TL;DR of the article, generated automatically.

Tactical-Retreat is a free, multi-platform Counter-Strike v1.5 port written in QuakeC, with a 2026-06-03 release for Linux and Windows.

• What it is: Formerly known as FreeCS and OpenCS, it runs on the FTE QuakeWorld engine and is built on the Nuclide project. The site says it has been tested on Linux, OpenBSD, and Windows.
• Getting it running: The site offers a one-line install script. Otherwise you extract the release archive and, if you lack the game data, use REWise to pull the content from csv15full.exe. You don't need to own Half-Life or Counter-Strike, though some custom maps that rely on custom Half-Life content may not work.
• Building it yourself: You need git, then clone Nuclide and the cstrike and valve repositories, and run `make game GAME=cstrike`.
• Features: Weapons, items, and NPCs are defined in decl files rather than code, with weapon prediction, bundled bots, voting, and a metamod-style plugin system. The code is under the ISC License.