Hey,

There are 10 achievements. You get 1 while in the main menu, and only 2 are unmissable. All 10 can be unlocked in a single playthrough, which shouldn't take you much longer than an hour or so.

Timestamps:

0:27 = Stay Sharp (Get the axe)
1:45 = Judo Chop! (Instakill an enemy)
2:28 = Did I Flush? (Enter one restroom twice)

3:58 = Now We're Talking (Get the pistol)
8:13 = Spit-Take (Kill the 3-faced abomination)
9:49 = Paradoxical Plumbing (Blow the same pipe twice)

13:02 = Marked (Backtracking/finding the pages achievement)
17:31 = That Looked Like It Hurt (Hit the big bad boss in the face)
18:28 = Defeating the Boss

> Looper - Take your time looking at the menu, resulting in a screen loop.
Stay on the main menu until the background scene completes a full rotation.



> Stay Sharp - Get the axe
Can't be missed.


> Judo Chop! - Instakill an enemy
This can be done on any regular enemy. If you see one spawning, stand behind it, wait for it to stand up, and then use your axe. Or you can just sneak behind one and use your axe again.


> Did I Flush? - Enter the same bathroom twice
After entering 'Inner Hallway', you will come to two restrooms on your right.

Enter the first restroom, then the second. When you come out of the second, the map will have slightly changed, and you’ll be able to go a bit farther to enter the second (now third, I guess) restroom again.


> Now We're Talking - Get the pistol
When you enter the 'Loading Bay', a 3-faced enemy will spawn. There is a key right where it spawns, in the middle of the room. Pick it up, go up the stairs, enter the Loading Bay Control Room, and use the key on the box that holds the pistol.



> Spit-Take - Kill the 3-faced abomination
After getting the pistol, progress and pick up any ammo that you see. Then go back to the 'Loading Bay' and shoot the 3-faced enemy a bunch of times.


> Paradoxical Plumbing - Blow the same pipe twice, if that's even possible...
After you pick up 'Fuse B' in Storage A, you will go into a neverending repeating corridor. When it shows on the wall '2 Days Without Incident'...

...turn around and go the other direction. Smash the hissing pipe with your axe and let it explode. Don't go in the hole in the broken wall. Keep going farther down the corridor until you come to the next writing that says '2 Days Without Incident'. Now turn around and axe the pipe again.


> Marked - You have been marked. This is how he'll find you.
You will come to a room that says 'Administration'.

Enter the room, read the paper on the desk, then exit and look to your right where you came from. You will see a new enemy in the distance.

Approach it. It will fly away and leave a note- read it. Then follow it to the very beginning of the game, making sure to read every note it leaves. There are 3 notes before the elevator. Take the elevator down, and there will be 4 more notes to read.



> That Looked Like It Hurt - Hit the big bad boss in the face
When you get to the boss, let it see you. Its eye will turn red- shoot it!



> 0 Days Without Incident - Complete DWI
Can't be missed. Unlocks after finishing the game.

If you have any questions, suggestions, criticisms, found any mistakes and so on, please let me know!

Thanks to the developers for making a fun game and thank you for checking out my guide!