心眼儿 (xīn yǎn er): Heart (Noun) — Meaning & Stroke Order

He appears quiet on the surface, but deep down in his heart, he already has a meticulous plan.

Can't you see that every word he says is calculated and hides an ulterior motive?

She is clever and can always come up with good ideas.

Don't play tricks on him; he is an honest person.