@@ -0,0 +1,105 @@
+# Architecture
+
+Since 1.27 you can build rooms and houses from parametric pieces: walls with doorways and window openings, doors and
+windows that open, and four kinds of stairs. Every piece is a set of numbers you can change at any time, and doors swing
+open for everyone in the session.
+
+![A wall with a door and two windows, two side walls and a spiral stair](img/architecture/house.png)
+
+## Adding a piece
+
+Right-click the viewport ▸ **Add ▸ Architecture** (or type the name into the Add menu's search):
+
+| Group | Items |
+|---|---|
+| Walls | **Wall** · **Wall with door** · **Wall with windows** · **Wall with door and windows** |
+| Doors | **Door** · **Double door** |
+| Windows | **Window** · **Casement window** |
+| Stairs | **Stairs (straight)** · **Stairs (L)** · **Stairs (U)** · **Stairs (spiral)** |
+
+Pieces from the Add menu land on the 1 m grid.
+
+## Editing a piece
+
+Select the piece and open its **Properties**: the **Geometry** section holds every number. Rows that do not apply are
+hidden — a wall with no doors has no *Door width* row.
+
+![Properties ▸ Geometry for a wall: Length, Height, Thickness, Doors, Door width and height, Windows, Win width and height, Sill height, Shift](img/architecture/wall-geometry.png)
+
+### Wall
+
+| Row | What it sets |
+|---|---|
+| **Length** · **Height** · **Thickness** | the size of the wall |
+| **Doors** · **Door width** · **Door height** | how many doorways and their size |
+| **Windows** · **Win width** · **Win height** | how many window openings and their size |
+| **Sill height** | how far above the floor the window openings start |
+| **Shift** | slides the openings along the wall |
+
+Openings are spread evenly along the wall, centred on half metres, and a 10 cm pier always stays between them. The
+wall's origin is its **start end**, on the floor, so walls of a whole number of metres snap end to end on the grid.
+
+### Door
+
+| Row | What it sets |
+|---|---|
+| **Width** · **Height** | the opening the door fills |
+| **Frame depth** · **Frame** | how deep and how wide the frame is |
+| **Leaves** | single or double |
+| **Hinge** | left or right (a single door) |
+| **Opens** | in or out |
+| **Swing °** | how far it opens |
+| **Glass panes** | panes of glass in the leaf (0 for a solid door) |
+| **Sill** | a threshold at the bottom |
+| **Opens on** | **click**, or **proximity** — it opens when someone walks up to it |
+
+### Window
+
+| Row | What it sets |
+|---|---|
+| **Width** · **Height** | the size of the window |
+| **Sill height** | how far above the floor it sits |
+| **Frame depth** · **Frame** | how deep and how wide the frame is |
+| **Panes across** · **Panes up** | the glazing bars |
+| **Sill ledge** | a ledge under the window |
+| **Opens** | **fixed**, or **casement** (it swings open) |
+| **Hinge** | left or right (a casement) |
+
+### Stairs
+
+| Row | What it sets |
+|---|---|
+| **Shape** | straight, L, U or spiral |
+| **Width** · **Steps** | how wide the stair is and how many steps it has |
+| **Rise** · **Run** | the height and depth of each step |
+| **Turn** | left or right (L, U and spiral) |
+| **Flight gap** | the space between the two flights of a U stair |
+| **Column** | the thickness of a spiral stair's centre column |
+| **Solid** · **Tread** | a solid stair, or open treads of this thickness |
+
+## Fitting a door or window into a wall
+
+A door and a window both sit centred on their opening, at floor level. To fit one into a wall, place it on the same
+grid point as the centre of the wall's opening, with the same size as the opening (and, for a window, the same **Sill
+height**). The pieces from the Add menu already match each other.
+
+## Doors and windows that open
+
+In **Interact** and **Play**, click a door to open or close it, or walk up to a door set to open on proximity.
+Casement windows open the same way. Every peer sees the same swing, and a player who joins later sees the door already
+open. In **Edit** a door always shows shut, so it is easy to place.
+
+![A door and a casement window open in Interact, with stairs visible through the doorway](img/architecture/door-open.png)
+
+## Collisions
+
+- Walls and stairs collide with their exact shape: doorways stay open, and a walking player climbs steps up to 0.3 m
+  high.
+- A door's frame blocks around the doorway, and its leaf blocks only while it is shut.
+- A window is a solid slab.
+
+## Limits
+
+- The parts of a door or window are rebuilt from its numbers on every device, so [editing the mesh](mesh-editing.md) of
+  a door changes only its frame.
+- Very steep stairs (a **Rise** near 0.3 m) are the most a walking player can climb.
@@ -6,7 +6,7 @@ Everything about how the scene *looks on your screen* — the camera lens, rende
 
 Click **🎛️ Configure Scene** in the sidebar menu. It opens a panel on the right with these sections:
 
-- **Environment** — lighting preset, exposure, saved presets (shared).
+- **Environment** — lighting preset, exposure, [sky image](#sky-images-hdri), saved presets (shared).
 - **Music** — the shared background track and your local volume (see [Music & Sound](audio.md)).
 - **View** — render mode, camera lens, clip planes (your device only).
 - **Background** and **Fog** (shared).
@@ -69,7 +69,8 @@ everyone; previewing and the frustum lines are yours alone. The object's right-c
 screen, **✕** hides the window (the *Preview window while selected* row brings it back), and right-drag moves it.
 
