[pimlottc]

I was surprised that it automatically fills in the blank spaces once you mark all the filled ones, I haven't seen that in other PBN games. As a test, I tried solving one by only marking all the blanks, sadly it didn't fill in the remaining squares for me... :)

One minor UI suggestion: you should allow filling (or marking empty) multiple boxes by holding the mouse button down. This makes it easier to fill in entire rows or columns.