Just a quick video of me testing the vent generation system.

Left-clicking a vent entrance on the ground enters the vent, left-clicking it in the vent exits. Right-clicking the entrance when in the vent peeks outside of the vent.

Eventually you'll need to have something in front of the entrance to climb up, and climbing down without something there stands a chance of breaking your leg.
I must say, the moment I saw this video, I instantly want to play the game, and I'm on the "inside" of the project.

I cannot WAIT to play.