Look out for the upcoming app Kanji Crush, and see what a Match-3 game can be using kanji! In the simplest mode you just match identical kanji, in the most challenging mode you match any kanji with the same onyomi - that'll make sudoku seem easy!! There are also reference views of the kanji grouped by level, radical and onyomi which are great for review. Stay tuned.
Oliver Rose in Kansai, Japan