First: Push the button.
Push the button. Story related and cannot be missed.



Just keep walking until you push the button. The puzzles along the way are pretty self explanatory but just as a bonus I'll put the solutions for the three rooms below.

Lever room:
Lower all four levers on the centre podium.


Valve room:
Turn three valves as far as they will turn. Turn the fourth valve until the shadow on the centre disk lines up with the black lines.


Keypad room:
You need four numbers to input on the centre podium. These numbers can be found on the surrounding information boards.

The metal keypad. The number 6 is worn away.


The keypad of the future! Enter any four numbers and a combination of asterixes and the number 5 will show on the screen.


The Lightpad information board shows the binary numbers, 0 and 1.

Second
Push it again.


Story related and cannot be missed. Same as First, just keep walking until you push the button.

Third
You had to keep pushing it.


Story related and cannot be missed. Same as First and Second, keep walking until you push the button.

Fourth
Disappointing.


You guessed it. Story related and cannot be missed. You know what to do at this point.

Fifth
You did it!


Story related and cannot be missed. The puzzle answers are a bit different now.

Lever room:
The levers are missing from the centre podium, you can find them around the room.

One is in the plant pot as soon as you enter the room.


Take one off the information board.


Underneath the bench.


Behind one of the information boards.


Valve room:
Same as before, the shadow has to lines up with the black lines. The turn amount on the valves is just slightly different this time.


Keypad room:
The numbers are in the same place as before but two of them have changed.

Lightpad information board. Shows the binary numbers 0 and 1.


The keypad of the future! Enter random numbers, the number shown with the asterixes is now 3.


The metal keypad. The number worn away is 9.

Egress
It's not finished.


When you get to the end door to the left of the button walk through into the white light. When prompted press cancel and you'll be thrown back into the room.

Persistence
It's still not finished.


When you go through the red door and reach another opportunity to end the game through an exit door, walk through towards the white light. Again, when prompted press cancel. You'll be thrown back into the room.

Missives
Read all 3 secrets.


There are three hidden notes throughout the game you have to find. Each one is on a separate "level".

Level 2:
Go through the red door in the keypad room. Go all the way to the end of this section. In the room before you enter the entrance room you started in there is a shelf with a stack of papers on it. The note is amongst them.


Level 3:
When you first start you can enter the white door behind the counter straight away. The note is on the shelves in this room.


Level 5:
In the room with the air duct entrance there is the last note under the stairs.

Rave Mode
Put on a rave.


Find any switch on an information board and use it to switch the light bulb next to it on and off several times until you get this achievement.

Pottery
Destroy all 4 interlopers.


You have to find four gnomes throughout the levels, each gnome is on a separate level. For some reason this doesn't activate for a few people, it hasn't activated for myself despite me playing the game through twice and destroying all four gnomes each time. This is even after a reinstall and all that jazz. I'm not sure why it doesn't work for some of us so if you do know then comment below!

Level 1:
After going through the red door in the keypad room follow the corridor all the way to the end. In the room before the entrance room you started in there are some benches leaning against a wall. Behind them is a gnome. Find the hammer on the shelf and crouch by the benches, press RMB to throw the hammer. Might take a couple of goes but there's plenty of valves and levers in the previous rooms you can use to break it.



Level 2:
This one can be found towards the end of the air ducts. Keep looking up as you're crawling through them and you will find a section you can stand up in. You can find the second gnome here.




Level 3:
This is the easiest gnome to find. Go through the red door in the keypad room. The way to the right is blocked and you can find the gnome here.


Level 4:
This is the hardest one to find because it blends in with everything else. In the corridor before the keypad room, after you have walked past the screen that says "This way to the button", you can find the gnome on the first bench on the left.