看他好像吃了一驚，她感到開心。
She had the pleasure of seeing him look surprised.
知道有人欣賞我所做的事真讓人開心。
It's nice to know that somebody appreciates what I do.
孩子們追逐著彼此的影子，玩得很開心。
The children were having fun, chasing each other's shadows.
我沒有察覺到你那么不開心。
I didn't realize you were so unhappy.
我沒有察覺到原來他那時非常不開心。
I didn't realize but he was deeply unhappy at that time.