Accelerated Back Hopping
Accelerated Back Hopping (ABH for short) is a Glitch, and it's the main method of transportation on OrangeBox Engine-based games. ABH replaces Bunnyhopping, which was fixed in the OrangeBox Engine. It is also significantly faster than bunnyhopping.
To ABH you need to face the opposite direction of where you are about to go, then jump backwards, hold the duck key and continue jumping as you hit the ground. You need to release your directional keys while ABH-ing in order to maintain and increase your speed. You can make turns by changing the direction where you are facing and pressing a certain strafe key. Binding jump to mouse wheel or using a jumping script is recommended as it makes timing jumps a lot easier.
You can also jump forward, then while in the air quickly turn around and continue ABH-ing.
When you exceed the game's speed limit, the game tries to slows you down whenever you jump, back to the desired speed. By default the game thinks that you're moving forwards, so when you exceed the speed limit, it'll accelerate you backwards. If you are facing backwards, this will only increase your speed. So, the faster you're going - the more you will get accelerated. The speed limit varies: it's 209 UPS(hammer units per second) while crouched, 225 while walking, 285 while running and 350 while sprinting. This is why it's generally recommended to crouch while ABH-ing.
There are some ways to gain speed similar to ABH:
- Accelerated Forward Hopping (AFH)
- When you gained some speed while ABH-ing, you can turn around and hold S. This way the game thinks that you are traveling backwards and so it will try to decelerate you by applying force the direction you are facing, so you still gain speed. But it is not as fast as ABH because when you are holding S, you are slowing down due to airstrafing. So when you AFH it is best to hold S only when you hit the ground and jump. This is not true in Portal, you can hold S the entire time without much penalty because of the lessened air control.
- Accelerated Side Hopping (ASH)
- You can also ABH sideways. To do that you need to jump, turn your mouse a bit to the side and then hold S + strafe key opposite to the direction that you turned your mouse to (if you turned your mouse to the left, you'll need to hold S + D, to the right - S + A).