This is a guide for the optimal glitchless route in One Leaves. There are three RNG controlled factors that determine success. They are the school, the hospital, and the ending sewers.

School: At the start the door past the gate has to have a large chunk out of the wall next to it. If so, you'll run to the door, open, turn right and enter the vent. As soon as you exit the vent go left to the end of the hall, through the doors, and up the stairs on the left. Turn left on the second floor and follow the wire into your first puzzle, the looping hallway or the library.

For the looping hallway you'll need to go down the hallway, go a little bit past the first pair of lockers, turn around back down the hallway, and flip the switch. Turn around and go through the now open exit.

For the library you'll have to interact with the first bookshelf, run through to interact with the second, and turn around to interact with the first again. Turn around and run the the opened exit.

Both exit paths will lead you back to the doors you opened to get there, so from those doors you'll now run to the other end of the hall (watch for the book that flies across the hall both times) and go through the doors there, where you'll go up follow the wire that goes forward on the second floor which leads to the second puzzle, the one you didn't get before. The exit from that puzzle will lead to another exit path that takes you back to the doors you came from once again. You'll go through the doors you opened and follow the wires to the checkpoint and the elevator downstairs, which leads to part two.

Hospital: When the elevator opens look for an 'H' sign at the end of the hall. If it's there, reset, otherwise you have to do two puzzles instead of one. If it's not there, contine forward then left into a room with three switches. Flip the one closest and furthest from you, then head towards the iron lung and wait for your flashight. Pick up the flashlight and follow the wire through the gate into the only puzzle in this part, the morgue.

Here, you need to open one of four vents and crawl in. The correct one is randomized so you might need to reset. After choosing the the vent following it, you'll drop into a room with a switch and a door to the right. After interacting with it leave through the door and head left, following the wire to the checkpoint and then downstairs where you'll have to go through a small mess to reach the elevator leading to the final part.

When the elevator opens for the sewers sprint forward and into the hole in the ground. If you can go through the path to your left reset, or you won't be fast enough. You need to run forward, toward the gated hole, and into the archway on your right. You should see someone running to the right. Instead go left and left again through the first archway you can. The exit will be on your immediate left where you'll run up the stairs and, as SpicyParmesan said in his guide, go one of two routes. If you see a crow behind the first grated wall you'll go "left, right, right, left, left" otherwise you'll go "right, left, left, right, right" and you will reach the exit.

I hope this helps anyone. Be sure to practice your turns and shift jumping :)