 A game uses cameras through the [Set Active Camera](nodes/setcamera.md) node, the [Game Start](nodes/gamestart.md) node's
-camera, and [Set Look](nodes/setlook.md) for each camera's own [look](post-processing.md).
+camera, [Set Look](nodes/setlook.md) for each camera's own [look](post-processing.md), and since 1.27 the
+[Camera Rig](nodes/camerarig.md) node, which makes a camera follow or watch an object.
 
 ## Camera lens
 
@@ -116,12 +117,78 @@ The **Environment** section sets the scene's lighting and sky. Pick a preset chi
 | **Night** | Dim and cool. |
 | **Classic** | The pre-lighting look with the rig **off** — bring your own lights. |
 
+Since 1.27 five more chips — **Clear sky**, **Meadow**, **Sunrise**, **Starlight** and **Photo studio** — use a real sky
+photo; see [Sky images](#sky-images-hdri).
+
 An **Exposure** slider tunes overall brightness. The lit presets add a sun that casts shadows, with a shadow-catcher disc under the scene so shadows land even on the infinite grid.
 
 Environment is a **shared, latest-wins** setting — the most recent change wins for everyone. You can also **save**, **export** and **import** custom presets (stored locally), and adopt presets other peers have shared.
 
 Below Environment, **Background** sets the clear color and **Fog** adds distance fog (color + near/far), both shared. A fog you set by hand keeps exactly the near and far you typed; a preset's fog still grows with a big scene.
 
+## Sky images (HDRI)
+
+Since 1.27 a sky image — an HDRI, a 360° photo that keeps the real brightness of the sun and the sky — can be the
+scene's sky **and** its light. Every object picks up the image's colours and brightness, shiny objects reflect it, and
+[water](water.md) mirrors the real clouds. The scene's sun is placed where the photo's sun is, so shadows agree with the
+sky.
+
+![A mirror sphere and a box lit by the Meadow sky image](img/camera/sky-meadow.png)
+
+It lives in **Configure Scene ▸ Environment ▸ Sky image (HDRI)**, under the preset chips and the Exposure slider. Click
+a card to switch to that sky; like every Environment setting, everyone in the session sees it.
+
+| Sky | What it looks like |
+|---|---|
+| **Clear sky** | open blue sky with clouds, haze on the horizon |
+| **Meadow** | a sunny meadow with trees |
+| **Sunrise** | a low warm sun and long shadows |
+| **Starlight** | dusk under the stars |
+| **Photo studio** | softbox lighting over a plain grey backdrop — light only; reflections show the studio |
+
+The five skies are also preset chips, and in VR they are in the radial menu's **Scene ▸ Environment**. All five are CC0
+images from [Poly Haven](https://polyhaven.com).
+
+![Configure Scene ▸ Environment with the Sky image section: the sky cards, Upload HDRI…, Rotation, Image light, Show as sky, Sky blur and Tone mapping](img/camera/sky-image-section.png)
+
+| Row | What it does |
+|---|---|
+| **Upload HDRI…** | use your own equirectangular `.hdr` or `.exr` file (up to 25 MB; 1k–2k is plenty). It is added to the [Explorer](explorer.md), your peers download it from you automatically, and it is saved inside `.tpscene` files and exports |
+| **Rotation** | turns the sky; the sun and its shadows turn with it |
+| **Image light** | how strongly the image lights objects (the sky itself is unchanged) |
+| **Show as sky** | off keeps the image's light and reflections but shows the colour sky instead |
+| **Sky blur** | softens the background — handy behind a product shot |
+| **Tone mapping** | **ACES Filmic** (the default), **AgX** or **Neutral**: how the bright image is fitted to the screen |
+| **None** (the first card) | back to the colour sky and the light rig |
+
+**Exposure**, above the cards, brightens or darkens the whole picture, and while a sky image shows it works on the
+desktop whatever else is on. Editing any of these turns the preset into *Custom*, like any other sky edit; **Save
+preset** keeps it.
+
+A short tour points at the cards the first time you see them (**Settings ▸ Interface ▸ Tours ▸ Reset all** shows it
+again).
+
+### Sky image quality
+
+How sharp the sky and its reflections are is a setting for **this device only** — **Settings ▸ Scene ▸ Performance ▸
+Sky image quality**:
+
+| Choice | What it does |
+|---|---|
+| **Auto** (the default) | **Low** in a headset, in VR, or once the scene is too heavy for effects; **Full** otherwise |
+| **Full (1k)** | prepares the image at 1024 px |
+| **Low (headset)** | prepares it at 512 px — a quarter of the memory |
+
+The scene and your peers are unaffected.
+
+### Limits
+
+- Only equirectangular images (twice as wide as they are tall); cube-map files are not supported. An `.exr` must be RGB
+  or RGBA.
+- Files over 25 MB are refused — your peers could not receive them.
+- Someone on an app older than 1.27 in the same session sees the preset's flat colours instead of the image.
+- A [scene look](post-processing.md) with its own [Tone mapping](post-processing.md#tone-mapping) effect keeps its own curve.
+
 ## Lights
 
