diff --git a/README.md b/README.md
index 10f5013..870c723 100644
--- a/README.md
+++ b/README.md
@@ -32,6 +32,17 @@ every participant: people and agents, with a window or without. BeamletOpticsGUI
 top of it. An agent needs no GUI: it works with BeamletOptics and BeamletOpticsProjects only. Each
 package ships its own agent skill (`install_agent_skill()`).
 
+## Installation
+
+BeamletOpticsProjects is not in the General registry yet. Install it, and BeamletOptics in the
+version it is developed against, from their repositories:
+
+```julia
+using Pkg
+Pkg.add([PackageSpec(url = "https://github.com/StackEnjoyer/BeamletOptics.jl", rev = "master"),
+    PackageSpec(url = "https://github.com/StackEnjoyer/BeamletOpticsProjects.jl", rev = "main")])
+```
+
 ## A project
 
 ```text
diff --git a/docs/src/index.md b/docs/src/index.md
index 248ab2e..1eb64ba 100644
--- a/docs/src/index.md
+++ b/docs/src/index.md
@@ -25,6 +25,17 @@ every participant: people and agents, with a window or without. BeamletOpticsGUI
 top of it. An agent needs no GUI: it works with BeamletOptics and BeamletOpticsProjects only. Each
 package ships its own agent skill (`install_agent_skill()`).
 
+## Installation
+
+BeamletOpticsProjects is not in the General registry yet. Install it, and BeamletOptics in the
+version it is developed against, from their repositories:
+
+```julia
+using Pkg
+Pkg.add([PackageSpec(url = "https://github.com/StackEnjoyer/BeamletOptics.jl", rev = "master"),
+    PackageSpec(url = "https://github.com/StackEnjoyer/BeamletOpticsProjects.jl", rev = "main")])
+```
+
 ## A project
 
 ```text
diff --git a/skills/beamletopticsprojects/FORMAT.md b/skills/beamletopticsprojects/FORMAT.md
index 35c6743..19d60f4 100644
--- a/skills/beamletopticsprojects/FORMAT.md
+++ b/skills/beamletopticsprojects/FORMAT.md
@@ -11,17 +11,36 @@ One line per entry; components first, then sources, then groups, then systems:
 
