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Sample chess game
=== Sample Game ===

 +---+---+---+---+---+---+---+---+
 | '''r''' | '''n''' | '''b''' | '''q''' | '''k''' | '''b''' | '''n''' | '''r''' | 8
 +---+---+---+---+---+---+---+---+
(contracted; show full)
 +---+---+---+---+---+---+---+---+
 | '''R''' | '''N''' | '''B''' |   | '''K''' | '''B''' |   | '''R''' | 1
 +---+---+---+---+---+---+---+---+
   a   b   c   d   e   f   g   h 


The game's first check!  There are three legal ways to respond to check:
#Capture the piece giving check.  Here this is impossible, as black has nothing which can move to h5.
#Interpose a piece between the king and the piece giving check.  Black could play 4... g6.  But that would lose a rook to 5. Qxe5+ and 6. Qxh8.
#Move the king out of check.  Note that moving the king to f7 leaves it in check, and it thus illegal.

Note that white has ''forked'' the king on e8 and the pawn on e5.
There is no time for black to protect both, so no matter what he does to get out of check, the white queen can take on e5.

4... Ke7

 +---+---+---+---+---+---+---+---+
 | '''r''' | '''n''' | '''b''' | '''q''' |   | '''b''' | '''n''' | '''r''' | 8
 +---+---+---+---+---+---+---+---+
 | '''p''' | '''p''' | '''p''' | '''p''' | '''k''' |   | '''p''' | '''p''' | 7
 +---+---+---+---+---+---+---+---+
 |   |   |   |   |   |   |   |   | 6
 +---+---+---+---+---+---+---+---+
 |   |   |   |   | '''p''' |   |   | '''Q''' | 5
 +---+---+---+---+---+---+---+---+
 |   |   |   |   | '''P''' |   |   |   | 4
 +---+---+---+---+---+---+---+---+
 |   |   |   |   |   |   |   |   | 3
 +---+---+---+---+---+---+---+---+
 | '''P''' | '''P''' | '''P''' | '''P''' |   | '''P''' | '''P''' | '''P''' | 2
 +---+---+---+---+---+---+---+---+
 | '''R''' | '''N''' | '''B''' |   | '''K''' | '''B''' |   | '''R''' | 1
 +---+---+---+---+---+---+---+---+
   a   b   c   d   e   f   g   h 

This move leaves black in a dangerous position, because his king is so exposed.
Furthermore, his rooks, bishops, and queen still have no way to get out.
The black position is no more developed than it was at the start of the game.

5. Qxe5+

 +---+---+---+---+---+---+---+---+
 | '''r''' | '''n''' | '''b''' | '''q''' |   | '''b''' | '''n''' | '''r''' | 8
 +---+---+---+---+---+---+---+---+
 | '''p''' | '''p''' | '''p''' | '''p''' | '''k''' |   | '''p''' | '''p''' | 7
 +---+---+---+---+---+---+---+---+
 |   |   |   |   |   |   |   |   | 6
 +---+---+---+---+---+---+---+---+
 |   |   |   |   | '''Q''' |   |   |   | 5
 +---+---+---+---+---+---+---+---+
 |   |   |   |   | '''P''' |   |   |   | 4
 +---+---+---+---+---+---+---+---+
 |   |   |   |   |   |   |   |   | 3
 +---+---+---+---+---+---+---+---+
 | '''P''' | '''P''' | '''P''' | '''P''' |   | '''P''' | '''P''' | '''P''' | 2
 +---+---+---+---+---+---+---+---+
 | '''R''' | '''N''' | '''B''' |   | '''K''' | '''B''' |   | '''R''' | 1
 +---+---+---+---+---+---+---+---+
   a   b   c   d   e   f   g   h 

Another check.
Black now has only one legal move.
He can't interpose anything between the king and queen, and he can't take the queen, so he must move his king out of check.
There is only one square next to the black king which the white queen is not attacking.

5... Kf7

 +---+---+---+---+---+---+---+---+
 | '''r''' | '''n''' | '''b''' | '''q''' |   | '''b''' | '''n''' | '''r''' | 8
 +---+---+---+---+---+---+---+---+
 | '''p''' | '''p''' | '''p''' | '''p''' |   | '''k''' | '''p''' | '''p''' | 7
 +---+---+---+---+---+---+---+---+
 |   |   |   |   |   |   |   |   | 6
 +---+---+---+---+---+---+---+---+
 |   |   |   |   | '''Q''' |   |   |   | 5
 +---+---+---+---+---+---+---+---+
 |   |   |   |   | '''P''' |   |   |   | 4
 +---+---+---+---+---+---+---+---+
 |   |   |   |   |   |   |   |   | 3
 +---+---+---+---+---+---+---+---+
 | '''P''' | '''P''' | '''P''' | '''P''' |   | '''P''' | '''P''' | '''P''' | 2
 +---+---+---+---+---+---+---+---+
 | '''R''' | '''N''' | '''B''' |   | '''K''' | '''B''' |   | '''R''' | 1
 +---+---+---+---+---+---+---+---+
   a   b   c   d   e   f   g   h 

White's queen is a dangerous attacker.
However, because it is too valuable to trade for anything, it can only take undefended pieces.
Everything in the black camp is defended by something, so the queen has done all she can do by herself.
It is time to bring in reinforcements.

