Most definitely a major challenge, even on the easy level. You never realize how dependant on number associations one is until you have to rely on symbols rather than #s. Stretches the brain! Thank you for the free app sale!
More annoying than fun. After completing a level (dunno what to call it) it went back to the 1st page so you have to tap your way back to the page you're currently doing. Not sure why would anyone play a sudoku with some random symbols. No option to completely turn off the sound either (sound effects are forced to be on). Meh.