WordFind where the fun way you can learn many curiosities, which you might not have heard about yet. In the free version you have 2 puzzles in each of the supported languages: Slovak, Czech, English, German, Polish. 28 additional puzzles can be purchased directly in the application.
Search words are not presented directly as text, but as an image. Each of them you can touch to access help, where you can find the search word in written form at your disposal as well as its translation into supported languages. That way you may learn something more as an addition to the actual crossword solving.