Yesterday, Valve released the last of four Aperture Laboratories promotional videos for the upcoming first-person puzzle title, Portal 2. Once again starring the disembodied voice of Aperture founder Cave Johnson, the video boasts some of the company's advancements in technology.

Sure, Aperture created a "dual portal" device, but Cave is particularly proud of another creation: a specialized set of boots that will ensure the safety of his company's major investments. Citing a "reproducible human error" (i.e. falling to your death), Aperture issues a set of the boots to all of its human subjects.

Chell, Portal 2's returning heroine, shows off her newfound comfort with the boots by flinging herself around the company's new test areas. Of course, we'd expect her to be comfortable with the tech since she sported similar protective gear in Portal 1.

Portal 2 hits stores for the PC, Mac, PS3, and Xbox 360 on April 19; however, there is some speculation that the game will unlock on Steam this Friday as part of the recent "Potato Sack" ARG. Valve recently revealed Portal 2's Steamworks features for the PS3.