Vent Glitch: How to quickly skip the early game

This is not my own discovery and has been long known. I am just putting it into guide format for easy access here on Steam. You utilize the vent in B1 of the first building to skip the game from just before the DARPA Chief to the part where Snake has been captured and is in a cell. Story-wise, it's after Snake has been captured by Sniper Wolf, so the next thing to do is proceed from the first Sniper Wolf fight area to the stairwell fight in Communications Tower A.

Instructions

Step 1

Get to floor B1 of the first building, on your way to the DARPA Chief early in the game.

Step 2

Go to the south-east area near the ladder you would normally climb up, and look for a vent in the floor to crawl into. Reverse Snake into this vent (feet first) until he's in about to his waist (shown below). You essentially want Snake to be backed in as far as he can go without it automatically entering first-person view on you.

Step 3

Enter first-person view with triangle (or Y button), and then look up at the ceiling in first-person view.

Step 4

While looking up at the ceiling in first-person view, let go of all buttons, and then QUICKLY hit the X button (or A button) to stand up. Snake should be standing inside the wall as shown here.

Step 5

From here on out you are outside the games walls, it's best to use your dot position on the Soliton Radar and first-person view to run around. We need to get from this east side of the map to the west side of the map. Enjoy the sights along your journey.

First head north, as shown on this Soliton Radar.

Step 6

Then head west around the elevator.

Step 7

Then enter from the left side along this wall path shown here, and head west until you hit the dead-end in the walls that shows on the radar here.

Step 8

Go up, then left to about here as shown on the Soliton radar in the screenshot near the door you would normally exit when you escape from Torture.

Step 9

Then you need to go around and physically hit the door even though you can't see yourself. Run out to the left, then up, then right and into the door from the left side. See path shown on radar here.

Comments about this

If all done correctly, congratulations, the screen will go black, and it'll load the scene of Snake first waking up in the cell that normally happens after the first Torture scene. Since that was skipped, then the first time Johnny says you have to go back to be tortured, you will still get that first torture scene you had missed, even though normally this would be your second trip to torture.

Health
Some important things to note. If you did this, then you skipped a lot of the game that would have occurred in regular sequence. This means you will initially have very low health. Not to worry though, if you go re-enter specific rooms in the game where boss fights would have occurred, an animation of Snake gaining health post-boss fight will trigger on most of them.

I know this works on crossing the snow field, you will see a destroyed tank here that you didn't destroy (first Vulcan fight skipped), and upon entering the nuke building, you'll get a health bump and a Codec call that occurs out of sequence about the nuke building. You'll also get a health bump upon entering the Commander's room (Psycho Mantis fight). The door won't visually be open, but you can walk through it in order to continue to the caverns where the husky-wolves are, and through to the first Sniper Wolf fight that didn't happen where Meryl didn't get captured because you skipped it.Then you can proceed through the door at the end to get to the stairwell fight and continue the game.

Items
Note that this also means you will be low on items in the game. It's a good idea to call Otacon from the cell (Codec 141.12) and have him visit you to give you the level 6 card. You may also want to consider backtracking a bit and scavenging for things you didn't grab beforehand. The game is very out sequence now as a result of this. Have fun with it.