Open source game engine version developed by Croteam for Serious Sam Classic with Vulkan support (Windows, Linux, FreeBSD, OpenBSD, macOS, Raspberry Pi OS). Based on https://github.com/sultim-t/Serious-Engine-Vk and linux port https://github.com/icculus/Serious-Engine
http://www.cngwireless.net/ - is down: https://downforeveryoneorjustme.com/cngwireless.net?www=1
So, it's better to use same archive.org for demos and patches.