Left: white 白 (The shine ノ of the sun 日 makes it white), right: finished/complete: 完 (A roof 宀 needs an origin 元 (= groundwork, seating) to be finished and complete. [Origin: 元 =two 二 legs 儿]
The app has many other functions, such as character selection according to difficulty, practice programs, handwriting recognition and success statistics!