Regular Expression Crossword Solver

The MIT Mystery Hunt 2013 included a hexagonal regular expression crossword (see the blog post here for a writeup).

I wrote a regular expression constraint propagation library in C# to solve it. The source code is on github. You can watch the program solve the puzzle below.

SPOILERS: if you want to solve this puzzle yourself (I'd recommend it; it's a good one), then don't watch the solver below, obviously.

Press "right" on the keyboard (you may need to give the grid focus first), or use the buttons at the bottom to control the solver.