Remember QPong for Quake2? This is a start at recreating it. It's simple: A long map, 2 goals and an eight foot ball. Shoot the ball into the enemy's goal. Some weapons work better than others. Be careful though, getting too close to the ball can seriously damage your health! Currently the game registers goals and keeps score, and is one of the few HL2 mods to have a Linux server.
This is ps_displace.
Unfortunately you cannot see barrels and weapons from this height.
don't use displacements if they're not necessary