Devolver Digital has released several prototypes for free on Steam, going back as far as 1993 for the original Shadow Warrior.
The earliest prototype, running a Wolf3D-style engine.
The first prototype using the Build engine. The game requires you to specify a map before launching - two which are present in this prototype. Runs v4 of the Build engine.
This version introduces video sourced graphics for the players hands and active weapon. This version comes with four maps and runs v6 of the Build engine
This is the last prototype before development moved in-house. It is also the first to have a working title screen, and to run v7 of the Build engine.
Most of the video-sourced graphics are gone, with only the Katana remaining from previous prototypes. The Riot Gun, Rocket Launcher, Grenade Launcher and Sticky Bombs are introduced.
The Katana now has new graphics. The Rail Gun is introduced.
Much of the final game's graphics are now present.