About Goldsrc Bhop
Goldsrc Bhop is a direct port of Half-Life 1 grounded and aerial movement physics into Sandbox. This features auto-bhop (hold space to jump), a speedometer, and a timer HUD. This hud functions in any map containing the added hammer entity TimerManager. Attach a button entity's output to the StartTimer input method, and another to the StopTimer input method, to make full use of the timer.
When creating a lobby, toggle the map filter that limits your selections to maps tagged with "bhop" by clicking the "Bhop Maps" text above the map name (If it says "All Maps", click it again to filter for bhop maps).
Use keys 1-5 while in game to utilize checkpoints, start the timer manually, and reset your position to the start of a map. This should make it possible to play maps without my hammer entities incorporated.