Blendo Games has publicly released the source code of its latest game, Skin Deep, encouraging other developers to build more stealth games in its footsteps—or at least to take a look at the sick game engine it built. I, for one, am shocked by a specific thing about it: It runs on a core of idTech4, which you may recognize as the engine behind Doom 3.
"The original idTech4 was made in 2004, so we had to implement a lot of things that were now expected in a modern 2025 game. It was a lot of work!," said Blendo on its blog. "Gameplay in Skin Deep is quite different from Doom 3, so the gameplay code likewise has a large amount of additions and changes."
The code release, on GitHub, hands out the keys to the tech underlying Skin Deep. "This basically means you are free to use the source code for personal or commercial purposes, with the caveat that you publicly release any source code changes you make," said Blendo. (Noting also that this doesn't make the game itself open source, especially stuff like its art, models, textures, audio, and levels.)
Releasing a heavily-worked-on engine into open source is a pretty in-character choice for Blendo Games, an open early proponent of the indie games scene and a popular developer since the release of 2011's Atom Zombie Smasher. Still, it's a huge gift to others looking to create similar games or deepen their knowledge of how games are made.
Blendo also released a big pack of example maps for those looking to mod Skin Deep this week. Each map is designed to demonstrate how a specific thing in Skin Deep works for those who'd like to make their own maps or just understand how the game mechanics work at a technical level. This is in addition to their earlier mod museum, a map that shows you how Skin Deep works behind the scenes.
You can find Skin Deep on Steam, where it's normally $20 but is currently 20% off for the Steam Summer Sale.
