shine "bright" / "brightly"

Hello Alan, Mister Micawber, Beeesneees, Mordant, Esl_Expert and other native English speakers,
The beach was filled with people on this day and the sun was shining [color=red]bright.

Isn’t “brightly” correct? Is “shine bright” an idiomatic expression?

According to the dictionaries, “bright” is both an adjective and an adverb, so you don’t have to add “-ly”. You can do it if you want, but it’s not necessary.

Thank you, Jamie.