Source

Background
Source is a 3D game engine developed by Valve as the successor to their original GoldSrc engine, introduced in June 2004. Source does not have a concise version numbering scheme; instead, it is designed in constant incremental updates. It is named after Half-Life: Source, the first game by the corporation to utilize the engine.

(June 1, 2004-)
Logo: After the Valve logo, we see the words "powered by" on top of "source" in white, with an symbol resembling a part of the Half-Life 2 logo surrounding the "e" and copyright notice below.

Variants: On console versions of Half-Life 2, the logo does not have a copyright notice.

FX/SFX: None.

Music/Sounds: None.

Availability: Common. Appeared on all games by Valve since Half-Life: Source.

Editor's Note: A well-remembered logo for fans of Half-Life and Portal.