Portal has inspired a lot of similar games over the last decade or so that have tried to emulate and improve the formula, but none have really managed it except for the sequel, Portal 2. The Turing Test from Bulkhead Interactive is another title that’s even more similar than most. You have a robot narrator called T.O.M in the same vein as GLaDoS and you progress through sectors as opposed to chambers but their function is identical. The majority of the game is contained inside an enormous facility with the inspiration being clear for everyone to see, but it’s a tough ask to be a better game than what many consider to be one of the best games of all time.
Thematically, Portal is undoubtedly the main inspiration. To describe the game more effectively however, it’s like Portal meets 2001: A Space Odyssey, with Alan Turing’s famous test being the concept built upon. For those unaware, the Turing test in real life is “a test for intelligence in a computer, requiring that a human being should be unable to distinguish the machine from another human being by using the replies to questions put to both.” So it’s pretty easy to predict and understand the direction the story takes overall after the first hour or so, though there’s still a lot to discover and unravel.