I'm not a huge fan of one puzzle games. They can be cute enough for a brief diversion, but once the player figures out the puzzle there's little enough left to the imagination. The key to this game (pun intended) is simple enough. After that it is a tedious matter to type in the variations to determine the unique solution.
Despite the utter tedium, which would normally earn a one star rating, I gave this game two stars simply because it was very well executed.
The author deserves credit for putting together such a clean, lean game. However, I really want more fiction in my IF.