The rock glitch allows you to grab a rock before the game even starts, getting a 0.001s time.

The rock glitch happens because the game actually starts running on the "ready" loading screen, but right as the game is going to start it resets your position. With that said, you can do simple actions while in this glitched state, such as picking a rock.

In order to do the glitch, you have to do the following:

1. Spawn in front of a rock, for set seed a good seed for this is "1", for random seed it's estimated to have a 1/300 chance to occur.
2. As the "ready" loading screen appears, point your mouse cursor down.
3. Spam "e"

If the glitch works you will hear the item grab sound effect, and when the fade-in happens you will already have a rock on your inventory!

P.S.: There is a way of doing the glitch without moving the mouse at all called the rock glitch variation, but it requires a setup before the run and is banned in all categories except for Collect Rock Set Seed (the reason being that for this category specifically it gives no advantage compared to the regular rock glitch)