From where you begin, jump to the right and land on the ground next to the leftmost bottom thwump. Run to the right until you get to the third thwump from the left, then jump and allow the floorguard to pass. Keep running past the last two thwumps, and jump up to the lowest oneway platform on the right. Jump right, then back left to get to the second oneway on the right, and jump to the middle platform in the second row. Jump to get the doorswitch, then jump to the second oneway platform on the left. Quickly, jump left, then right to get to the third oneway platform on the left, then jump up to the thwump coming down and walljump off of it to get to the fourth oneway platform on the left. From there, jump and run into the door.