The Doko demo kanji quizz : a good teacher !
This is a very interesting program (not a real game) to study japanese, but it's necessary to know some basic vocabulory first and read/write kanas and some elementary kanjis. Because it's all-in-japanese, the first time you play can be a little bit difficult, but however, you'll enjoy training with this program.
Many ways to learn japanese :
a/ some japanese sentences are written on the left screen with an underlined word written in kanji ; you have to write how to pronounce it in kana on the right screen.
b/ some japanese sentences are written on the left screen with an underlined word written in kana : you have to write the good kanji on the right screen.
c/ to learn japanese, it's not necessary to know the name of the keys used in kanji, but however, you can improve you knowledges by writing on the right screen the name in kana of the key of some kanji written on the left key.
Example : 桜. It means "sakura" (cherry tree). The key is the left part of the kanji and means "ki" (tree). So, because you know the name of the key for the tree is "kihen", just write きへん on the right screen.
There are other ways in the program to train, such as find the contrary word of the one written on the left screen, and write it in kanji on the right one, and mini-games too to play with kanji.
There are four levels of difficulty : beginner, easy, normal and hard and you can first try to train wherever you want. It's also possible to test yourself once a week with questions about the previous (a), (b), (c) and other exercises to evaluate your own level and know where you have to be much better. A graph and a ranking are available too...
This is a very very good program I bought four years ago the first time I went to Japan, and that I sold later, and I'm proud today to train with it ; if you want to study japanese and already know some words, all kana and kanji, please buy it. No hesitation !
Japan 
