Left: word 讠/言 (sound waves out of a mouth 口), right: administration 司 (... where sb. is sitting in a corner ⌝ throwing a sheet 一 of paper in the wastebasket 口)
Mnemonic
Words from the administration are the (permissible) words.
The app has many other functions, such as character selection according to difficulty, practice programs, handwriting recognition and success statistics!