Checkers — Rules & board

type Piece = { player: 'red' | 'black'; type: 'man' | 'king' } | null;
type Board = Piece[]; // length 64

// Index formula: index = row * 8 + col
// Row 0 is the top of the board (black's back rank)
// Row 7 is the bottom (red's back rank)

// Starting positions:
// Black: rows 0–2 (indices 0–23, dark squares only)
// Red:   rows 5–7 (indices 40–63, dark squares only)

// Example: check what's at row 5, col 1
const piece = board[5 * 8 + 1];
// → { player: 'red', type: 'man' }

// Check if a square is playable (dark)
const isPlayable = (row: number, col: number) => (row + col) % 2 !== 0;