Left: tree 木, right: negative, sunset 莫 (The plants 艹 are made by the sun 日 to be large 大 [= as long shadows] at sunset.) [To compare: sunrise is: 旦 or ]
Mnemonic
(When producing identical parts, the clay is pressed into a concave counter mold.) Wood is used as a 'negative'-mold for making a standard model.
The plants 艹 are made by the sun 日 to be large 大 [= as long shadows] at sunset. - The very similar radical stands for sunrise. This seems bizarre, but can be argued based on the characters for morning 朝 in comparison to evening 暮.
The app has many other functions, such as character selection according to difficulty, practice programs, handwriting recognition and success statistics!