To import a Portal bonus map in Windows,
- Download puzzle_box.bmz.
- Launch Portal.
- Go to "Bonus Maps" and then "Import Bonus Maps..."; navigate to and select puzzle_box.bmz.
- A folder titled maps/puzzle_box will appear in the Bonus Maps window; open it, and then select the
map puzzle_box, and it will load.
To import a Portal bonus map on a Mac,
- Download puzzle_box.bsp.
- Put it in the following directory: ~/Library/Application Support/Steam/SteamApps/<yourusername>/portal/portal/maps/.
- Launch Portal.
- Click on Options, then Keyboard, then Advanced, and then enable the developer console.
- Hit the ~ (tilde) key to open the developer console.
- Type 'map puzzle_box' to launch the map.
(NOTE: Due to an inadvertent error, the word "mysticeti" is misspelled as "mysteceti" in this puzzle.
This is not a clue, merely an error, for which we apologize.)