Merge pull request #96 from metamath/explain_temp_mode

Explain TEMP mode in tutorial

docs/11/index.md

@@ -769,27 +769,73 @@ the proof of the syntax (type) claims as well as the essential steps.
 
 #### Exporting and importing your current state
 
-You can only generate a proof once you *have* a proof.
+You can only generate a final proof once you *have* a proof.
 
 Metamath-lamp can export the current state of your efforts,
 whatever they are, and anyone can reload them later.
-This lets you share details of a proof, even one that isn't complete.
+This lets you share your current state, even if that isn't complete.
 
 > Click on the
 > icon <img width="16" height="16" src="menu.svg" alt="menu"> (menu)
 > on the top right of the display.
 
-This menu includes several ways to export and import your
-current state:
+You can save your state for reloading later in a JSON format:
 
-* "Export to URL": Provides a URL. You or anyone else
-  can use this URL to re-open the proof assistant at
-  this current state.
 * "Export to JSON": Provides the current proof assistant
   state as text; you can save this where you wish.
 * "Import from JSON": Allows you to load a state previously
   exported with "Export to JSON".
 
+If you store this information in a file they conventionally
+have a `.lamp.json` suffix.
+
+> You can click again on the
+> icon <img width="16" height="16" src="menu.svg" alt="menu"> (menu)
+> to dismiss the menu.
+
+#### Exporting to URL and temporary mode (TEMP mode)
+
+You can also export the current state into a URL:
+
+> Click on the
+> icon <img width="16" height="16" src="menu.svg" alt="menu"> (menu)
+> on the top right of the display.
+
+You can then share this URL, to easily share with others your current state.
+Anyone who opens this URL can see this state.
+
+**NOTE**: When you open a URL URL exported this way, Metamath-lamp
+is opened in *temporary mode (aka TEMP mode)*.
+Temporary mode is intended to let you view others' work
+*without* erasing your own.
+*Changes in temporary mode will not be stored* in
+the editor's content to the local storage.
+That means closing a browser or any internal error
+will erase the editor's content. That's why it is "temporary".
+
+To reduce the risk of accidentally doing something important
+while in temporary mode, the web page header starts with "TEMP"
+in any tab in temporary mode.
+Also, the first attempt to edit will remind you that you're in temporary mode
+and that changes will be discarded later. Here is the message
+you'll see the first time you try to edit in temporary mode:
+
+> Editing in TEMP mode
+>
+> You are about to edit in TEMP mode. All changes you do in TEMP
+> mode will be erased upon closing current browser tab. If you want
+> to continue editing in NORMAL mode, please do the following actions:
+> \1) use "Export to JSON" to copy current editor state to the clipboard;
+> \2) open a new tab (or switch to an already opened tab) with
+> metamath-lamp in NORMAL mode; 3) use "Import from JSON" to load the
+> copied editor state from the clipboard.
+
+There's currently no mechanism to switch from temporary (TEMP) mode
+to regular mode.
+As noted in the warning, if you want to save results from TEMP mode, use
+"Export to JSON" to acquire the current state in JSON format.
+You can then use "Import from JSON" to load the results into a normal tab.
+
 #### Looking at proof steps
 
 In Metamath, *every* step of a valid completed proof must be an