The first section has a lenient first elevator, an extremely tight second elevator, and a somewhat tight third elevator. 2 rooms on the other side of the elevators can be cleared on your way up. The way down clears out the rest. Spacing shots is important. If you hit certain doors the black suit guys will react, open them, and start patrolling. Letting them out has a small chance to save time, but usually they'll get stuck on the elevator side and cause a time loss/reset finding them.
The bomb on the elevator will cause both doors to open. Destroying it makes it easier to deal with 1 side of the basement at a time and allow for more 'box steps'.
You can do a 'box step' on wide objects that provide cover. By tapping down at the right time, they can teleport you ahead a few pixels. I did this a few times on the long basement hall (and forgot to use it at 3 obvious moments).
To anyone interested in submitting a run, at least one mod (Wavuvi) is checking for new runs multiple times a week. Remember to jump cancel your shotgun slowdown and turn off ALL skills (including team) for fresh runs!
