The story of 'Duke Nukem Forever' is one of the most infamous in gaming history, with the game finally being released in 2011 to poor reviews after a 13-year delay.
The game went through many different iterations and shifts in art style, but a modder has unearthed a build of the game that was shown at E3 in 2001.
The leaked gameplay appears more fluid and complete than the finished product, with an arsenal of weapons available to play with (as opposed to the 2 fixed weapon slots in the finished game) the EGO meter was more of a core part of gameplay, and levels were more interactive.
Leaking on 4chan, user x0r has detailed their findings on the thread, stating that they aim to make the source code available as soon as June so fans can enjoy a different iteration of the game.
x0r said that "almost every chapter is present in some form. A huge chunk is playable, a huge chunk is block-outs with no enemies, and all of the E3 content is there."
x0r claims they will release the level editor along with the source code, and that all the weapons in the game are fully functional apart from the chainsaw and freezer.
Series creator George Broussard verified that the leak appeared to be real, but added that fans should "heavily tamper expectations."
It is worth noting the leak is not the finished game, and indeed is only a rough build of a game that was eventually released 10 years later.
'Duke Nukem Forever' has perhaps the most tortured production process in gaming history, and the final results were not worth the wait by all accounts.
Released in June 2011 to poor reviews, the game was trashed by critics for feeling distinctly out of place in the landscape of first-person shooters of the era.
The game was poorly optimised for the PlayStation 3 and Xbox 360, with particular umbrage taken with the games long loading times, poor graphics, tedious gameplay, and most controversially among 'Duke Nukem' fans, only two weapon slots for the gun-toting hero to carry.
Fan site Duke4.net has the full scoop, including videos of the build, which shows fans a glimpse into an alternate universe where 'Duke Nukem Forever' was good.