Pawn Races: chess endgame

Count both promotion routes and the checks afterward.

When both sides can promote, count moves for both pawns and consider the kings’ routes. Promotion with check can decide a close race. After either pawn promotes, calculate checks and captures rather than stopping at the promotion square.

• Account for whose move it is and any two-square advance.
• Check whether either promotion gives check.
• Consider underpromotion when the new piece’s movement matters.