35MM is a survival game set in post-apocalyptic Russia, where most of humanity has died to a global epidemic. You play as one of two travellers, as they explore the ruins of humanity to find resources and survive.
Along their journeys, they'll navigate fields, forests, and even a secret underground facility. A lot of the game is a walking simulator as the pair walk along, occasionally picking up food and other supplies to keep themselves going. This is interspersed occasional sections of other gameplay, such as puzzles and shooting.
Heading of the beaten path can sometimes reward you with notes giving more details on what happened to humanity in the events taking place before 35MM. Completing certain requirements will also allow you to access a number of different endings once your journey is over.