Those that are craving a whole new Portal adventure will probably be interested in Portal: Revolution, a big new mod filled with new puzzles and original voice acting.
We’re probably not going to get another Portal game from Valve any time soon, but thanks to the series’ modding community, there’s basically an entire new entry you can play right now. And as it’s a mod, it’s completely free too! Set between the events of Portal and Portal 2, Portal: Revolution sees you as a new, unnamed test subject who’s tasked by a personality sphere called Stirling to bring Aperture back to “its former glory.”
It’s specifically a mod of Portal 2, meaning it has all of the sequel’s mechanics like the paint that makes surfaces slippery or bouncy. According to the game’s Steam description, “the campaign contains 40 brand new puzzles making use of new test elements and presents existing mechanics in a new way not seen in Portal 2.” New elements include things like a laser cube variant, and a gel cleansing field, though how those work, you’ll have to find out for yourself!