I suspect that I only got good (not great) at Japanese due to its merciful consistency. Yet I still found myself forgetting certain verb conjugations at times, which is why I created this Ruby script to do it for me. The program is aware of いる and える verbs that are actually godan types, like 切る or 入る, but they must be presented with kanji to be recognized as such, even if the verb is normally written entirely in kana. You can see a full list of these words in the source code, including some exceptionally rare characters that are never written in practice. You will also find that the simple-minded code does not attempt to decipher する or 来る, since these are edge cases most students have committed to memory. Keep in mind that it is possible to generate nonsense words depending upon what options you select. Use it sensibly.