Unolingo, from Smithsonian.com, is a crossword puzzle in which you complete the words using each letter of the alphabet only once. There are no clues.
For example, if you decide the top word is STALKING, you use the letters A, L and G, which are then unavailable to complete any other words.
Puzzles with one star, like the one shown, are the easiest. The hardest have four stars.