Board Control & Square Tension Methodology

Square control measures how many pieces can capture on—or defend a friendly piece occupying—each square from a1 to h8.

• Pawns: Project force strictly on their two forward diagonal capture squares (file ± 1), even when those squares are empty. Non-capturing forward pushes do not count as square control.
• Knights & Kings: Project force to all valid L-jump squares (up to 8) and adjacent king squares (up to 8), whether empty, friendly (defended), or enemy-occupied.
• Sliding Pieces (B, R, Q): Cast directional rays across files, ranks, and diagonals.

Naive ray-casters stop at the first occupied square, undercounting firepower when pieces are aligned in a battery. ChessTension resolves every tactical alignment case:

• Orthogonal Batteries (Files & Ranks): When a Rook or Queen encounters a friendly Rook or Queen along a file or rank, the ray continues through the aligned slider (supporting doubled Rooks, Rook + Queen, or triple stacks like Alekhine's Gun).
• Diagonal Sliding Batteries: When a Bishop or Queen encounters a friendly Bishop or Queen along a diagonal, the ray continues along the full diagonal.
• Pawn-Backed Diagonal Support (1-Step Propagation): When a Bishop or Queen stands behind a friendly Pawn along that Pawn's forward capture diagonal (e.g., Qd1 + Pe2 → f3 or Bb3 + Pc4 → d5), the slider projects 1 step through the Pawn to reinforce the Pawn's capture square and stops immediately after.
• Non-Matching Blockers: A Rook behind a friendly Bishop or Pawn on a file stops at the blocker because neither a Bishop nor a Pawn can capture along a vertical file.

To preserve the chessboard's diagonal readability while surfacing complete board control metrics, ChessTension uses four toggleable visual layers:

• All Control Mode: Flat stepped surface tints show net square dominance (W - B), paired with quiet corner numerals and bottom proportional force bars.
• Contested Mode: Isolates only actively contested battleground squares (W > 0 and B > 0) with a 1.5px amber inset border and a split tug-of-war bar along the bottom edge.
• Attack Rays Overlay: Solid directional vectors represent direct attacks, while dashed vectors (· Battery) indicate stacked or pawn-backed support.

Every square is classified into one of four mutually exclusive control states across the 64-square distribution bar:

• White-Dominated: Controlled exclusively by White forces (W > 0, B = 0).
• Black-Dominated: Controlled exclusively by Black forces (B > 0, W = 0).
• Contested Battleground: Targeted simultaneously by both White and Black (W > 0 and B > 0).
• En Prise / Hanging Alert (!): Flagged whenever an occupied non-King piece has strictly more enemy attackers than friendly defenders.