Starsiege: Tribes is even closer to line rider in spirit. It came out just before Quake 3. It has massive (many km^2) outdoor maps with rolling hills and jetpac

Starsiege: Tribes is even closer to line rider in spirit. It came out just before Quake 3. It has massive (many km^2) outdoor maps with rolling hills and jetpacks. Early in the alpha the devs and the users figured out that by spamming jump while going down a hill you could "ski" and pick up speed the jet up the next hill to maintain. This bug, skiing, became the central element of the game. And because Tribes allowed client side scripting in a c++ like language you could just use a "jump script" to efficiently ski. Eventually people were building line-rider style FPS maps for skiing starting around 1999.