Game Description

Classic Tic-Tac-Toe

Two players take turns placing their marks — X (crosses) and O (noughts) — on a 3x3 grid. The first player to get three marks in a row (horizontally, vertically, or diagonally) wins. If all nine cells are filled with no winner, the game is a draw.

 X _ O        X wins with a diagonal:
 _ X _
 O _ X        X . .
              . X .
              . . X

Classic tic-tac-toe is a solved game: with perfect play, it always ends in a draw. It’s a great introduction to strategy games, but once you learn the optimal moves, there’s nothing left to explore.

Ultimate Tic-Tac-Toe

Ultimate Tic-Tac-Toe (UTT) reinvents the game by nesting boards inside boards.

The Board

Take nine small 3x3 boards and arrange them in a 3x3 grid. This gives you 81 cells total — a board of boards. Each small board is called a block:

   0 1 2   3 4 5   6 7 8

0  _ _ _ | _ _ _ | _ _ _
1  _ _ _ | _ _ _ | _ _ _
2  _ _ _ | _ _ _ | _ _ _
  _______|_______|_______
3  _ _ _ | _ _ _ | _ _ _
4  _ _ _ | _ _ _ | _ _ _
5  _ _ _ | _ _ _ | _ _ _
  _______|_______|_______
6  _ _ _ | _ _ _ | _ _ _
7  _ _ _ | _ _ _ | _ _ _
8  _ _ _ | _ _ _ | _ _ _

Each block is a 3x3 tic-tac-toe game on its own, but not independent ones: they are connected with an important rule.

Levels of Play

The board is a hierarchy of levels, numbered from the top (0) down:

• Ground (the deepest level) — individual cells where you place marks. Get three in a row within a block to claim it on the level above.
• Middle levels — present at depth 2 and beyond. Each middle-level block is won by claiming a line of blocks on the level below it.
• Peak (level 0) — the single cell at the very top. Win a line of blocks on level 1 to claim the peak and win the game.

In classic tic-tac-toe there are just two levels: ground (#1) and peak (#0). In Ultimate XO the ground is level #2, there is one middle level (#1), and the peak is #0.

The Key Mechanic: Allowed Area

Here is what makes Ultimate Tic-Tac-Toe truly strategic: your move determines where your opponent must play next.

The rule is simple: look at the position of your mark within its block. Your opponent must play in the block that occupies that same position on the large grid.

Example. X plays in the center cell of the top-middle block (cell at column 4, row 1). The center position within that block is (1,1) — middle column, middle row. So O must play somewhere in the center block (the one at position (1,1) on the large grid):

   0 1 2   3 4 5   6 7 8

0  _ _ _ | _ _ _ | _ _ _
1  _ _ _ | _ X _ | _ _ _       X played at position (1,1)
2  _ _ _ | _ _ _ | _ _ _       within the top-center block.
  _______|_______|_______
3  _ _ _ |[_ _ _]| _ _ _       O must now play somewhere
4  _ _ _ |[_ _ _]| _ _ _       inside the center block,
5  _ _ _ |[_ _ _]| _ _ _       marked with [ ].
  _______|_______|_______
6  _ _ _ | _ _ _ | _ _ _
7  _ _ _ | _ _ _ | _ _ _
8  _ _ _ | _ _ _ | _ _ _

Every move is a double decision: you’re placing your mark to advance your position in the local block, but you’re also choosing which block to send your opponent to, choosing their allowed area.

Free Moves

If you are sent to a block that is already won or completely filled, you get a free move — you can play in any block that still has available cells. This is critical to strategy: forcing your opponent into a won block gives them freedom, so sometimes “winning” a block at the wrong moment helps your opponent more than it helps you.

Game Over

The game ends when a player claims three blocks in a row on the peak grid (horizontal, vertical, or diagonal) — just like winning classic tic-tac-toe, but with whole blocks as the marks. If all blocks are resolved and no one has three in a row, the game is a draw.

Why It Works

The allowed area mechanic transforms every move into a trade-off. A strong local move might send your opponent exactly where they want to go. A weak-looking move might force your opponent into an impossible position. This tension between local tactics and global strategy is what makes Ultimate Tic-Tac-Toe genuinely deep — unlike classic tic-tac-toe, it has no known optimal strategy.

TacticToy Generalizations

TacticToy takes Ultimate Tic-Tac-Toe and generalizes it along every axis. The same position-constraint mechanic applies, but the board shape, depth, and rules can all be configured.

Larger Boards (Side Length)

Why limit blocks to 3x3? TacticToy supports any side length from 2 to 16.

