This is kind of old news that I only caught up on recently. Since October, Momentum Mod now has a publicly playable playtest, announced alonside their 0.10 update. I’ve been waiting to try this game out since I first heard it mentioned in a related project, Portal 2: Community Edition.
Momentum Mod is a standalone game aiming to be pretty much the greatest hits album of advanced Source Engine movement. It has game modes for the major categories, like rocket jumping, surfing, and bunnyhopping. It also has built-in speedrunning and practice tools, like automated timers and a meter that shows how well you’re airstrafing.
It uses a highly modernized version of Source, now branded as Strata Source. Strata is also powering Portal Revolution and Portal 2: Community Edition.
For some visual interest, here’s an embarrassing clip of me messing up in a beginner-level surf map.