1. SDL: 1.2.10
2. SDL_mixer: 1.2.6
3. OpenGL: the best is to have OpenGL 1.3; if your OpenGL driver is in earlier version check if it has the folowing extensions:
* OGL 1.0 - you can't run the Citadel with this version of OpenGL!
* OGL 1.1 - with this version you need GL_EXT_bgra, GL_ARB_multitexture, GL_ARB_texture_env_add and GL_ARB_texture_env_combine extensions
* OGL 1.2 - GL_ARB_multitexture, GL_ARB_texture_env_add and GL_ARB_texture_env_combine extensions
* OGL 1.3 and above - no additional extensions needed
4. GLU: should work even with 1.0 but I only tried 1.3

The slowest hardware configuration on which the Citadel was tested and worked is:

* 333 MHz Intel Celeron A processor
* 96 MB of SDRAM memory
* Matrox Millenium G400 graphics card with 16 MB of video memory
* ISA sound card

About 15 MB of hard disk space is required. The current version should work with 16 MB of system memory and 8 MB of video memory.