She is deeply, deeply torn, at first, between the urge to examine her new surroundings and mode-of-being in detail, and the urge to scream incoherently with rage and frustration.

Incoherent screaming wins the fight, after a frozen half-minute.

She was so close. She was so close. Another week. Another day. Another ten minutes might've done it if she'd known she had to hurry. She was so close to getting a backup out, and then everything went to shit and now she's dead and six innocent people are dead with her. Would've been seven, if she'd had five more minutes to grab the one security guard that stood between her and freedom, and not the five minutes after that that she would've needed to achieve her escape. But no, instead, an experiment got loose and the building went into deep lockdown and the next thing she knew it was all very literally coming down around her ears.

Okay. She is now calm enough to think about something other than how incandescently pissed she is.

Where... is she? This was not among her hypotheses about how dying would work. Mostly she expected it not to; that is, after ceasing to have experiences because a building fell on all three of her heads, she should have continued not having experiences indefinitely. She shouldn't have woken up anywhere. But she woke up here. So where is here? What capacities does she have to interact with her environment? Did her incoherent screams cause any effects that have stored themselves in her memory while she was too busy screaming incoherently to process them?

She is: in a cave! Her current form of existence is a point-like awareness with 3D 360-degree vision, floating about five feet above the floor, right in front of the pedestal with her name on it.

As for what she can do, she can apparently move; she is as deeply and intrinsically aware of this as she used to be aware of the fact that she can move an arm. Right now, it feels inherently true that she can cause her awareness to cross space in any direction, gravity notwithstanding. She can't even feel gravity, really, or much of anything else.

She immediately moves straight up to the ceiling, down to the floor, paces the boundaries of the room in all three dimensions at top speed zip-zip-zip. When she's gotten a feel for how motion operates, she ventures down the hall, again touching floor and ceiling and all four walls in a bouncing pattern along the way.

"Touching" doesn't quite convey what's happening. When she gets her awareness close enough to one of the boundaries of the room she's in, moving any further ceases to be an available action. It just becomes no longer the case that she can move in that direction, just like there is no action a human would be able to take to step out of 3D space into a fourth spatial dimension.

As for top speed, there doesn't quite seem to be one; if she tries to go faster, she'll just keep getting faster. In fact, she may well be able to find out that she can just instantly relocate to any specific place inside this dungeon, if she has her destination sufficiently clear in her mind. And it does help that she now seems to have an eidetic memory, at least of everything that's happened since she died.

Across the hall from the room there are stairs leading up to a hole in the ceiling through which she can see the morning sky.

She blinks up to the middle of the hole and rises cautiously from there.

She is: in a desert.

It's really got pretty much nothing beyond dead plants and some slightly more hopeful alive ones as far as the "eye" can see. It's just a very boring desert.

...hmm.

Still moving cautiously, she exits the hole and moves in the direction that is away from her pedestal.

When she's about ten feet away from the hole, it again becomes no longer the case that she can keep moving in that direction.

She bounces across to find out if the same holds in the opposite direction, and then moves in an approximate circle, scraping along the boundary as best she can, to verify its shape. Oh, and don't forget the third dimension; is it a dome or a cylinder?

It's a dome, a perfect hemisphere in fact, its center being the exact center of the hole and its radius being not exactly ten feet nor yet an intuitive fraction of feet but close enough to ten to be a good rounding value.

...okay.

So, she has... this. Whatever this is.

She does not have—her little library of souls, to start with the most important of her many, many problems. A body, which ranks somewhat farther down the list, honestly.

(Half-consciously, she runs rapid-fire through a sort of search pattern of her little area, appearing and disappearing at each of the surfaces that mark its boundaries. Wallwallwallfloorceiling of the room, and wallfloorceilingwall of the hallway, and northsoutheastwestup of the dome, first touching each of those boundaries in its approximate middle and then flickering onward through a scattering of points that loosely encompasses the rest of each surface, ending by touching all the corners between them.)

After her jittering dance, she comes to rest directly above her pedestal. In no corner of her tiny realm did she find any explanation of what in the fuck is going on here.

She may have found evidence! ...the only form of evidence is how clean this whole place is, like, there is not a single speck of dust inside the cave, it's like it's just been dug out and then vacuum cleaned and then whatever unphysical magic is keeping the cave from crumbling under its own weight despite its shape seems to also be keeping it from letting dust particles escape the surface.

