Opipopi is a short point-and-click adventure game where the player spends time in their room before falling asleep. Players can interact with various objects in the room in any order. Each interaction increases the character's "sleepiness." Once the sleepiness reaches a certain level, the night ends, and time progresses. The game features three different endings, which branch depending on whether the player discovers specific elements in the room before falling asleep. Hints for unlocking these conditions are hidden within the game's UI, such as backlog text colors and speech bubble shapes. The average playtime is 15 to 20 minutes per playthrough.