YOU SAID:
I've came up with an idea
INTO JAPANESE
アイデアを思いつきました
BACK INTO ENGLISH
I came up with an idea.
INTO JAPANESE
アイデアを思いついた。
BACK INTO ENGLISH
I've got an idea!
INTO JAPANESE
アイデアを思いついた!
BACK INTO ENGLISH
I've got an idea!
Come on, you can do better than that.