Adding a dedicated doc for variables

docs/maps/api-state.md

@@ -14,7 +14,7 @@ WA.state.onVariableChange(key : string).subscribe((data: unknown) => {}) : Subsc
 WA.state.[any property]: unknown
 ```
 
-These methods and properties can be used to save, load and track changes in variables related to the current room.
+These methods and properties can be used to save, load and track changes in [variables related to the current room](variables.md).
 
 Variables stored in `WA.state` can be any value that is serializable in JSON.
 
@@ -63,44 +63,11 @@ that you get the expected type).
 For security reasons, the list of variables you are allowed to access and modify is **restricted** (otherwise, anyone on your map could set any data).
 Variables storage is subject to an authorization process. Read below to learn more.
 
-### Declaring allowed keys
+## Defining a variable
 
-In order to declare allowed keys related to a room, you need to add **objects** in an "object layer" of the map.
+Out of the box, you cannot edit *any* variable. Variables MUST be declared in the map.
-
-Each object will represent a variable.
-
-<div class="row">
-    <div class="col">
-        <img src="images/object_variable.png" class="figure-img img-fluid rounded" alt="" />
-    </div>
-</div>
-
-The name of the variable is the name of the object.
-The object **type** MUST be **variable**.
-
-You can set a default value for the object in the `default` property.
-
-### Persisting variables state
-
-Use the `persist` property to save the state of the variable in database. If `persist` is false, the variable will stay
-in the memory of the WorkAdventure servers but will be wiped out of the memory as soon as the room is empty (or if the
-server restarts).
-
-{.alert.alert-info}
-Do not use `persist` for highly dynamic values that have a short life spawn.
-
-### Managing access rights to variables
-
-With `readableBy` and `writableBy`, you control who can read of write in this variable. The property accepts a string
-representing a "tag". Anyone having this "tag" can read/write in the variable.
-
-{.alert.alert-warning}
-`readableBy` and `writableBy` are specific to the "online" version of WorkAdventure because the notion of tags
-is not available unless you have an "admin" server (that is not part of the self-hosted version of WorkAdventure).
-
-Finally, the `jsonSchema` property can contain [a complete JSON schema](https://json-schema.org/) to validate the content of the variable.
-Trying to set a variable to a value that is not compatible with the schema will fail.
 
+Check the [dedicated variables page](variables.md) to learn how to declare a variable in a map.
 
 ## Tracking variables changes
 

docs/maps/variables.md

@@ -0,0 +1,59 @@
+{.section-title.accent.text-primary}
+# Variables
+
+Maps can contain **variables**. Variables are piece of information that store some data. In computer science, we like
+to say variables are storing the "state" of the room.
+
+- Variables are shared amongst all players in a given room. When the value of a variable changes for one player, it changes
+  for everyone.
+- Variables are **invisible**. There are plenty of ways they can act on the room, but by default, you don't see them.
+
+## Declaring a variable
+
+In order to declare allowed variables in a room, you need to add **objects** in an "object layer" of the map.
+
+Each object will represent a variable.
+
+<div class="row">
+    <div class="col">
+        <img src="images/object_variable.png" class="figure-img img-fluid rounded" alt="" />
+    </div>
+</div>
+
+The name of the variable is the name of the object.
+The object **type** MUST be **variable**.
+
+You can set a default value for the object in the `default` property.
+
+## Persisting variables state
+
+Use the `persist` property to save the state of the variable in database. If `persist` is false, the variable will stay
+in the memory of the WorkAdventure servers but will be wiped out of the memory as soon as the room is empty (or if the
+server restarts).
+
+{.alert.alert-info}
+Do not use `persist` for highly dynamic values that have a short life spawn.
+
+## Managing access rights to variables
+
+With `readableBy` and `writableBy`, you control who can read of write in this variable. The property accepts a string
+representing a "tag". Anyone having this "tag" can read/write in the variable.
+
+{.alert.alert-warning}
+`readableBy` and `writableBy` are specific to the "online" version of WorkAdventure because the notion of tags
+is not available unless you have an "admin" server (that is not part of the self-hosted version of WorkAdventure).
+
+In a future release, the `jsonSchema` property will contain [a complete JSON schema](https://json-schema.org/) to validate the content of the variable.
+Trying to set a variable to a value that is not compatible with the schema will fail.
+
+## Using variables
+
+There are plenty of ways to use variables in WorkAdventure:
+
+- Using the [scripting API](api-state.md), you can read, edit or track the content of variables.
+- Using the [Action zones](https://workadventu.re/map-building-extra/generic-action-zones.md), you can set the value of a variable when someone is entering or leaving a zone
+- By [binding variable values to properties in the map](https://workadventu.re/map-building-extra/variable-to-property-binding.md)
+- By [using automatically generated configuration screens](https://workadventu.re/map-building-extra/automatic-configuration.md) to create forms to edit the value of variables
+
+In general, variables can be used by third party libraries that you can embed in your map to add extra features.
+A good example of such a library is the ["Scripting API Extra" library](https://workadventu.re/map-building-extra/about.md)