Thanks for all the feedback!
Yeah the walls on the ship haven't been a huge priority to fix compared to features, once we made it so you can respawn if you fall off that got deprioritized. By the steam demo we will likely have those walls a little more cleaned up. I'm actually more curious about the buoy that was under the floor - they should set their height based on the terrain, so if you happen to remember where in the map it was, I'd like to look into that further.
I'm very surprised you didn't die - the enemies used to really pound away at you but we recently nerfed the flying ones a lot so they don't overwhelm. If you're pretty good about picking up armor packs though, you can stay alive fairly easily, but the boss can be overwhelming still without a full squad. We'll probably pull down the spawn rate, maybe up the damage a little bit to make them feel more impactful but less overwhelming.
We'll look into that dust particle issue - it shouldn't play them when the ship is reversing (for that exact reason) but I have a feeling it's not syncing the engine setting over multiplayer properly. When you were going forward but shooting enemies behind you, did you feel like the dust was still in the way?
Optimization and balance is going to be a big focus for us since we are pretty much done feature wise (for the demo), so we will try to get things running smoothly. F11 works for making it fullscreen just via windows, but we are working on fleshing out those options so you can set it (and it stays that way) in the saved settings.ini.
Menus - we'll think about this...currently ESC is how you open the pause menu, meaning you wouldn't be able to go into options from those menus unless you double tapped (leave menu > open pause menu). It is intuitive though to hit ESC to leave, so we'll come up with something.
Reload button is a good idea, one we've considered before. It would mean adjusting the controls around a bit since it would be R to reload, meaning upgrades would have to be on something else (F, Q, Z, V...who knows).
UI is something we are still trying to improve, though I imagine you are talking about the ingame UI, which we recently updated, rather than main menu UI (which is our next project). We can see about adding more life to it, maybe some VFX/animations, though that might come as an update post initial steam demo release. If you have specific feedback for it though, we'd be happy to hear it.
Glad you like the steering UI and weapons design! They've definitely gotten a majority of the focus so far.
With two players, did you manage to beat the boss? Since you mentioned not being able to die in the demo that makes me curious...
Thanks for writing all this up! Looking forward to the feedback with a full crew (if you have more to share!).