Blunder Watch plays back a real chess game from Lichess and challenges you to spot the blunders as they happen. Everyone gets the same game each day and competes on a shared leaderboard.

Scoring: React within 0.5s for 100 points, 1s for 90, 2.5s for 80. Miss a blunder and you score nothing. False positives cost 30 points.

Games are sourced from Lichess and pre-analyzed with Stockfish at depth 20. I use Lichess' definition of a blunder. Each game has 3-6 blunders.