A move that doesn't respect the rules of chess.

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5
votes
2answers
259 views

Why is castling through and out of check prohibited?

Why is castling disallowed when the king is in check or when the square the rook will be placed on is under attack? What is the rationale behind this ruling?
3
votes
2answers
255 views

What “double moves” are sometimes considered legal?

As we know, castling is a legal "double move," where two pieces are moved at once. But in my country, Indonesia, in my childhood, the opening below was an 'assumed legal' double move to counter 1.e4 ...
11
votes
3answers
2k views

illegal (?) move can put a king in check?

I was playing a game with a friend online. A situation came up where he put me in check with his bishop, and I moved my rook to block it. His king was on the g file and my rook was on g2. The website ...
5
votes
1answer
100 views

Why isn't the active color allowed to be in check in a FEN legal position?

The title says it. Reading up on how to describe the position of a board, all of the requirements make sense (like two kings not being on adjacent squares and so on) except for the active color being ...
11
votes
3answers
650 views

How to know when a FEN position is legal?

I am doing a personal project, where at one point I need to validate the FEN position, I started with some basics checks, such as check if there are kings and making sure there aren't any extra rows ...
16
votes
2answers
1k views

I made an illegal move. What happens?

Especially in blitz or bullet games, it is possible that a player makes an illegal move, for example castles through check. If the opponent does notice the illegal move, then as far as I know the ...