• 2x2 — fast, aggressive games with no room for draws.
• 4x4 or 5x5 — more breathing room, longer games, richer tactical possibilities.
• 15x15 with line length 5 — this is Gomoku (five-in-a-row), a classic game in its own right.

A small excerpt from a 4x4 board nested 2 levels deep:

   0 1 2 3   4 5 6 7   8 9 a b   c d e f

0  _ _ _ _ | _ _ _ _ | _ _ _ _ | _ _ _ _
1  _ _ _ _ | _ _ _ _ | _ _ _ _ | _ _ _ _
2  _ _ _ _ | _ _ _ _ | _ _ _ _ | _ _ _ _
3  _ _ _ _ | _ _ _ _ | _ _ _ _ | _ _ _ _
  _________|_________|_________|_________
4  _ _ _ _ | _ _ _ _ | _ _ _ _ | _ _ _ _
5  _ _ _ _ | _ _ _ _ | _ _ _ _ | _ _ _ _
...

Custom Line Length

The number of marks needed to win a block doesn’t have to equal the side length. You can set line length independently:

• Line = 3 on a 5x5 board means three in a row is enough — more winning possibilities, faster games.
• Line = 5 on a 15x15 board gives you Gomoku rules within each block.

Deeper Nesting (Depth)

Ultimate Tic-Tac-Toe has depth 2: blocks inside a board. TacticToy supports up to depth 4.

Depth 3 means blocks within blocks within blocks. With side 3 and depth 3, you get a 27x27 grid with 729 ground-level cells. The allowed area cascades through all levels: your cell position within the innermost block determines which mid-level block your opponent must play in, and from there which innermost block within that block.

  0 1   2 3    4 5   6 7         A 2x2 board with depth 3.
                                 Double lines || separate
0 _ _ | _ _ || _ _ | _ _        the top-level blocks.
1 _ _ | _ _ || _ _ | _ _        Single lines | separate
 _____|_____||_____|_____        the mid-level blocks.
2 _ _ | _ _ || _ _ | _ _
3 _ _ | _ _ || _ _ | _ _
 _____|_____||_____|_____
 _____|_____||_____|_____
4 _ _ | _ _ || _ _ | _ _
5 _ _ | _ _ || _ _ | _ _
 _____|_____||_____|_____
6 _ _ | _ _ || _ _ | _ _
7 _ _ | _ _ || _ _ | _ _

At depth 3 and beyond, you must think on three or more strategic levels simultaneously. Each move sends your opponent to a specific position on every level of the hierarchy.

Higher Dimensions

Flat 2D boards are just the beginning. TacticToy supports 3D and 4D play.

3D — imagine stacking several 2D slices to form a cube. A 3x3x3 board has 27 cells, and winning lines can run along any of the three axes or through any of the four 3D diagonals. A classic 3x3 board has 8 possible winning lines; a 3D cube has 49.

A 3x3 board in 3D is displayed as side-by-side slices:

  # Z = 0:     # Z = 1:     # Z = 2:

  _ _ _        _ _ _        _ _ _
  _ _ _        _ _ _        _ _ _
  _ _ _        _ _ _        _ _ _

4D — a tesseract. Cells are addressed by four coordinates (x, y, z, t). A 3x3x3x3 board has 81 cells with 272 possible winning lines. It is displayed as a matrix of 2D slices indexed by Z and T.

More Teams

TacticToy supports up to four teams playing on the same board:

Multi-team games introduce alliance dynamics, king-making, and threat balancing that don’t exist in two-player games. Blocking one opponent might help another. You have to consider everyone’s strategy, not just your own.

Notation

Board configurations use a compact notation with four parameters:

When a value equals its default, it can be omitted. Examples:

• S3 N1 — classic 3x3 tic-tac-toe
• S3 N2 — Ultimate Tic-Tac-Toe (81 cells)
• S3 N3 — Meta Tic-Tac-Toe (729 cells)
• L3 S4 N2 — 4x4 blocks, 3-in-a-row to win each, nested 2 deep
• L5 S15 N1 — Gomoku (15x15, five in a row)
• S3 N1 D3 — Classic tic-tac-toe on a 3D cube
• S3 N2 D3 — Ultimate Tic-Tac-Toe on a 3D cube

Quick-Start Presets

TacticToy provides built-in presets for common configurations:

How to Play

Local play — Two or more players on the same device, taking turns.

Against AI — Four difficulty levels from casual to really hard. The AI uses efficient algorithms of game-tree search instead of dumb scripted moves.

Online multiplayer — Create or join games with invite codes, chat with opponents, and play in real time with WebSocket push updates.

Tutorial — Three interactive lessons walk you through the allowed area mechanic, board depth, and dimensions with animated demonstrations.