Teeko

A razor-sharp abstract classic on a 5×5 board, invented by magician John Scarne. Each side has just four pieces: drop them, then slide them one square at a time. Line up four in a row — or a 2×2 square — before the AI does, and build the longest streak.

How to play

Each player has four pieces. First comes the drop phase: you and the AI take turns placing your four pieces one at a time on any empty square.

Once all eight pieces are on the board, the move phase begins: on your turn you slide one of your pieces to any adjacent empty square, including diagonally. Pieces are never removed — you only reposition them.

You win the round the instant your four pieces form a straight line of four (horizontal, vertical, or diagonal) or a 2×2 square. Watch for both shapes at once.

A win adds 1 to your streak and deals a fresh board; a rare position where no one can force four is a draw and keeps your streak; a loss ends the game. The AI plays sharper as your streak grows, and who moves first alternates each round.

Tips & strategy

Teeko rewards the center. The middle square sits on more winning shapes than any other cell — rows, columns, both diagonals, and four different 2×2 squares all run through it. Grab it early in the drop phase and every threat you build later has more ways to finish.

Hold two shapes in your head at once. A line of four and a 2×2 square are completely different geometries, so the piece that blocks one may hand you the other. Beginners guard only the straight lines and get caught by a quiet square forming in a corner — always scan for both.

The drop phase decides most games. Because you place your four pieces before anyone can move, a lazy drop can leave you needing to slide a piece the AI simply refuses to let past. Aim to finish the drop with your pieces already one slide away from two separate threats — that double threat is unblockable, since the AI can only cover one square per turn.

In the move phase, think about what a slide leaves behind. Moving a piece to complete a shape also empties the square it came from, and that gap can open a winning move for the AI. Before you slide, check that the vacated square is not the exact cell your opponent needs.

The AI here starts gentle and sharpens fast: below a streak of two it often drifts, but past ten it plays close to perfectly, and Teeko with perfect play is a draw — so the long streaks come from setting quiet double threats early, not from out-grinding the endgame.