Greetings! I tried to reply about 25 minutes after you opened the ticket 3 days ago – can you check your spam folder? Regardless, it is a great question so I’ll reply here!
So the “Bd1” you’re seeing is the move in “SAN notation” – in this case it’s saying “bishop to d1”. NCM used to show this notation by default, but we switched to SAN by default during our last major rewrite several months ago. You can always click on the move to have it executed on the board.
The other notation you mention (“b2b3”) is, best I can tell, is known as “Smith” notation. You can go in to settings and disable SAN notation to get back to the b2b3 notation.
As far as PGN and FEN –
These are both ways to represent, in text, the board. FEN and PGN are both standards used by lots of chess software, so they’re useful if you want to, for instance, copy your position from NCM into some other software or vise-versa.
The main difference between the two is that FEN is able to represent the current position on the board, while PGN is able to represent the complete history of the game.
Also I’m curious about the errors you were getting on the app! There are a couple of known bugs that can result in server errors that we need to fix:
- If you have an un-promoted pawn in the 8th rank, and
- If you’re using a Lc0 test71 network
Could it have been either of these? If you can send me the particular position I would love to take a look and push a fix!