As any of the roughly six zillion books filled with the griddy number puzzles would attest, it's pretty tough to muck up sudoku. One of the reasons this type of mind-bender has literally swept the world by storm - at least the portion that still does word searches and crosswords and cryptograms - is that it's conceptually simple and immediately accessible. You have a 9x9 grid. You have some numbers. And you have to fill in the rest of the numbers so that every column, row, and smaller, 3x3 sub-grid contains the digits 1-9 with no repeats. No math or trivia knowledge required; just logic. That's all there is to it.
Above: What visual clutter? By the way, the little baseball heads in the way is what happens in multiplayer or boss battles.
It's tough to screw up, but your first reaction upon setting eyes upon Toon-Doku is that someone tried to do exactly that: tried really, really hard, in fact. It's mostly the fault of the tiny, fuzzy DS screen. It's one thing to have to make out numbers, but easily discerning a pie from a taco from a pizza from spaghetti can get really tricky. Sometimes, they even toss some busy wallpaper behind the transparent playfield, enabling the background to interfere with the symbols. To be fair, you can double-click a shoulder button to zoom in on one 3x3 grid at a time, but we found that view was actually too constricted - we were constantly forced to either scoot the grid around by hand or zoom back out and select a different area to magnify - neither of which were fun solutions.