Light Up (Japanese:美術館 bijutsukan) is a binary-determination logic puzzle published by Nikoli. As of 2006, two books consisting entirely of Light Up puzzles have been published by Nikoli.
The Hardest Logic Puzzle Ever is a title coined by George Boolos in La Repubblica 1992 under the title L'indovinello più difficile del mondo for the following Raymond Smullyan logic puzzle: “ Three gods A, B, and C are called, in some order, True, False, and Random. True always speaks truly, False always speaks ...