Kanji depth most apps skip
We flag false friends like 勉強 / 丈夫 / 大丈夫 (same characters, different meanings in Japanese vs. Chinese), pair every kanji with its traditional and simplified Chinese forms (経 = 經 / 经), and expose phonetic-component patterns (巠 → ケイ). Most Japanese-learning apps treat kanji as decoration on top of readings; we treat the CJK overlap as core content. Especially useful if you've studied any Chinese.
