Solution
38. ♚f1 ♛e8 39. a8=♛ ♛xa8 40. ♜xa8+
The position
This advanced puzzle (rating 2154) asks White to move to find the winning idea. It features these themes: Promotion.
It is White to move. Look for the tactic hiding in the position — Promotion. Drag a piece on the board to play your move; the puzzle will tell you if you found the best continuation.
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