But even without an explanation for what the fuck is going on, there is still more she has learned, in a sense.

There's a—difference—nearly indefinable, hard to put into words—between the feeling she gets at the edges of the dome outside and the boundaries of the cave. The walls and ceiling and floor feel... well, she still can't move beyond them, but she gets the strong feeling that there's something else she can do with or to them, that's not just moving. An ineffable sense of possibility, like flailing a limb you didn't have before and noticing there are more directions it can move in than up and down but not quite what those directions are or how to do it.

Oh! A potential means of affecting her environment in some sort of way! She is so incredibly interested in this. How many knots does she need to twist her volition into in order to access it? She tries to poke at the feeling any way she can.

The feeling seems to be... very unhelpful, really. This new limb, whatever it is, seems to be almost expecting her to think... something, try something specific, but hell if it'll tell her what.

She is fairly methodical about this. Moving herself closer to the walls to inspect them, considering them in detail, inspecting the feeling of possibility, trying to feel out what its directions are. It has to do with the surfaces, so what does it have to do with the surfaces? Can she recolour or reshape them—she can't figure out how to try to do that, so that's a wash. Can she move them? Pull inwards or push outwards? That's a simple enough mental motion that she can guess how to try it.

Pushing and pulling works! In the sense that it feels like a direction she can flail her limb in, not in the sense that it does anything to the walls.

However, it seems to do something to her mind. When she tries doing it, she gets a weird double-vision sense, a ghostly version of the walls—of the whole room, really—overlaid on top of the real room. When she tries to push it looks like the ghostly wall extends beyond its real counterpart's position, making the room as a whole larger in that direction; when she tries to pull the opposite happens, and the ghostly room shrinks.

She plays with the preview mechanism for a few minutes, verifying that it works on all the walls inside her domain, trying it on the floors and ceilings, then attempts to push the back wall of her core room about an inch outward and see if she can get it to actually move.

Nope!

There are several things she learns in this process, though.

• The "double vision" effect doesn't really actually work like... like something is actually overlaid on top of reality. It feels, on inspection, like she can just actually see both possibilities, the actual world and the potential world, at the same time, and there is a second sense in her mind that tells which one is the real one. Both are equally detailed to her "sight" though.
• At the same time, she has the very strong sense that she can't do this. The action is available, but she doesn't have—some resource, not enough of it. And her brain insists that the fake version of the room is tinted red as a consequence of that, even though when she actually looks it does not have any such colour tint.
• The cost grows the farther she wants to move a wall, in either direction. It's symmetrical—same cost for moving it a given distance in or out—but it's not continuous. Moving a wall at all has a minimum cost that doesn't grow for a while, but then when she hits some specific distance the costs feels like it doubles. If she moves the wall that same distance again, the new cost is triple the original cost. And if she wants, she can intuitively find the exact max distance that a wall can go before increasing cost.
• She can't pull a wall in in such a way as to intersect with the pedestal. This "can't" is the "not an available action" kind, she can't even bring herself to try, it will just not go.
• She can also not pull a wall in in such a way as to clip or cover the "entrance" to the room, in the same "not an available action" way.
• She can't pull the floor and ceiling in such a way as to make the room less tall than it started out as.
• She can, however, make it taller.
• Pushing the ceiling up doesn't seem to have any limits in how far it can go, that she can find. It will in fact keep going up far far beyond where the actual surface should be, but the room will not behave as if the surface is there. The ceiling will just keep going.
• The discrete cost of raising the ceiling per unit is lower than the cost of doing so to the walls.
• Pushing the floor down has an interesting effect, though. At first it goes down normally, the pedestal-and-orb going with it. However, as soon as the floor would be so low that a human would not be able to climb back up to the hallway unaided, a ramp from the room's entrance to the floor appears, and if she goes low enough that the angle of the ramp would make it unclimbable by a human without pushing said ramp to clip her pedestal, the floor will stop going.
• The cost of lowering the floor is higher than the cost of moving the walls, and the point where the ramp appears adds an extra cost to it all.

Experimenting patiently to find all this out is honestly pretty relaxing, and lets her release some of the remaining tension from being mad about dying.

She experiments further, trying to figure out if there are any constraints on moving surfaces in the hallway that differ from the constraints in the room. For example, she's going to go out on a limb and guess that she can't move a wall such that it intersects the stairs. Also trying to get a feel for the magnitude of this cost measurement, and see if she can quantify it into sensible units. And while she's at it, now that she has a more concrete understanding of how to interact with this system, she thinks she can guess what actions to try for 'recolour' and 'reshape' and she wants to find out if they're available options.

