A sneaky puzzle by grandmaster Sammy Reshevsky. White to mate in two moves.

# Puzzles

# Zigzag

From Lee Sallows:

# Unfinished

A puzzle by David L. Silverman:

On the back of an envelope you find an interrupted game of tic-tac-toe (noughts and crosses). You know that each player was an expert, which means that she never puts herself into a potentially losing position and that she always wins if her opponent gives her the opportunity. There are two Xs and two Os in the diagram, and it is impossible to tell whose move it is. Neglecting symmetry, what is the position?

# Podcast Episode 200: Lateral Thinking Puzzles

Here are five new lateral thinking puzzles — play along with us as we try to untangle some perplexing situations using yes-or-no questions.

# Two by Two

In poker, suppose you’re dealt a pair. Is the probability that your opponent also holds a pair higher, lower, or the same as it would be if you held nothing?

# Black and White

The English occultist Aleister Crowley, “the wickedest man in the world,” was a skilled chess player. In 1894 he published several problems in the *Eastbourne Gazette* under the pseudonym Ta Dhuibh. This one appeared on Feb. 21. How can White mate in two moves?

# A Royal Tour

A problem by Kagen Schaefer:

Suppose a king tours a chessboard, visiting each square once, never crossing his own path, and finishing where he starts. Inevitably he’ll have to make some horizontal and vertical moves; for example, in the tour above he makes 14 horizontal and 16 vertical moves.

Show that in any such tour of an 8 × 8 chessboard the sum of the horizontal and vertical moves must be at least 28.

# Black and White

By Aladár Erdey. White to mate in two moves.

# Black and White

By Eugène Ferber, 1899. White to mate in two moves.

# Black and White

By Carl Bilfinger. White to mate in two moves.