(~30 minutes of play time) Explore the long-abandoned R&D facility, collecting as many guns as you can and destroying everything in the way. We have big explorable rail guns, mysterious tunnels, and mechs.. just hanging out!
ID: m-VjHehMmaER
You'll start off unarmed for a hot minute. Find a weapon ASAP. This level is inspired by Metroidvanias so don't freak out if you get lost, just utilize the minimap to figure out where you've been and where you need to go. The structure of the level isn't ultimately too obtuse, it's key hunting at the end of the day. Once you get the three keys, head back to the earlier zone and search for the exit.
There are a few irradiated rooms that you can run through and take minimal damage, but there's a Hazmat upgrade tucked away in The Vault. You should know when you see The Vault, it's got a computer next to it that displays the name. All of the computers have some kind of flavor text if you interact with them. If a computer doesn't have an interact-specific texture then it's not necessary to progress or find secrets so don't go around touching every computer if you don't want to. Speaking of secrets, there's a LOT. I honestly lost track of how many there are. I may have overdone it. Some of them are bordering on being easter eggs.
You may or may not shoot the ceiling down with this gun. I will not elaborate on that.
There are quite a few custom-built gizmos in this level. You'll probably run into the mines a few times but if they annoy you there's a room with a display that explains their gimmick. The goal is to spice things up with traps, not to aggravate. That said, I'm proud of my mines and I've sprinkled them everywhere like pepper.
The mech room is surprisingly chill and has the only window in the facility. Feel free to look outside!