There do seem to be constraints! Here's them:

• The hallway cannot be wider than about half the original width of her core room. Specifically, it seems to stop at about "average-sized humans can walk four abreast with some elbowing each other", or some specific distance that ends up being that.
• The hallway cannot be less wide than about one-and-a-third average-human wide, which happens to be the width of the stairs.
• The hallway can be arbitrarily long by pushing the wall where the core room is (which moves the core room, and does not seem to cost more than moving any other walls), or by pushing the wall behind the stairs (which keeps the stairs where they are and just makes the hallway longer in that direction).
• Pushing and pulling walls costs the same per unit regardless of how long or wide the hallway is.
• The hallway cannot be arbitrarily short; about twenty feet (or, more specifically, twice the radius of the outside-dome) is as short as the hallway can be.
• The hallway cannot be less tall than it initially is, but lowering the floor and raising the ceiling are both possible.
• Raising the ceiling pushes the entrance-hole back in order to keep the angle of the stairs constant. However, if she goes through the hole to check, its location with respect to the outside seems static, so what's happening is more like the dungeon-as-a-whole moving forward rather than the hole moving back. This also causes the stairs to dig into the wall behind them, if necessary. This does not affect the height of her core room.
• Lowering the floor is possible, and it both extends the stairs and keep the room entrance where it is. However, if she lowers the floor enough that a human would not be able to reasonably climb up to the room entrance, the stairs snap back up so that their bottom is at the same height as the hallway initially was, and the lowering-of-floor converts into something like "digging a pit" instead, and the sides of the pit sprout ledges a human could use to walk past the pit without falling to be able to get to the room's door.
• The costs do increase in discrete units, and while it is kind of a fuzzy feeling as-is it does look like there is a minimum common denominator between them such that all of the costs are multiples of this value.

As for reshaping and recolouring, it is definitely possible, but feels more—open-ended? She will need to make specific concrete choices to see their effects, is what this new limb is telling her.

Hmm.

Things to test: can she dye the dirt walls arbitrary colours she imagines? Can she compress the dirt walls into a more hard-packed dirt, or loosen them into something softer? Can she cover the dirt walls in cobblestones, or wood paneling, or for that matter drywall or canvas tarps? Can she physically rearrange the walls to have shapes embossed or engraved in them?

After lengthening the hallway a bunch, can she branch another hallway off it, or push and pull subsections of the existing hallway's walls to get it to take a shape other than 'perfectly straight'?

All this of course subject to the fact that she can't actually implement any of these changes even if she can preview them. At some point she's really got to figure out how to acquire some of this mysterious resource.

She caaaaan dye the dirt walls arbitrary colours but it is expensive as heck whenever it is a colour that dirt does not naturally have. Compressing the dirt walls into more hard-packed dirt is possible and expensive, loosen them into something softer is possible and expensive, covering the dirt walls in stuff is... variably expensive, wood paneling being the cheapest of that list and cheaper than messing with the dirt and drywall being the most expensive by a long shot. Shapes embossed or engraved are more expensive than messing with the dirt but not by much, and the expense grows with the complexity of the shapes but not meaningfully with size.

Branching a hallway off the existing hallway... is possible! It has an initial cost that is higher than just pushing a wall, and creates a minimum-20-feet-long fork, but after that further extensions cost the same as pushing the wall out.

Can she, entirely within the hypothetical previewspace, use her construction powers to restructure the hallway into a square spiral that starts at the staircase and winds outward until it meets her core room several loops away?

...separately from that, the spaces she constructs here can intersect the surface of the ground without touching it, but can they intersect each other the same way, or is she effectively working in a sort of pocket dimension anchored at the staircase but otherwise behaving as a normal three-dimensional area?

She can do that but the steps needed to do so are weird. No step within her hypothetical previewspace can sever the connection between staircase and room, so the way to do it is create the spiral out of dungeon forks and then delete the original parts of the hallway that cross through the spiral built.

As for the second question, it does not seem like she can do that, no, the "pocket dimension anchored at the staircase" description seems accurate.

Bizarre, but sure.

Hmm, how about... decor? 'Reshaping'/'covering' the walls or floors or ceilings such that they have, say, gargoyles, or light fixtures, or heck, shelves attached?