Part 2 is about metapuzzles, and I'm sticking to that. But what the metapuzzles are is changing, because Salvage Points don't really make sense - Doors (and Filters) aren't important enough in this progression, and Scanners have been more important but there'd be no use in Salvaging them. The connections between the themes and what's being introduced is unfortunately a little looser here, but hopefully I've towed the line between theme adherence and Part 2 meta progression well enough.
Autumn Woods introduces two new objects.
Clearing Clouds, clouds that take you to a "clearing" in the forest, are sort of a mix between a Cloud and a level entrance: they take you to another elevation while retaining your coordinates like a Cloud does, but they reset your inventory and reset any changes to the level's doors, pickups, etc. (hereafter I'll refer to that collective as the "architecture" of the level) like a level entrance does. They don't take you to a separate level, though - backspacing or reaching the goal will still take you back to whatever level you were in before this level, not just to the previous elevation. Although they're not really separate levels, this still kinda acts like you're transitioning between separate levels but with your location intact.
Alcove Entrances (which, as the name implies, are entrances into forest alcoves) are level entrances that do not reset your inventory or reset the architecture, meaning the level outside and the level inside sort of act as parts of the same level. You can still backspace out of the alcove level to return to the outside level, but since the entrance didn't reset your inventory or reset architecture, neither does exiting, so changes you made to both levels are retained when you switch between the two (but if you go through a regular level entrance at some point then both are reset). This is a level entrance, not a cloud, so when you enter an alcove you go to the start of that level, position is not retained.
Frozen Palace ups the ante with more cloud and level entrance variants. Some candidates I think could work here (though I don't think all of them are included) include:
Fog Clouds, clouds that are too foggy from the snowy air to see through, are like regular clouds, except you get lost when crossing through them and thus they put you at the start of the room they take you to instead of retaining location. Each elevation room has its own start location, and the start locations aren't necessarily in the same position as the other elevations. Fog Clouds, like regular clouds, may be repeatable or collapsing.
Windy Clouds show visions of another place, but the icy wind is strong and can push you out before you get to be there for long. These are like regular clouds, except they update your backspace chain as if they're a level entrance, so when you backspace or reach the goal, you'll be sent to the elevation you were on before going through the Windy Cloud rather than going all the way back to the previous level (you could then backspace again from there to go back to the previous level, of course - it's only hubs that outright can't be backspaced out of). Since entering the Windy Cloud did not reset your inventory or the architecture, neither does backspacing out of it. These may also be either repeatable or collapsing.
Landslide Entrances are level entrances that you're "stuck" in once you enter, and they're sort of the opposite of Windy Clouds: they're standard level entrances (reset your inventory and the architecture, and do not retain location), but they do not update your backspace chain, so they can't be exited back to the level you came from, backspacing out of them will return you to the level before that.
Collapsing Alcoves are like Alcove entrances, except they're one-time use, so when you exit the alcove the entrance is gone. They do reappear if you then enter another entrance that does reset architecture, though.
Tunnel Entrances, level entrances that in this world are themed as tunnels through caves, are like regular level entrances, except position is retained. These can also be thought of as "Clearing Clouds that enter a separate level, meaning they update your backspace chain".
Sunshade Castle is where the truth of the objects introduced in the first two Chapters is revealed: elevation and levels are the same thing. Every room in the game is actually part of one giant elevation stack, and all of these cloud and level entrance variants are different instances of the same general object - from this point on, the term "entrance" refers to this archetype as a whole. Entrances come in many different types, with the following possible attributes:
- When it comes to reusing the entrance, there are three possibilities: Once (the entrance disappears after being used once, gone until the next time the architecture is cleared), Repeatable (the entrance does not disappear after being used), and Clear (the entrance "clears" (resets) the architecture when used, which automatically means it's repeatable since any Once entrances return when the architecture is cleared anyway. Once and Repeatable entrances do not clear the architecture, only Clear entrances do.).
- Two possibilities for what happens to your inventory (your counts of keys and other collectable items): Keep or Lose. (An interesting note: the Spirits haunting Lily are reset on architecture clear, not on inventory loss. Architecture clears are also what reset Phases.)
- Four possibilities for how backspacing works: None (the backspace chain is not updated, so backspacing out of the room will send you back further than the previous room - it'll send you back to whatever room you were in before your most recent non-None entrance), Free (updates the backspace chain, and backspacing out will not reset your inventory), Expensive (updates the backspace chain, and backspacing out will reset your inventory), and Hub (completely resets the backspace chain, so you can't backspace out of the new room at all). Reaching the goal performs the same thing as a backspace. A backspace will cause an architecture clear if and only if any Clear entrance is un-crossed in the process of the backtrack (i.e. the most recent Free or Expensive entrance was a Clear entrance, or any entrance between then and your current room was a Clear entrance).