6. Bc4+

 +---+---+---+---+---+---+---+---+
 | '''r''' | '''n''' | '''b''' | '''q''' |   | '''b''' | '''n''' | '''r''' | 8
 +---+---+---+---+---+---+---+---+
 | '''p''' | '''p''' | '''p''' | '''p''' |   | '''k''' | '''p''' | '''p''' | 7
 +---+---+---+---+---+---+---+---+
 |   |   |   |   |   |   |   |   | 6
 +---+---+---+---+---+---+---+---+
 |   |   |   |   | '''Q''' |   |   |   | 5
 +---+---+---+---+---+---+---+---+
 |   |   | '''B''' |   | '''P''' |   |   |   | 4
 +---+---+---+---+---+---+---+---+
 |   |   |   |   |   |   |   |   | 3
 +---+---+---+---+---+---+---+---+
 | '''P''' | '''P''' | '''P''' | '''P''' |   | '''P''' | '''P''' | '''P''' | 2
 +---+---+---+---+---+---+---+---+
 | '''R''' | '''N''' | '''B''' |   | '''K''' |   |   | '''R''' | 1
 +---+---+---+---+---+---+---+---+
   a   b   c   d   e   f   g   h 

This is an excellent move to keep the pressure on black.
Because it develops a piece and gives check, white prevents black from consolidating.

If white played less energetically with 6.Nc3, his advantage would evaporate instantly.
Black could answer with 6... Be7, giving the king room to retreat to f8.
Once black gets his king to safety, he might actually be winning.
White has only two pawns for the sacrificed knight, which leaves black at a material advantage.

6.... d5

 +---+---+---+---+---+---+---+---+
 | '''r''' | '''n''' | '''b''' | '''q''' |   | '''b''' | '''n''' | '''r''' | 8
 +---+---+---+---+---+---+---+---+
 | '''p''' | '''p''' | '''p''' |   |   | '''k''' | '''p''' | '''p''' | 7
 +---+---+---+---+---+---+---+---+
 |   |   |   |   |   |   |   |   | 6
 +---+---+---+---+---+---+---+---+
 |   |   |   | '''p''' | '''Q''' |   |   |   | 5
 +---+---+---+---+---+---+---+---+
 |   |   | '''B''' |   | '''P''' |   |   |   | 4
 +---+---+---+---+---+---+---+---+
 |   |   |   |   |   |   |   |   | 3
 +---+---+---+---+---+---+---+---+
 | '''P''' | '''P''' | '''P''' | '''P''' |   | '''P''' | '''P''' | '''P''' | 2
 +---+---+---+---+---+---+---+---+
 | '''R''' | '''N''' | '''B''' |   | '''K''' |   |   | '''R''' | 1
 +---+---+---+---+---+---+---+---+
   a   b   c   d   e   f   g   h 

Black makes an excellent move.
Never forget that moving the king isn't the only way to get out of check!

Admittedly, black's d-pawn is a dead duck.
It is worth the sacrifice, though, to open up lines for the queen and bishop so they can help with the defense.
Now if white fails to find the best continuation, black has some chance to counter-attack.

7. Bxd5+

 +---+---+---+---+---+---+---+---+
 | '''r''' | '''n''' | '''b''' | '''q''' |   | '''b''' | '''n''' | '''r''' | 8
 +---+---+---+---+---+---+---+---+
 | '''p''' | '''p''' | '''p''' |   |   | '''k''' | '''p''' | '''p''' | 7
 +---+---+---+---+---+---+---+---+
 |   |   |   |   |   |   |   |   | 6
 +---+---+---+---+---+---+---+---+
 |   |   |   | '''B''' | '''Q''' |   |   |   | 5
 +---+---+---+---+---+---+---+---+
 |   |   |   |   | '''P''' |   |   |   | 4
 +---+---+---+---+---+---+---+---+
 |   |   |   |   |   |   |   |   | 3
 +---+---+---+---+---+---+---+---+
 | '''P''' | '''P''' | '''P''' | '''P''' |   | '''P''' | '''P''' | '''P''' | 2
 +---+---+---+---+---+---+---+---+
 | '''R''' | '''N''' | '''B''' |   | '''K''' |   |   | '''R''' | 1
 +---+---+---+---+---+---+---+---+
   a   b   c   d   e   f   g   h 
⏎

⏎