| problem(difficulty, question, secret, puzzle, obscurity) |
| puzzle(noun, difficulty, question, secret, obscurity) |
| puzzlement(question, secret, puzzle, obscurity, subtlety) |
| question(difficulty, secret, puzzle, obscurity, subtlety) |
| rebus(difficulty, question, secret, puzzle, subtlety) |
| reconditeness |
| riddle(difficulty, question, secret, puzzle, obscurity) |
| rune(difficulty, question, secret, puzzle, subtlety) |
| secret(question, puzzle, perplexity, obscurity, subtlety) |
| sphinx(difficulty, question, secret, puzzle, perplexity) |
| stickler(difficulty, question, secret, puzzle, obscurity) |
| stumper(difficulty, question, secret, puzzle, perplexity) |
| subtlety(difficulty, question, secret, puzzle, obscurity) |
| teaser(difficulty, question, secret, puzzle, perplexity) |
| thriller(difficulty, question, secret, puzzle, subtlety) |
| twister(difficulty, question, secret, puzzle, obscurity) |
| unimaginable |
| whodunit(noun, difficulty, question, secret, puzzle) |
| why(difficulty, question, secret, puzzle, obscurity) |
| arcanum |