Left: feeling 忄, right: feeling 感 (When I have a "salty" 咸 heart 心" it is a: feeling.) [salty 咸 = The taste is for the person 人 (= ノ & 一) in the mouth 口 like a halberd 戈 such: salty.]
The app has many other functions, such as character selection according to difficulty, practice programs, handwriting recognition and success statistics!