Welcome back. Perhaps you'd like to tell me what you'd like me to call you this lesson.

Have you learnt all about PAWN PROMOTION, kiddo?

Yes, I understand about PAWN PROMOTION.

I don't understand PAWN PROMOTION

There just one more rule you need to know before you can play a real game of chess, and it's an important one.

It's called CASTLING.

CASTLING is a double move of king and rook which each player can do once in a game. Watch carefully to see how it works.

You can CASTLE if:

1. Your KING has never moved.
2. Your ROOK has never moved.
3. There are no pieces between the KING and the ROOK.
4. You are NOT in CHECK at the moment (it doesn't matter if you've been in check in the past).

When you CASTLE you move your KING TWO SQUARES towards the ROOK, and, in the same move, transfer your ROOK over the top to the next square.

Here's the position after both players have CASTLED.

White has CASTLED on the KING SIDE. Black has CASTLED on the QUEEN SIDE.

You'll notice that the black king is nearer the centre while the white king is nearer the corner.

Some more CASTLING rules:

You CANNOT CASTLE if your king would end up IN CHECK. (Of course you can't play ANY move which would leave your king IN CHECK.)

Here, White CANNOT castle because it would put his king IN CHECK from the black bishop.

The hardest part of the CASTLING rule to understand is this:

You CANNOT CASTLE if the square your king crosses is attacked by an enemy piece.

In this position, Black CANNOT CASTLE because his king would cross over the d8 square, which is attacked by the rook on d1.

That's the end of the lesson, kiddo.

Guess what? It's time for a REALLY HARD EXAM about CASTLING.

CASTLING is hard but I think I get it.

Can I repeat the lesson first?

I'll do it later - I have to go now

I'll never understand CASTLING: it's too hard for me.