Thank you very much for the good words and I'm really glad you liked the game...
The way the game is setup to allow for the daily challenges it is really hard to make sure there is a definite solution using all the keys... It was hard enough to make a seed based random generator since js does not support it ...
I like your suggestion about the keys... I haven't updated it in a while now, but it will be soon... Hopefully along with a mobile friendly version...