TWHL Tower: Source is the follow-up to the collaborative mods TWHL Tower and TWHL Tower 2. Each level is made by a different creator with the only limit being the size of the map. Other than that, every floor has unique and varied gameplay ranging from puzzles and platforming to intense combat sections. TWHL Tower: Source expands on the previous mods by using Half-Life 2's Source engine together with the community made Mapbase mod to allow for even more unique gameplay possibilities. The mod features 18 floors by 15 different authors, 5 unlockable bonus maps, and over 20 in-game achievements for those seeking extra challenge.