- Two possibilities for position: Jump (it acts like a cloud, retaining your position) and Transport (it acts like a level entrance, sending you to the starting position of that room).
That's a total of 48 possibilities for entrance types. The ones that may have appeared so far are CLET (standard level entrances), CLHT (standard world/hub entrances, and this is the kind of entrance that the Warp Rod causes), RKNJ (regular clouds), OKNJ (collapsing clouds), CLNJ (clearing clouds), RKFT (alcove entrances), RKNT (fog clouds), OKNT (collapsing fog clouds), RKFJ (windy clouds), OKFJ (collapsing windy clouds), CLNT (landslide entrances), OKFT (collapsing alcoves), and CLEJ (tunnel entrances). These have all had special sprites, but from this point on there's probably a more standard sprite used for entrances in general that looks like a mix between a cloud and a level entrance, with colored quadrants to indicate what its four attributes are. The most basic ones like standard clouds and level entrances probably still use their special sprites, but from Sunshade Castle on, the ones introduced in the first two Chapters probably just use the standard entrance sprite, to help with the shift in thinking about how they work, not as special objects but as part of a greater archetype.
In addition to any of the entrances on the Frozen Palace candidate list that didn't make it in there, entrance types that might first show up in Sunshade Castle may include the following:
- CKNJ: These are like clearing clouds, but you keep your inventory when you go through them.
- OLNJ and RLNJ: These are like standard clouds, but you lose your inventory when you go through them.
- CKNT: Similar to fog clouds, but architecture is reset, so it feels more like you're going between two separate levels but keeping your keys (and not updating the backspace chain, so the two are still part of the same puzzle)
- CKET: I call these "delivery" entrances. You keep your inventory when you go in, but lose it when you backspace out, so with these you'd collect keys in the outside level, then enter the delivery entrance to use those keys within.
- CLFT: "Starter" entrances, which are the opposite of delivery entrances: you lose your inventory when you enter, but not when you exit.
- OKET and RKET: Delivery entrances that don't reset architecture, making them "drop-off" entrances: go partway through the outer level, drop off your inventory in the inner level, then pick up where you left off on the outer level with a fresh inventory.
- OLFT and RLFT: Starter entrances that don't reset architecture, making them "restock" entrances: go partway through the outer level, ditch your inventory and get a new one in the inner level, then pick up where you left off on the outer level with your restocked inventory.
Those last four bullet point examples can have their Ts replaced with Ls to make location matter. Those last two bullet point examples probably don't show up until The Dream Labyrinth but I figured I'd mention them in my list of notable ones anyway.
If elevation and levels are the same thing, then what's going on with doors and other objects that take up multiple elevations? The other thing Sunshade Castle reveals is Shadows: the same object can exist in multiple locations at once (these are called "shadows" of that object), and collecting/destroying it anywhere will remove all of its shadows. Objects that take up multiple elevations are actually objects with multiple shadows in the same position at different elevations, but now shadows don't have to be in the same position or on consecutive elevations, they can be scattered around different places and rooms. Shadows, like everything else in a level, are restored when the architecture clears. There's no "primary object" that the rest are shadows of, all shadows of an object are on equal footing.
As in canon IWL, the Dream Labyrinth is where the meta mechanics stop pulling any remaining punches. Here that process already started in Sunshade Castle, but the Dream Labyrinth certainly ups the ante, with even more entrance types being thrown around and used in more complicated ways, making navigating the entrances itself a major puzzle on each step of the way - which entrances do you use and when? Spirits that change elevation have been absent for the past three Chapters, but there's at least one of those that shows up here, with all the implications that changing elevation now has; these elevation jumps, which in The Miracle Tower were always considered RKNJ jumps, can now be of any of the 48 types (although Once and Repeatable are indistinguishable in the context of a Spirit effect, and if the jump is a Clear jump then once it occurs you lose your Spirits after the jump). This is also where Blueprint Entrances, which set your elevation to a specific value instead of incrementing or decrementing it relative to its current value, start showing up; Blueprint Entrances weren't needed before since each cloud/entrance was on just one layer of elevation, but now with Shadows around, non-Blueprint entrance shadows would take you to different elevations depending on what elevation you were on before. More importantly, Blueprint Clouds couldn't have been shown before now, because the "every room is part of the same elevation stack" means that the exact elevations are weird numbers in the hundreds or thousands (depending on how much protection from shenanigans is needed), so showing them before now would have given away that something weird was going on with elevation.