Okay well then I misunderstood what happened, and yeah if you can shoot then you're not softlocked, at least I don't see how it could happen.
So the door right beside the helmet locks when going outside?
If that is the case then that is not supposed to happen, you should be able to go back in as long as you haven't fallen down the room with the sentry enemies, because then you wouldn't be able to jump back up.
The hint here is supposed to be that the screen goes all, I don't know "smokey", and you start taking damage indicating that this is not what you're supposed to do.
And then I'm hoping that the player would "instinctively" run back, but if the door is locked, then.. you know, that doesn't work too well. ;)
I could make the helmet required before leaving the room but I think this way is more fun, because if you just run past it / miss it or whatever, then you have to think a little bit extra.
And sure, the player could think there's a softlock there or that the game is broken or whatever but to be honest, with the way I'm making the game, if this "barrier" can't be broken then there's not much hope of the player getting much further anyway.
But if the door locks as you said, then that is incorrect and will be fixed.
Oh and I just realized you might mean the left door in the room with the helmet?
If so, that door is supposed to be locked and does not prevent the player from anything, it's the left door in the room right after the helmet I'm talking about.
And for the Super Metroid way of doing things, this is exactly what I'm trying to do, except a tiny bit different depending on what item it is.
Like what we're talking about here for example:
You can leave the room without the helmet, but you can't get very far and you can return back (if you haven't fallen down the sentinel room, this is something I probably will change so you can go back), assuming the door isn't locked that is, which it shouldn't be.
Sorry for the reply getting way too long but I'm just trying to explain what is supposed to happen here.