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front side (of a piece of paper, coin, medal, etc.); obverse
A-side (of a record)
main levels (as opposed to secret levels or post-game content)
カードのオモテ面に名前を書いてください。
Please write your name on the front of the card.
オモテ面のデザインがとても凝っている。
The front design is very elaborate.
封筒のオモテ面に住所を書き忘れた。
I forgot to write the address on the front of the envelope.