writoids: how do you write a character? when, how and why would you write a complex character and when would you write a simplified one?

Characters are defined by or define the story. In a character driven story your character would obviously be complex, but they wouldn't start that way, not to the reader anyway. Their, well, character, develops through their reactions to events in the story.

A simplified character is for short stories where you rely on tropes or stories like (usually bad) fantasy or sci fi where the environment is so novel or strange that developing a complex character would be alienating to the reader.

Also secondary characters are obviously simplified