 A **directional** or **spot** light shines where it points. Turn it with the rotate gizmo — or type into the rotation rows — and the beam and its shadow follow, the way a light behaves in any 3D tool. Older scenes that aimed a spot at a saved point load aimed the same way.
 
@@ -157,3 +157,9 @@ Every scene page ends with **Report this scene**: pick a reason — **Spam**, **
 
 Staff accounts have a **Staff · Insights & moderation** entry in the profile menu for the report queue and the visit
 totals; it is not shown to anyone else. Assets an author had no right to license are exactly what *Stolen work* is for: the license picker cannot express "all rights reserved", so a report and a takedown are how that is handled.
+
+## What's new on theprototype.app
+
+Since 1.27 the **What's New** window (logo menu) on theprototype.app starts with a **theprototype.app cloud** section:
+what changed in the hosted service — publishing, community, rooms, hosted AI — above the app's own release notes. A
+self-hosted or local build shows no such section.
@@ -301,6 +301,26 @@ graph, and the behaviour view no longer flickers the cursor.
 Fields that hold a distance or an angle also accept a typed **unit** (`12cm`, `4in`,
 `90deg`) — see [Units](units.md).
 
+#### Number fields and undo
+
+Since 1.27 every number field you can drag — the Inspector's **Position** / **Rotation** / **Scale** and its other
+values, shader-node vectors, and the [Animation window](animation.md)'s length, speed, fps, step and key fields — works
+the same way with undo:
+
+- **One drag is one undo step.** However far you scrub, one <kbd>Ctrl</kbd>+<kbd>Z</kbd> puts the value back where the
+  drag started. (Before, a shader vector took two, and the Animation window's length, fps and step took one per pixel
+  moved.)
+- **One typed edit is one undo step.** Click a field, type a value (it applies as you type) and press <kbd>Enter</kbd>:
+  that is one step, even if you paused between keys.
+- **<kbd>Esc</kbd> cancels typing.** It puts back the value the field had before you started, as it already did for
+  arrow-key steps, and leaves nothing on the undo stack.
+- **Undo shows at once.** After <kbd>Ctrl</kbd>+<kbd>Z</kbd> the Position / Rotation / Scale rows show the restored
+  numbers straight away — before, they kept the old number until you clicked something, and dragging from it made the
+  object jump.
+- The Animation window's playback **Speed** is undoable now too.
+- **Selecting a shader node is not an edit.** Clicking a node in the [Shader editor](shader-graph.md) selects it on your
+  screen only: it adds no undo step and is not sent to the other people in the session.
+
 ### Text selection
 
 Dragging across a menu, a toolbar or a panel does not paint a text selection, and a drag that starts in the 3D view or
@@ -469,7 +489,7 @@ places keys belong to.
 **Empty viewport** — a quick right-click opens the scene menu:
 
 - **Search objects…** — find an object in the scene by name (off by default: **Settings ▸ Interface ▸ Lists & menus ▸ Object search in menu**).
-- **Add** — the full primitive catalog (meshes, building blocks, cameras, lights, [water](water.md), [effects](particles.md), a [fluid tank](simulation.md#fluid-tank)) plus empty groups; objects spawn at the clicked point.
+- **Add** — the full primitive catalog (meshes, building blocks, [architecture](architecture.md) — walls, doors, windows and stairs — cameras, lights, [water](water.md), [effects](particles.md), a [fluid tank](simulation.md#fluid-tank)) plus empty groups; objects spawn at the clicked point.
 - **Undo / Redo**, **Ping here**.
 - **Selected ▸** — the selected object's own menu (shown only while something is selected).
 - **Tools** — Node editor, Draw mode (drag 3D strokes on surfaces, or click out an editable [spline](splines.md)), Measure distance, Simulate physics (and *Reset simulation* while one runs), [Recording…](recording.md) (a turntable or flythrough video).