'Unlike anything you've ever played': Immortality, the video game that's actually three movies

Every now and then you play a video game that you just cannot stop thinking about. Candy Crush might leave colourful imprints on the back of your eyelids. And then, very occasionally, a game comes along that is so entirely unlike anything you've ever played that it becomes an obsession. Immortality, the latest from lauded game-maker Sam Barlow and his studio Half Mermaid, is one of those. It is something that has never existed before: a video game that is also three feature-length films, wrapped around a mystery so compelling that I couldn't concentrate on anything else for days. It is so delicate and complex that it's difficult to figure out how it even works.