Veteran members of legendary developer id Software last night celebrated the 20th birthday of its first game: Commander Keen.
The side-scrolling Super Mario-esque PC game is the earliest work produced by the id team, predating first-person shooter classics Doom and Quake.
It launched on 14th December 1990, two months before the company was officially founded.
To mark the series' 20th anniversary, developers from id Software and Bethesda shared their memories of the game on the Bethesda Blog.
"My childhood was pretty much made up of Mario games on the console, and Commander Keen on the PC," recounted id Software's Mike Rubits.
"I was only three years old when the game was originally released, but I still must have played the first level in each game hundreds of times, not being talented enough to get much further. I didn't even realise until well after DOOM that the same people were responsible for both games; I just knew that I spent far too much time on both."
id's Shawn Casey offered this: "I remember always being jealous of the NES crowd because they had a cool platformer, and it wasn't until Commander Keen came out that I could finally enjoy my own platformer on the PC. Playing it with the Gravis gamepad was a blast, even with a snapped off stick."
Commander Keen put the player in the shoes of Billy Blaze, an eight-year-old boy who travels through space and assumes the identity "Commander Keen". It was designed by Tom Hall, who went on to co-found Ion Storm with John Romero, and was programmed by John Carmack.