Variants Puzzles and others: https://chessvariants.training/
https://altcodeunicode.com/alt-codes-math-symbols-italic-letters/
FoW: https://www.chess.com/blog/Illingworth/fog-of-war-chess-grandmaster-strategy
some crazyhouse study for future reference: https://lichess.org/study/OHSQPWgG
Klubok
4 Player Chess
50 460 Tag
Fog of War
5 768 Tag
Variants
4 467 Tag
8 Player Chess
919 Tag
4PC Teams
383 Tag