This is adequately described and it's difficult to add more without spoilers. But this is based on a 2009 video game, more specifically, a type of "point and click" adventure that's called a Visual Novel. Obviously, in the game you can make different choices, but the film is a linear narrative, so the experience can't really compare. It's a well-done adaptation I think, but I understand why perhaps to people who played the game it might seem simplistic. There just isn't the ability to have alternate endings, or alternate endings. Another anime adaptation was made in 2018 of Steins;Gate 0, the sequel to the original Steins;Gate game, premiered in 2018.