noun, noun or participle which takes 'suru', intransitive verb
admiration; being impressed
Usually used as 感心する or 感心している, with に marking what impresses the speaker: skill, effort, attitude, insight, and so on.
彼女の勇気に感心した。
I was impressed by her courage.
先生は彼の観察力に感
The teacher admired his powers of observation.
na-adjective
Na-adjective use, often in approving phrases such as 感心な心がけ, praising someone's attitude or conduct.
困っている人を助けるとは、感心な心がけだ。
It is admirable of you to try to help people in need.
noun, noun or participle which takes 'suru', intransitive verb
astonishment; being appalled
Negative or ironic use: the speaker is struck by something shameless, excessive, or unacceptable. It can sound like reluctant or sarcastic admiration rather than genuine praise.
彼の無責任さには、悪い意味で感心した。
I was appalled, in a bad way, by his irresponsibility.
ここまで堂々と嘘をつけるとは、ある意味感心する。
I am almost amazed that he can lie so brazenly.