Zendoku allows for mathematical trash-talk of the highest order. Eat our logic and taste our deductive reasoning. How’d you like them rational apples? It’s as vicious as number grids get.
It’s a two player race for Sudoku grid completion and for every 3x3 box, row or column you fill, your opponent is sent a screen-filling stylus-using or mic-blowing distraction - earning you precious extra seconds. Some are easy - tapping away paper tiles - but faced with chiseling away 30 minuscule stone blocks or tapping away a flurry of incoming cartoon fists, you soon enter into the swearing zone as your not-getting-any-fuller grid goads at you from behind the distraction. It’s malicious, delightful fun.
Jettisoning numbers for icons means each player has a “special icon” - when used, it stops incoming distractions and returns to sender. Revenge is sweet, and even sweeter when it comes courtesy of a sumo wrestler emoticon. It adds an element of icon hoarding into play - do you place icons immediately, making the grid instantly comprehensible, or do you store them for an attack deflection later on?
One move that may annoy Sudoku purists - but, hey, the game features a battle with Chuck Norris in heaven, so it’s hardly pandering to your average logic-lover - is that laying each icon anywhere else than its planned place in the grid is interpreted as guesswork and/or stupidity. You’re subsequently punished - by the game filling in the correct icons on your opponent’s grid. In effect you’re told outright when you’re making a mistake - unlike real Sudoku which will happily let you plow your way into a numerical grave. It isn’t real Sudoku, but it’s real fun.