GazelleGames does that with game covers. Lichess has one where you need to find ...

viceroyalbean on May 31, 2019 | parent | context | favorite | on: Ask HN: A Good Alternative for ReCaptcha?

GazelleGames does that with game covers. Lichess has one where you need to find a checkmate in one move. It's usually pretty easy, but could in theory be frustrating for someone just starting with chess.