The game is a 2D top-down puzzle inspired by superposition of quantum states. Similar to Schrödinger's cat, the main character, the little girl, is simultaneously alive and dead due to a hospital medical accident. The alive state little girl and the dead state little girl are in two different world. Once observed, superposition collapse into one of the possible definite states, meaning that one of these girl will be disappeared. To ensure each other's presence, they need to work collaboratively to escape the hospital without being observed by anyone.

Players need to switch between different worlds and control two  characters simultaneously to solve puzzles. The flashlight can be used to remove obstacles in other worlds to help each other to get through different levels. The game is also an open-world Metroidvania experience where players can explore different rooms non-linearly, backtrack previous levels, collect souls, and upgrades for gaining access to different areas.