Building a database of chess positions // played moves while learning Rust at the same time. The database associates a FEN key with a set of movement statistics: movement played, times played, win rate for white, win rate for black, etc. This database can then be used as an opening book or for other purposes e.g. to enrich a chess engine.
Text, PGN of the game. I am note sure now but I think I am using some of the databases here. See the example test database that is parsed by the unit tests here.