Very cool game. It's about as challenging as a mid-level sudoku - all the information you need is there, the real challenge is figuring out where to start filling in the blanks. Others have mentioned this, but I feel it bears repeating - the brown/green color that marks the left side of the squares on levels 9 and 10 are INCREDIBLY hard to tell apart for color blind people. I had to work out from the shape of the puzzle which was which, as I couldn't tell at a glance which was which.
 "Dynetzzle"){kind=icon}
 "Take Something Literally"){kind=icon}