A new Portal game is out, but it’s not the sequel you might be hoping for. And no, you’re not the first person to note it’s a case of Valve being allergic to 3.

The game’s title of Bridge Constructor Portal functionally explains which two games it has merged, and it’s one of those partnerships that seems obvious when you see it. The actual meat of the gameplay is from Bridge Constructor, which involves using physic puzzles to build bridges in unusual situations and then test whether they can bear the load.

Portal brings two elements to the party. Firstly you get the visuals and the GLaDOS character as narrator, complete with original voice artist Ellen McLain and a series of insider references to the Portal ‘universe’. Secondly, some of the tools from the game such as cubes, propulsion gel and those pesky sentry turrets have been incorporated into the game.

Early reviews suggest the developers have done a great job of using these to add to the challenge and overcoming the initial problem that using portals would seem to be a very simple way to avoid needing to make a bridge in the first place.

It’s your usual mobile game format of 60 sequential levels, each unlocking the next. For those who like high scores, you get a “wasted infrastructure cost” for each level (in other words, how far you were from the most efficient bridge design). You also have the option to try putting multiple vehicles over the bridge, rather than just the one forklift that’s needed to complete the level.

The game is out today on iOS, Android, Linux, Mac and Windows, with console versions due out next year.