huò rán kāi lǎng

豁然开朗 (豁然開朗)

suddenly see the light; to have an “aha” or eureka moment; be suddenly enlightened

Example:

大学时期，乔尼开始有机会用Mac做设计，那是一种豁然开朗的体验
dàxué shíqí, 约翰 kāishǐ yǒujīhuì yòng Mac zuò shèjì, nàshì yīzhǒng huòránkāilǎng de tǐyàn
During college, Jon began to have opportunities to use a Mac to design, and that was a refreshing, eye-opening experience