Greenhouse Interactive, which was founded six months ago as an online store for independent game publishers, has released a free SDK (software development kit) that allows developers to insert social networking functionality in their games. Dubbed Nitrogen, the toolset gives designers a way to reward players for in-game accomplishments and display those achievements to others.

The company calls the functionalities "triumphs" and "standings," leading representative Vlad Ceraldi to quip in a press release: "In a crowded gaming world of achievements and trophies, itis inevitable that all of the good words are gone. Weive just snatched the last few that make any sense, so igood lucki to anyone else looking to offer something similar."

Colleague Robert Khoo added: "To the best of our knowledge, this is the first time anyoneis offered these kinds of in-game reward and integrated community features on the Mac and Linux platforms. In fact, triumphs and standings are only the beginning. Thereis so much more in the works with Nitrogen that we just havenit found the vocabulary for yet. Stay tuned."

Ceraldi also serves as CEO of Hothead Games, developer of the On the Rain-Slick Precipice of Darkness series co-created with popular online comic strip Penny Arcade. Episode two in the series launches on Wednesday for Mac, Linux, and Windows. It will be the first game to feature Nitrogen functionality.

Nitrogen isnit available for download on the Greenhouse web site, but developers interested in obtaining a copy should contact business development manager Gregan Dunn.