This was really fun. I actually went back to the beginning of the archive to find more puzzles to solve. I think it would be nice if when you have solved one of the historical puzzles it would give you a button to click onto the next day's puzzle.

I actually never came across the situation where my grid was unsolvable. As I was playing I was wondering what kind of algorithm you used to come up with grids that have no possible dead ends. Since this is clearly an issue, I wonder if it's possible to come up with puzzles that always have a solution similar to how the algorithm for creating Sudoku puzzles always guarantees it can be solved without guessing.