Well...
I've been searching for quite sometime now.
I have the blue key since you get it about the 2nd room, I've bested any robots down there, but I don't find anymore keys...
I'm pretty sure I've explored all the places I could go except for some secrets.
I'm just running circles and can't seems to find the next step.
I've backtracked from the begginning "used" any walls I could get to, openned everydoors, cleaned the map, but nothing...

Am I missing something obvious ? (I got very quick within the corridor of death - the one you get activating 3 buttons then getting in the elevator, my guess is maybe I've missed something there, since you can't get back, but if that's the case => very bad lvl design)

Edit: I forogt the most important, the game is cool for the moment, melee build seems kind of OP against the bosses...

So red card is within that corridor.

That needs to be fixed, You can't let the player run around searching something he can't access because he missed one detail within a fast paced shooter - maybe make the first elevator go downward once you use the one to get back below.

If it was for a secret that would be ok, but this is core element to get passed the lvl.