OpTac uses a chess engine and the Lichess opening database to find tactics (sequences of forced moves that change the evaluation). In this article I will describe the mode of operation and engineering challenges.
Starting from a specified position, it crawls the most common moves from the opening book up to some depth. Each position is checked with an engine for tactical opportunities. The results are outputted as puzzles and can be imported into a Lichess study.
This gives you an excellent tool to discover tricks and traps and learn the critical moves in your opening repertoire.
Below I will describe a few things I learned during the development of OpTac.
During the daily grind of puzzles on either Lichess or ChessTempo I never really had to think about what a tactic actually is.