Kokkoja as of 2026-10-10: the teacher's requests, the Session window, notices, the QR code, the license

docs/introduction.md

@@ -33,7 +33,7 @@ layer of its own.  You can erase your own writing and nothing else; nobody
 else can erase yours.  Any layer can be hidden on your own screen without
 affecting anyone else's view.
 
-**A page that grows.**  A page is an A4 sheet.  When writing approaches an
+**A page that grows.**  A page is an A4 sheet, lying on its side.  When writing approaches an
 edge, the sheet grows in that direction, so you are never short of room.
 An image is placed at its natural size; one wider than the sheet is
 scaled down to fit, and the sheet grows downward to hold further images.
@@ -62,8 +62,9 @@ host runs Kokkoja.
 
 **Free software.**  Kokkoja is free and open-source.  Anyone can use it
 without paying, and nobody depends on a company's service.  It runs in
-Firefox and in browsers built on the Chromium engine, such as Brave and
-Chrome, on Linux and macOS.
+Firefox, in browsers built on the Chromium engine, such as Brave or
+Chrome, and in Safari, on Linux and macOS; a guest can also join from
+Safari on an iPad or an iPhone, writing with a pencil or a finger.
 
 ## Who uses it
 
@@ -93,8 +94,52 @@ A session has one *host*, the person who starts it, and any number of
 guests.  The host sends the guests an invitation, by email, in a chat
 message, or by any other means.  The host *drives*: only the host puts
 images on the page, starts new pages or loads pages from a notebook, and
-everyone follows.  The host can give any guest the same abilities, for a
-discussion among colleagues.
+everyone follows.  The host can make any guest a *co-host*, with the
+same powers, for a discussion among colleagues.
+
+## What runs where
+
+Three kinds of machine take part, and it helps to have the picture in
+mind before reading on.
+
+```
+   Host's computer                 Server                    Guests
+   ---------------                 ------                    ------
+   Kokkoja program            kokkoja.andykopra.com      Guest A: a browser
+     serves the client  -+        |                        opens the link
+     to the browser at   |   +----+-----+                  the server serves
+     localhost:8760      |   |  relay   | <------------->  the client to it;
+     keeps the notebook  |   | (passes  |                  notebook in the
+     as files            |   | messages,|                  browser, downloads
+          |              |   | reads    |
+     browser <-----------+   | nothing) | <------------->  Guest B: has the
+       |                     +----------+                  Kokkoja program too;
+       +---- encrypted ----------^  |                      joins from its own
+             messages               |                      start screen; note-
+                              web site:                    book as files
+                              the client's files
+```
+
+* **The host** runs the small Kokkoja program on their own computer.
+  It shows Kokkoja in the host's browser, at the address
+  `http://localhost:8760/`, and it keeps the host's notebooks as
+  directories of files.  It must be running for as long as the host is
+  in a session; the browser alone cannot reach the notebooks.
+
+* **The server** does two things for everyone.  Its *relay* passes the
+  participants' messages, which are encrypted before they leave each
+  computer, so the relay reads nothing.  Its *web site* serves the
+  Kokkoja client to guests who join by link.  The host's program is
+  told the server's address once, when it is started.
+
+* **A guest** needs only a browser: opening the invitation link fetches
+  the client from the server's web site, and the guest's notebook lives
+  in that browser, with kept pages and exports offered as downloads.  A
+  guest who wants a notebook of real files runs the Kokkoja program as
+  the host does, and joins from the program's own start screen.
+
+Every participant's computer holds the whole page.  Only changes travel,
+through the relay, to everyone else.  Nothing is stored on the server.
 
 The rest of this documentation describes Kokkoja from the guest's point of
 view first, since the host sees the same screen and has a few more