SIX POSITION CHESS DIAGNOSTIC SAMPLER
Constructed for this resource. No puzzle collection was used. Familiar motifs; not a claim of unprecedented positions.
Use a physical board or diagrams. No installation or account needed. Not a rating test.
Notation: K king, Q queen, R rook, B bishop, N knight; x capture, + check, # checkmate, =Q promote to queen.

1. Hanging piece - White to move
White: king g1, rook d1, pawns f2 g2 h2. Black: king g8, bishop d5, pawns f7 g7 h7.
FEN: 6k1/5ppp/8/3b4/8/8/5PPP/3R2K1 w - - 0 1
Question: Which black piece is undefended? Capture it with the rook. Can Black immediately recapture your rook?
Answer: The bishop on d5 is undefended. Play 1. Rxd5. No legal Black reply captures the rook on d5. This verifies an immediate material gain, not a forced win of the game.
Why: Before capturing, trace every enemy attack on the destination square. Here neither the black king nor a black pawn attacks d5.
Practice habit: Before my move, I will scan for undefended pieces on both sides.

2. Knight fork - White to move
White: king g1, knight d6, pawns f2 g2 h2. Black: king h8, rook d8, pawns g7 h7.
FEN: 3r3k/6pp/3N4/8/8/8/5PPP/6K1 w - - 0 1
Question: Move the knight so it checks the king and attacks the rook. Find Black's only legal reply, then capture the rook.
Answer: Play 1. Nf7+ Kg8 2. Nxd8. The knight on f7 attacks h8 and d8. After the check, ...Kg8 is Black's only legal reply, so the rook can be captured next.
Why: A knight check cannot be blocked. Black cannot capture the knight here, and g8 is the king's only legal escape square.
Practice habit: When I consider a knight check, I will look for a second target.

3. Absolute pin - Black to move
White: king g1, rook e1, pawns g2 h2. Black: king e8, knight e7.
FEN: 4k3/4n3/8/8/8/8/6PP/4R1K1 b - - 0 1
Question: Can Black legally play ...Nc8? Explain what would happen to the king. Name one legal Black move instead.
Answer: No. ...Nc8 would uncover the e-file and leave the black king in check from the rook on e1. The knight is absolutely pinned. One legal alternative is 1... Kf8; it is an example, not a best-move recommendation.
Why: A legal move may not leave your own king in check. In this position, every knight move leaves the e-file open.
Practice habit: Before moving a pinned piece, I will check the line to my king.

4. Back rank mate - White to move
White: king g1, rook e1, pawns f2 g2 h2. Black: king g8, pawns f7 g7 h7.
FEN: 6k1/5ppp/8/8/8/8/5PPP/4R1K1 w - - 0 1
Question: Give checkmate in one move with the rook. Explain why Black cannot capture, block or escape the check.
Answer: Play 1. Re8#. The rook checks along the eighth rank. It controls f8 and h8, while Black's own pawns occupy f7, g7 and h7. Black cannot capture the rook or block the check.
Why: Checkmate means the king is in check and the side to move has no legal move. Both conditions hold after Re8.
Practice habit: Before calling mate, I will test captures, blocks and king escapes.

5. Stalemate trap - White to move
White: king f6, queen f7. Black: king h8.
FEN: 7k/5Q2/5K2/8/8/8/8/8 w - - 0 1
Question: Compare 1. Qg6 and 1. Qg7. Which move stalemates Black, and which move checkmates? Check every king escape.
Answer: 1. Qg6 is stalemate: the black king is not in check and Black has no legal move. 1. Qg7# is checkmate: the queen checks h8, controls g8 and h7, and is protected on g7 by the white king.
Why: After Qg6, g8 and h7 are controlled by the queen; g7 is controlled by the queen and king. After Qg7, ...Kxg7 is illegal because the white king protects g7.
Practice habit: When my opponent has few moves, I will check for stalemate before moving.

6. Protected promotion - White to move
White: king f7, pawn g7. Black: king h7.
FEN: 8/5KPk/8/8/8/8/8/8 w - - 0 1
Question: Promote the pawn to a queen. Can Black capture the new queen? Name Black's legal reply to the check.
Answer: Play 1. g8=Q+ Kh6. The white king on f7 protects g8, so ...Kxg8 is illegal. After the promotion, ...Kh6 is Black's only legal reply. This is safe promotion, not checkmate.
Why: A king cannot capture a protected piece. The new queen controls g6, g7 and h8; the black king cannot stay in check on h7, and h6 is its only legal escape.
Practice habit: Before promoting, I will check whether the new piece can be captured.

