Clean (Portal 2)
From Valve Developer Community
This Portal 2 aesthetic theme is shown in the later stages of the single player campaign, in deeper Aperture Laboratories chambers. It is characterized by cleanliness and order. The lighting is mostly cold, thanks to glass lights, although some warm light strips may be present.
This theme is also used throughout most of co-op, in particular Courses 1 and 2. However, this theme is also used throughout the single-player campaign, mostly during Chapter 4 and the first few test chambers of Chapter 8 (the rest of them are Wheatley-themed).
Level transitions are placed in pristine elevator rooms.
Elements

An example of a clean test chamber, from Portal 2 Singleplayer mode.
- Light Strips, not broken nor flickering
- Turbine Entrance and Exit Elevators
- Test Chamber Doors, not malfunctioning
- Observation Rooms with lights on, not flickering
- Test Chamber Sign, not flashing
- Panels
- Any other testing elements