Co-Open is a charming simulation game set on Windows that invites players to experience a child's first solo grocery shopping trip. Players explore a cooperatively run store filled with community-selected products, offering a unique variety that may not always meet expectations, encouraging discovery and surprise. The gameplay allows players to check product price tags for fresh local produce, seek advice from a virtual grandmother, or simply choose items based on curiosity, all while navigating the playful environment of the store.

As players embark on their shopping journey, they will encounter various characters, including a neighbor and whimsical creatures like a large crow or a mysterious vent dweller. The game encourages exploration beyond the grocery aisles, leading to experiences such as a rooftop drawing class or an underground snowskate hangout. Ultimately, players will return home to share their shopping experience with grandma, providing a delightful conclusion to their adventure.