 - The name after `@component`/`@source`/`@group`/`@system` is the readable **id** (`L1`, `M2`, `D3`,
   `BS1`, `B1`, `G1`, `S1`: a prefix of the family and a number, see `id_prefix`). It is unique and stays; never
-  rename an id. Give a new line the next free number of its prefix (`next_id(p, "L")`).
+  rename an id. Give a new line the next free number of its prefix (`next_id(p, "L")`). The prefix
+  comes from the type that the code builds, and the number counts over the whole project, so
+  `add!` may give `M3` where you expected `M1`: use the id that it returns.
+
+  | Built object | Prefix |
+  |---|---|
+  | `Lens`, `DoubletLens`, `TripletLens` | `L` |
+  | prisms | `P` |
+  | mirrors and other reflective optics | `M` |
+  | detectors | `D` |
+  | beamsplitters | `BS` |
+  | sources (beams and beam groups) | `B` |
+  | groups | `G` |
+  | systems | `S` |
+  | anything else | `X` |
+
+  A package with own component types may add prefixes (methods of `id_prefix`).
 - `label = "…"` is the name that people see and change in the GUI; optional. When a person names an
-  object ("the collimator"), find its id by the label (`look(p)` shows the labels).
+  object ("the collimator"), find its id by the label (`look(p)` shows the labels). Name it by what
+  the object does, not by an id: a label "BS1 split" contradicts the window when the id became
+  `BS2`.
 - `uid = "…"` (always last) is the machine id by which the GUI recognizes the line. Never change or
   copy it; a new line has no `uid`, it gets one when the project is saved.
 - The right-hand side is any expression that builds a BeamletOptics component, group or source, also
   a call of a function of `src/<Name>.jl` (its exported names). SI units: m, wavelengths in m.
   For an own type with a method of `constructor_code`, the window writes this expression anew
   from that method when a person changes the shape on its card (see "Own code" in `SKILL.md`).
-- `pos` is the absolute position (m), `rot` the rotation since construction in degrees: first about
-  the global x-axis, then y, then z. Both are optional.
+- `pos` is the absolute position (m), `rot` the rotation since construction in **degrees** (unlike
+  BeamletOptics, whose rotations take radians): first about the global x-axis, then y, then z. Both
+  are optional.
 - `catalog = (...)` belongs to the GUI (its page "Edit"); delete it when you change the constructor.
 - `@system`: members are components; a component may be in several systems, a source in at most one.
   `static = true` makes a `StaticSystem`. Each system is traced on its own (`trace(p, :S1)`); a detector that is in several systems is the exception in the window, which adds up their hits.
diff --git a/skills/beamletopticsprojects/SKILL.md b/skills/beamletopticsprojects/SKILL.md
index 0bd2337..d963b20 100644
--- a/skills/beamletopticsprojects/SKILL.md
+++ b/skills/beamletopticsprojects/SKILL.md
@@ -20,10 +20,13 @@ When this Skill is active:
   `Pkg.activate(".")`).
   - **Check before you change the project:** `check_versions(".")` compares the versions that the
     project file records with those of the environment (`look(p)` shows them too). Tell the person
-    about `:older` (`Pkg.update("X")`) and `:missing` (`Pkg.add("X")`).
-  - **No environment yet:** if `@bmo-agent` does not exist, ask the person whether to create it
-    (`julia --project=@bmo-agent -e 'using Pkg; Pkg.add(["BeamletOptics", "BeamletOpticsProjects"])'`,
-    plus the packages under `[packages]`) or which environment to use instead. Never guess a path.
+    about `:older` (`Pkg.update("X")`) and `:missing` (`Pkg.add("X")`, for BeamletOpticsProjects
+    the line below).
+  - **No environment yet:** if `@bmo-agent` does not exist, ask the person whether to create it or
+    which environment to use instead. Never guess a path. BeamletOpticsProjects is not in the
+    General registry yet, so both packages come from their repositories (plus the packages under
+    `[packages]`):
+    `julia --project=@bmo-agent -e 'using Pkg; Pkg.add([PackageSpec(url = "https://github.com/StackEnjoyer/BeamletOptics.jl", rev = "master"), PackageSpec(url = "https://github.com/StackEnjoyer/BeamletOpticsProjects.jl", rev = "main")])'`
   - **Change an environment only after the person agreed:** adding or updating packages compiles
     them again and changes everything else that uses the environment; say so when you ask.
 - **The optics comes from the `beamletoptics` skill** (units, +y optical axis, constructors,
@@ -91,7 +94,8 @@ Bench/
    - `id = add!(".", "RoundPlanoMirror(0.0254, 0.006)"; pos = (0.1, 0.2, 0), rot = (0, 0, 45),
      label = "fold", systems = [:S1], by = "claude")`: picks the next free id of its prefix in the
      same write (no other participant can take it meanwhile) and returns it; a source goes into
-     the `sources` of one system.
+     the `sources` of one system. `pos` is in m, `rot` in degrees (not radians as in
+     BeamletOptics); the prefixes of the ids are listed in `FORMAT.md`.
    - `set!(".", :L9; pos, rot, code, label, by)` changes only the given fields of a line (a group:
      its label; move groups with `move!`).
    - `move!(".", [:G1, :FIOS1]; offset = (0.3, 0, 0), rot = (0, 0, 10), pivot = :center, by)` moves
@@ -212,7 +216,9 @@ The windows show every participant at the object it works on, people and agents
 - `announce(".", name = "claude", doing = "aligning L2", selected_id = "L2")` writes your presence
   file `.bmo/presence-<name>@agent.toml` (see the docstring of `announce` for its fields). `name` is
   your id and must be unique among the participants (`"claude-w1"` for a worker of a team): the same
-  `name` is the same file. Call it again when you go to another object. After you wrote the files,
+  `name` is the same file. `selected_id` places your `doing` at that object in the windows;
+  without it, the windows show it in a corner of the view. Call it again when you go to another
+  object. After you wrote the files,
   call it with `wrote = true`: only then it publishes the stamp of the files (`written`), by which
   the windows name you as the writer of a change, also if they merged the change before your call;
   without `wrote = true` the `written` of the file before is kept.
diff --git a/src/New.jl b/src/New.jl
index 5ad93a2..2b3e943 100644
--- a/src/New.jl
+++ b/src/New.jl
@@ -187,7 +187,10 @@ _agents_template(name, marker) = """
     ```julia
     # julia --project=@bmo-agent, once, after the person agreed
     using Pkg
-    Pkg.add(["BeamletOptics", "BeamletOpticsProjects"])   # and the packages under [packages]
+    # BeamletOpticsProjects is not in the General registry yet: both from their repositories
+    Pkg.add([PackageSpec(url = "https://github.com/StackEnjoyer/BeamletOptics.jl", rev = "master"),
+        PackageSpec(url = "https://github.com/StackEnjoyer/BeamletOpticsProjects.jl", rev = "main")])
+    # and the packages under [packages]
     ```
 
     ## Check