What is Surf? #
Surf is a very popular gamemode in which a player slides down a ramp to gain speed.
History of Surf #
3kliksphilip has created an excellent video going over the history of Surf with Mariowned, the creator of the gamemode:
How Surf Works #
In Source, a player can only stand on a angled surface if it is less than 45.573° from the horizontal. If the slope is greater than this, the player slides down it. However, if the player holds the direction key pointing into the slope, they can stall themselves from falling and remain “airborne” without actually moving downwards. This can be exploited by increasing the air acceleration value to allow the player to convert their downwards speed into horizontal speed, and their horizontal speed into upwards speed.
The player holds the strafe key pointing towards the highest point of the ramp and keeps thier crosshair so that the direction of their view is parallel to the ramp (sliding along it). From there the player can move their cursor inwards (towards the peak) or outwards (away from the peak) to exchange their speed for height and vice versa. If turning, air-strafing usually takes priority over sticking to the ramp, so the player may have to switch which direction key you’re pressing away from the peak if on the inside of a curve.