Longest development period for a fan-made videogame

Gordon Freeman's original crowbar-swinging antics have been remade anew in Black Mesa – a fan-made remake of Half-Life (Valve, 1998) by the Crowbar Collective. Black Mesa's origins can be traced back to 3 September 2004 when a now defunct website called leakfree.org was created to gather like minded Half-Life fans who wanted to recreate the game using Half-Life 2's Source Engine. That group eventually merged with another group of programmers from the "Half-Life: Source Overhaul Project" to eventually form the Crowbar Collective. The Black Mesa remake (called Black Mesa: Source at the time) was announced on 1 March 2005 – named after the research facility in Half-Life).

On 14 September 2012, an incomplete version of Black Mesa was released as a free download. It contained all of the chapters of the original Half-Life, with the exception of the final Xen stage. Work continued on the game and on 19 November 2018, the Crowbar Collective announced that the missing Xen chapter would finally be released in Q2 of 2019, when the fan-made remake of Half-Life will finally be completed. As of the 6 December 2018 (the date that this record was entered) the Black Mesa remake has been in development for 13 years and 280 days. However, assuming the game is released on 1 April 2019 (the earliest Q2 2019 date) it will have been in development for 14 years and 31 days.