Half-Life: Lemmings is a mod for Half-Life: Source that allows players to rescue up to 45 non-playable characters (NPCs), such as scientists and guards, within the Black Mesa facility. The mod features custom animations for rescuing NPCs, enhanced navigation capabilities for them, and upgrades for guards who can now use shotguns, MP5s, and grenades. The mod covers gameplay from the beginning of the Unforeseen Consequences chapter to the Apprehension chapter. It is available for download on ModDB, although Half-Life: Source is not listed on the Steam store but can still be purchased for £8.50.