AITechnology

How Chess AI Works: Minimax & Alpha-Beta Explained

Ever wonder how a computer decides its next chess move? It uses an elegant algorithm called Minimax.

The Game Tree

Imagine every possible move as a branch in a tree. At each level, White tries to maximise their score; Black tries to minimise it. The computer explores this tree to find the best move.

Evaluation Function

At each leaf position, the AI calculates a score based on: material (Queen=900, Rook=500, Bishop/Knight≈320, Pawn=100) and piece-square tables (bonuses for pieces in good positions — knights in the center, rooks on open files).

Alpha-Beta Pruning

The tree grows exponentially. Alpha-Beta pruning skips branches that can't possibly improve the result — making the AI up to 100× faster without losing any accuracy.

Our Difficulty Levels

  • Newbie: 1 move ahead — makes occasional blunders
  • Easy: 2 moves ahead — plays reasonable moves
  • Normal: 3 moves ahead — consistent tactics
  • Hard: 4 moves ahead — strong positional play

Can you beat the Hard AI? Try now →