

Texture this brush with tools/toolsskybox. Next, create a brush where you want the skybox to be naturally, make sure it seals the map from leaks, as always. Then, make a second ceiling for the skybox (NB the ceiling isn't 100% open it is partially closed around the edges), and fill it with more debris (hanging vegetation, rusty beams, cables, etc.). Now make a big hole in the ceiling, and detail it with rusty frames and foliage props. Next, find the key value that says what the skybox texture should be, and change this to sky_white - no folder, no file extension, just that. Go into the Map menu and select map properties. Skybox lighting is actually very easy to create.

Since the theme is supposed to give the impression the player is very close to the surface, certainly the sun shines on the test track. If you'd like to let the player see the puzzle, adding a light source is very important. The sky you're looking for is simply sky_white. The destroyed theme is characterized by the very organic feel of it the vegetation is the most iconic element of the theme, while the skybox is the main source of light in the map. If you have a new testing element to show off, this sort of striking theme might just ingrain it in the player's mind forever. As stated above, this theme is designed to leave an impact on the player so if you have simple yet innovative and unique puzzles, or those with brilliant moments of epiphany (colloquially known as 'aha' moments), use this theme. However, don't limit yourself to such simple tests.

Tutorials - simple cube- and button-based testing and portalling/momentum puzzles.

The official campaign uses the theme only for two things: On that note, however, do not confuse this with being dynamic the player must get the feeling that everything is dying, if not already dead, that this is the end, and that they are in solitude. This theme is supposed to give the effect that everything feels very organic. In the single-player campaign this was the first theme the player had encountered, and consequently had been designed to be visually striking and to leave as big an impact as possible on the player. Earlier tests in Portal 2 use this theme to make even a small test unforgettable.
