Checkmate!

It is Checkmate when the King is in Check and:

1. The King can't capture the piece that has placed it into Check, because the piece that is placing the King in Check is protected by another piece.
2. The King can't move to another square to get out of Check, because those squares are controlled by other pieces.
3. You can't block the Check by moving a piece between the King and the piece that is checking the King.

A King cannot place itself into Check.

A King cannot place another King into Check.

If a King is in Check, it must move out of Check.

This is Checkmate.

The King is in Check by the Queen.

The King cannot move to get out of Check.

The King cannot capture the Queen, because the Queen is defended by the Bishop.

Checkmate!

The King is in Check by the Knight. The King cannot move to get out of Check. Checkmate!

The King is in Check by the Rook. The King cannot move to get out of Check. Checkmate!

CHECKMATE!