明るくなった

became brighter

→ 明るい
phrase Uncommon #13,339
became brighter Can describe something becoming physically brighter, or a person's mood, life, or surroundings becoming more cheerful. 明るくなった is the past form of 明るくなる.
JA: 朝になって、空が明るくなった。
EN: It became brighter as morning came.

空が明るくなった

The sky brightened.

稲妻部屋は時々明るくなった

The room was occasionally lit up by lightning.

部屋が明るくなった

The flowers brightened up the room.

伯爵来て以来あなたの明るくなった

Since the count arrived, your cheeks have brightened.

— お嬢さん (2016)

彼の顔は喜びで明るくなった

His face lit up with joy.

娘が帰って来たので彼の生活が明るくなった

His life became brighter when his daughter came home.