You leap down into the tunnel, pausing only to check with your fingers that the surface is indeed perfectly smooth, like glass. You head to the left for a few metres, and reach the other exit. It is about a metre up the wall, not normally a difficult climb, but your boots refuse to find purchase on the sloping side.
You take a couple of tries, and are then rather worried to hear the sound of the approaching fireball from the left.
Knowing you need to act, and now, you brace yourself, and then quickly run towards the opposite wall. Even as you begin to slide, you turn and head the other way. The momentum of your short downhill run propels you marginally more successfully up the other side, but it is just enough to grab hold of the small tunnel and pull your upper body inside.
The sound of the fireball grows louder, and you know it must be almost on top of you. Stretching forwards, you put all your energy into one pull, and your body shoots into the tunnel, even as the white fire passes behind, just catching the tips of your boots as they move.
Taking a moment to recover from the sudden exertion, you find yourself lying on your belly in a dusty, dark and low tunnel.