Fishing Pole Trap
A trap for Black in the Ruy Lopez: Berlin Defense, Fishing Pole Variation. White's natural-looking 6.hxg4 gives Black mate.
The moves
How it works
Taking the knight on g4 opens the h-file: ...hxg4 hits the knight on f3, and ...Qh4 with the rook behind it mates on h1 or h2.
What it wins
Black gets mate.
How White avoids it
The knight on g4 is bait: hxg4? hxg4 opens the h-file, and ...Qh4 mates. Leave it and play on with c3 or d4. The safe move is c3.
Practise the Ruy Lopez as BlackThe trainer plays the moves real players at your rating choose, and springs this trap when they do.