Question: What game did the writer of "Blackmoor" help co-develop?

Context paragraphs:
Karaoke Joysound: Karaoke Joysound Wii (カラオケJOYSOUND Wii) is a karaoke video game by Hudson Soft for Wii.  It licenses the "Joysound" online song library from Japanese karaoke service provider Xing, who also helped co-develop the game with Hudson.  The game was originally released in a retail package with an included USB microphone on December 18, 2008 in Japan, and was later released there as a downloadable WiiWare game on July 28, 2009.

2K Marin: 2K Marin, Inc. was an American video game developer based in Novato, Marin County, California, United States.  The studio's main focus according to press releases is to develop new intellectual property and co-develop products with other 2K studios.

Greyhawk: Greyhawk, also known as the World of Greyhawk, is a fictional world designed as a campaign setting for the "Dungeons & Dragons" fantasy roleplaying game.  Although not the first campaign world developed for "Dungeons & Dragons"—Dave Arneson's "Blackmoor" campaign predated it by over a year — the world of Greyhawk was the setting most closely identified with the development of the game from 1972 until 2008.  The world itself started as a simple dungeon under a castle designed by Gary Gygax for the amusement of his children and friends, but it rapidly expanded to include not only a complex multi-layered dungeon environment, but also the nearby city of Greyhawk, and eventually an entire world.  In addition to the campaign world, which was published in several editions over twenty years, Greyhawk was also used as the setting for many adventures published in support of the game, as well as for RPGA's massively shared "Living Greyhawk" campaign from 2000–2008.

Blackmoor (supplement): Blackmoor is a supplementary rulebook (product designation TSR 2004) of the original edition of the "Dungeons & Dragons" fantasy role-playing game written by Dave Arneson (with a foreword by Gary Gygax).

Mountain Sheep: Mountain Sheep Oy, internationally doing business as Mountain Sheep, Inc., is a Finnish independent video game developer based in Helsinki, Finland.  Founded on 13 April 2006, the company is best known for developing "Minigore".  On 29 March 2010, Mountain Sheep opened a second studio, Cornfox & Brothers Oy (internationally doing business as Cornfox & Brothers Ltd.), to co-develop "Death Rally".

Blackmoor (campaign setting): Blackmoor is a fantasy role-playing game campaign setting generally associated with the game "Dungeons & Dragons".  It originated in the early 1970s as the personal setting of Dave Arneson, the co-creator of "Dungeons & Dragons", first as a setting for Arneson's miniature wargames, then as an early testing ground for what would become "D&D".

2K Australia: 2K Australia Pty Ltd was an Australian video game developer based in Canberra, Australia.  The studio was founded in 2000 as Irrational Games Australia Pty Ltd with Jonathan Chey taking the helm, and in 2007 they changed their name to 2K Australia.  The studio's main focus according to press releases was to develop new intellectual property and co-develop products with other 2K studios.

Nancy Drew: Curse of Blackmoor Manor: Curse of Blackmoor Manor is the 11th game in the Nancy Drew point-and-click adventure game series by Her Interactive.  The game is available for play on Microsoft Windows platforms as well as on DVD, Steam, and GOG.com released a digital version on their site.  It has an ESRB rating of E for moments of mild violence and peril.  Players take on the first-person view of fictional amateur sleuth Nancy Drew and must solve the mystery through interrogation of suspects, solving puzzles, and discovering clues.  There are two levels of gameplay, Junior and Senior detective modes, each offering a different difficulty level of puzzles and hints, however neither of these changes affect the actual plot of the game.  The game is loosely based on a book entitled "The Bluebeard Room" (1985).

Dave Arneson: David Lance "Dave" Arneson (October 1, 1947 – April 7, 2009) was an American game designer best known for co-developing the first published role-playing game (RPG), "Dungeons & Dragons", with Gary Gygax, in the early 1970s.  Arneson's early work was fundamental to the development of the genre, developing the concept of the RPG using devices now considered to be archetypical, such as adventuring in "dungeons" and using a neutral judge who doubles as the voice and consciousness of all other characters to develop the storyline.

Divekick: Divekick is a 2D competitive fighting game originally developed by One True Game Studios, an independent collective made up of a group of competitive gamers.  A demo of the game was showcased at several competitive events, and after a positive reaction, the group created a Kickstarter campaign to fund the creation of a full version for release on Microsoft Windows.  The Kickstarter project was canceled after it was announced that developer Iron Galaxy Studios had agreed to co-develop and release the game.  The name "Divekick" is a reference to a common mechanic in many fighting games (particularly those created by Capcom) in which some characters can jump in the air and do a diving kick with a sudden increase in momentum.  In fighting games, dive kicks are usually very powerful, abusable tactics.  The gameplay in "Divekick" revolves entirely around this mechanic.  The game was released for PlayStation 3, PlayStation Vita, and Microsoft Windows via Steam Greenlight on August 20, 2013 in English-speaking regions.  The game was released in Japan on September 17, 2014.  A major balance update to the game, titled Divekick: Addition Edition, was released in April 2014, and a port of the game for PlayStation 4 and Xbox One, titled Divekick: Addition Edition +, was released on October 7, 2014.

Supporting paragraphs: Blackmoor (supplement) Dave Arneson
Answer: Dungeons & Dragons