Related Clues:
- Hard nut to crack
- It's mysterious or difficult to understand
- Puzzler
- 'I'm a walking, talking ___': Larry David
- Some variations for the German war machine
- Challenging riddle
- Variation in game may need explaining
- See 16
- 'In' game with which to monkey puzzle
- Machine with gamma for chi when deciphered
- Play in game with variations
- Puzzle resolved in game
- ... which name disclosed a machine used in war
- Variation in game puzzles people
- Heartless meaning could be a riddle