Bungie's 1994 science fiction first-person shooter Marathon is heading to iPad.
The port of the Mac game is being handled by indie iOS game developer and Bungie fan Daniel Blezek, who was interviewed on Bungie.net.
The mouse and keyboard controls have been re-jigged. A left thumb virtual joystick controls moving, with the action button tucked underneath.
On the right thumb is primary and secondary fire buttons, with weapon switch buttons at the bottom.
"The original Marathon didn't have an aiming reticule, and by default the iOS version sticks to that, but it can be enabled in the options," Blezek said.
"There is also an option to tap-to-shoot, but two finger tap for secondary fire didn't make it into the final build. Sorry to the lefties out there, a future release will have adjustable controls!"
Blezek used the Marathon source code, released to the open source community in 1999, to build the game.
"Digging into this code base to make the port happen and follow the iOS conventions was a huge effort," he said.
"On top of that, the code depended on a wide range of libraries that also needed to be ported to the iOS. It was months before the code even built without errors."
Still, Blezek's managed to get the game running at a "consistent" 30 frames per second.
The game is still without a release date, or pricing and release details, but Bungie promised to give us all a heads-up once it's ready.
Marathon: Durandal - a bit like Doom but with colour - was ported to Xbox Live Arcade in August 2007. Images of that are below.