Chess in 40 SecondsThe Englund Gambit trap
Black to move. Mate in 1.
Snort's queen just took on c3. His king is boxed in. Mate him.
Hint
White's king is boxed in by its own pieces.
Answer
Qc1# — Checkmate! The king is boxed in by its own pieces.
The idea
A king walled in by its own pieces can't run. Always look at the row behind it.
This chess trap is one of 30 quick puzzles in the Chess in 40 Seconds trainer: find the move on the board, get a hint if you're stuck, and learn the idea so you never fall for it in your own games.