Cube (Portal 2) - Valve Developer Community

Why in Portal with RTX Companion Cube looks just like in original

Portal 1 cube replacement for Portal 2 file - ModDB

Portal - Tutorial - Box Dropper - Valve Developer Community

Portal 2 Puzzle Maker: Cubes - Valve Developer Community

Portal 2 Gets a Valve-Approved Fan-Made Prequel Mod This January

Portal writer says people at Valve like his pretty awesome idea

Cube (Portal 2) - Valve Developer Community

Dropper (Portal 2) - Valve Developer Community

Portal 2 - Valve Developer Community

Steam's top-rated game sees free prequel delayed as Valve reviews it