Lifeline takes advantage of your smartphone or tablet and simulates a real-time communication from an astronaut named Taylor, who crash-landed on an unknown moon and managed to establish communications with the player. The whole game takes place via incoming text messages from Taylor and binary player responses which direct the astronaut to a next goal (which way to go, when to eat food etc). The communication takes place in real time, meaning for example Taylor might decide to go to a distant peak (or get sent to by the player) and take several real time hours to report what was found at the destination or along the way. This restriction is not too harsh, if the player does not respond to incoming messages, the game halts and waits for input. The game takes several days to complete. There are many branches of the story that get Taylor killed, but it is possible to rewind the story back to any branching point to continue with an alternative path. After the game is completed twice (including endings which kill Taylor) a "Fast Mode" can be turned on, which removes the real time dependency and allows for a much quicker story progression.