Not being able to foresee my busy week a month ago, the demo won't be ready today. So I've decided instead to release the first level, the second level around Sunday, December 13th and the last, longest and most polished part around Christmas as I will have TONS of free time to make the level nice.
Also, the first level should take anywhere from 5-20 minutes.
You can download the Steam Workshop(See **) version or an archive version (see *). I also have the first composed piece of Before Portal ready, "Extreme Elevator Music". Another, "Classical Science" is being made. Soon they will be able to be listened to. For now, enjoy the first part of the demo.
* How to download and install archived maps:
1. Download archive.
2. Unpack into User/C Drive/Program Files(x86)/Steam/SteamApps/common/Portal 2/portal2/maps/
3. Open your copy of Portal 2.
4. When the menu screen is loaded, press your tilde key. If the console doesn't come up, go to options, Keyboard/Mouse, and turn allow developer console to ENABLE. Now go back to the menu and type "map bp_d_01". The map should load! Happy thinking with portals!
** I'm currently experiencing issues with the Portal 2 Publishing Tool. The map is ready to be released on the workshop, but can't because of this. The Steam Workshop release should be available by December 6th. Thank you for your understanding.