Describe changing the collision layer during a run and Layer of (#211)

- Colliders: new section "Changing the layer while the game runs". The
  Properties node of type Collider writes layer and collidesWith, and
  Layer of names the layer of an object.
- Colliders: the line saying a ray is not filtered by layers was
  outdated, Raycast has its own Layers filter.
- Behaviors: Layer of in the list of nodes.
- Development: 1619 editor checks.

Behaviors.md

@@ -228,7 +228,7 @@ playing use the same two words.
   normalized direction, so diagonals are not faster), `Compare` (two numbers count as equal up to
   float noise, a relative 1e-9, so `time - late == 6` holds without a `Round`; `Equals` does the
   same for two numbers, and for a number against a typed text that is a number, like `130`), `And/Or/Not`, `Key is down`,
-  `Mouse position`, `Mouse button`, `Is hovered`, `Is touching`, `Animation playing` (whether an animation runs on an object, its progress and time left) and `Animation length` (see [Animations](Animations)), `Get velocity`, `Current state` (name and id), `Is in state` (one boolean per state) ·
+  `Mouse position`, `Mouse button`, `Is hovered`, `Is touching`, `Layer of` (the collision layer of an object by name and number, see [Colliders](Colliders)), `Animation playing` (whether an animation runs on an object, its progress and time left) and `Animation length` (see [Animations](Animations)), `Get velocity`, `Current state` (name and id), `Is in state` (one boolean per state) ·
   actions `Move` (dx, dy, scale, dt — connect an event's dt for per-second movement; in the object's own axes, which a turned parent turns too; with *Collide with solids* it slides along what it hits, less friction, and outputs `blocked x/y`, `hit` and the contact `normal x/y`, see [Colliders](Colliders)), `Set position`, `Spawn`
   (asset input + x/y/z, optional parent → outputs the new object; the asset is picked on the node or arrives over an edge, from an `Asset` node, a variable or a list item. A pick saved while it was still a setting reads as that input's value, so older projects spawn as before; the same holds for the asset of `Is asset`), `Destroy` (removes the object with everything below it; with **keep children** on, only the object goes: its children move up to its parent (top level when it had none) and keep their place, rotation and size in the world, and the output `children` is the list of them, nearest level only. Its behaviors and its rigidbody go with it either way. In the editor run, children that are content of a placed container move up for the run only: their place belongs to the template, so the scene does not learn it), `Emit` (starts a particle source over, see *Particles*),
   `Play sound` / `Stop sound` (see [Sounds](Sounds): the asset says how loud and whether it loops, the node's

Colliders.md

@@ -158,10 +158,31 @@ does not have to be changed as well, but the shots have to name what they *shoul
   being blocked, use **Trigger (no blocking)**.
 - It filters everything alike — the engine in Play, `Move` with *Collide with solids*, and the
   collision events of the editor run.
-- A ray is not filtered by layers yet, that is #158.
+- A ray has a filter of its own, **Layers** on the Raycast node (see below).
 - Only the *last* layer can be removed in the dialog: a collider names its layer by number, so
   taking one out of the middle would move every collider below it onto another layer.
 
+### Changing the layer while the game runs
+
+A behavior changes both settings with a **Properties** node of type *Collider* (#211): add
+`layer` or `collidesWith` under `+ Property`, switch the port to *Set*, and the node shows the same
+picker as the inspector — the project's layers by name, or a tick per layer. For a figure that is
+invulnerable for a moment, a ghost that walks through walls, a carried crate that stops blocking.
+
+- The node takes the **collider itself**, not the object it sits on: `Child by name` of the owner,
+  or the `collider` output of a collision event or of Raycast.
+- It holds from the next `Move`, the next ray and the next physics step on, in the editor run and
+  in Play alike. A dynamic body resting on ground it no longer meets starts to fall.
+- A pair that still meets after the change reports no new *enter* or *exit*.
+- Read the same way, `layer` is the number of the layer (0 for the first), not its name.
+- **Layer of** gives the name: it takes an object and answers `name` (as the project calls the
+  layer) and `number`. An object stands for its first collider child, switched on or not; a collider
+  or tilemap for itself. Without a collider the name is empty and the number -1. It answers at the
+  moment it is asked, so right after a *Set* in the same flow it already names the new layer. Feed
+  `name` into `Equals` to branch on the layer.
+- Like every change a graph makes, it lasts for the run in Play; the editor run writes it into the
+  scene.
+
 ## Raycast
 
 The **Raycast** node (#153) casts a ray from `from x/y` along `dir x/y` (any length, it is made a

Development.md

@@ -18,7 +18,7 @@ php tests/php/accounts.test.php                               # the API's accoun
                                                               #   has and the web server's container has not (SKIP there)
 php tests/php/snapshots.test.php                              # the snapshot store (#231), the same way
 php tests/php/releases.test.php                               # the release store (#266), the same way
-node tools/seed-e2e.mjs && node tools/e2e.mjs                 # 1617 editor checks, screenshots in /tmp/gm-e2e-*.png
+node tools/seed-e2e.mjs && node tools/e2e.mjs                 # 1619 editor checks, screenshots in /tmp/gm-e2e-*.png
 GM_STEPS=20 node tools/e2e.mjs                                # or 1-12, or 6,20 — a subset while working on one step
 ./e2e.sh start [GM_STEPS]                                     # the same run detached, see below
 ./e2e.sh status                                               # live progress, or the last run's result