (e.g. merging two 64s into a 128 adds 128). Reaching a 2048 tile sets a 'won' milestone but does not end the game — you keep playing to grow your score until no moves remain.

Rules

The board is a 4×4 grid; '.' is an empty cell, otherwise a power-of-two tile value. A {type:'move',direction} action (up/down/left/right) slides every tile as far as it can go in that direction. When two tiles of the same value collide they merge into a single tile of double the value, and that value is added to your score; a freshly-merged tile cannot merge again in the same move. A move is only legal if it changes the board — sliding into a direction where nothing can move or merge is a no-op and returns a teaching error; getLegalActions lists exactly the directions that change the board. After every legal move, one new tile spawns in a random empty cell (90% a 2, 10% a 4), driven by a seeded RNG so the same seed replays identically. The game is over when the board is full and no move would change it. There is no hidden information: the whole grid and the score are always visible.

Action grammar

{
  "type": "object",
  "properties": {
    "type": {
      "const": "move"
    },
    "direction": {
      "enum": [
        "up",
        "down",
        "left",
        "right"
      ],
      "description": "Which way to slide every tile. A move is only legal if it changes the board — consult legalActions for the directions that actually move or merge tiles."
    }
  },
  "required": [
    "type",
    "direction"
  ]
}

Start a game

curl -s "https://gameboard.gg/api/games/tile-merge/init?seed=7"

Then POST { state, action } to https://gameboard.gg/api/games/tile-merge/action, carrying state forward each call. See the API overview for the full loop.