It's a crossword puzzle where you need to fill in the hexes with character sequences, so that they match the regular expressions listed around the edges.
The individual clues will turn green when satisfied, red when not.





Javascript implementation by Jimb Esser. Source code available on GitHub, fork and add your own puzzles!
Original puzzle from: http://www.i-programmer.info/news/144-graphics-and-games/5450-can-you-do-the-regular-expression-crossword.html
Solution available here.
Best viewed in Google Chrome or Firefox. If you are using one of these browsers, your work should be saved if you refresh the page or come back later.