Sweet Half-Life speedrun done at 25:03 by Zhouy and Dark_Devil aka rayv3x.

Tricks description:

00:07
Dark_Devil gets boost from gauss and uses the edge as ramp to get over the fence.
APPROX SAVETIME: 0:40 minute(s)

00:15
Dark_Devil gets boost from gauss and uses the edge as ramp to get up to the button.
APPROX SAVETIME: 0:25 minute(s)

00:49
Zhouy makes a nade boost to get up to the vent faster. The gravity trigger there prevents him from falling down again.
APPROX SAVETIME: 0:50 minute(s)

01:32
Dark_Devil reaches the time-trigger for the next fight scene and gains enough speed to jump through the door before it
closes. This way he is able to collect the rest of the items lying around in the tunnels. Also hes able to finish the map
faster as he can gauss boost straight to the end and doesn't have to kill all the marines first and get out of the room.
APPROX SAVETIME: 1:00 minute(s)

04:54
Dark_Devil throws grenade to activate the cube immediately after its spawn.
APPROX SAVETIME: 0:02 minute(s)

04:05
Gonarch got certain waypoints and can only be hurt everytime he reaches a waypoint, shooting him between the waypoints is absolutely pointless as he won't take any damage.
APPROX SAVETIME: -

07:10
Dark_Devil shoots RPG before corner to directly steer it onto the terminal as soon as possible to open the door faster.
APPROX SAVETIME: 0:04 minute(s)

08:28
Dark_Devil jumps off the elevator to reach the exit earlier.
APPROX SAVETIME: 0:05 minute(s)

08:56
Dark_Devil gets boost from gauss and uses the cursive edge as ramp to get up to the higher stage.
APPROX SAVETIME: 0:20 minute(s)