fix(sdk): add the setter for league level

Author: Julien

playground/core-concepts/core-2-game-runner.md

@@ -26,7 +26,9 @@ In addition, you will need to set **Agents** to the Game Runner. They are progra
 
 By default, you can access the game viewer for testing at [http://localhost:8888/test.html](http://localhost:8888/test.html). You may change the configuration of the game viewer by editing the `config.js` file. See the [Viewer configuration](core-4-configuration.md#viewer-configuration) for more details.
 
-Warning ⚠ To use the game viewer locally, your browser must support ES6 JavaScript **modules**. For Chrome, that's version 61 or above. For Firefox, from version 54 this feature is behind the `dom.moduleScripts.enabled` preference. To change preferences in Firefox, visit `about:config`.
+**Warning** ⚠ To use the game viewer locally, your browser must support ES6 JavaScript **modules**. For Chrome, that's version 61 or above. For Firefox, from version 54 this feature is behind the `dom.moduleScripts.enabled` preference. To change preferences in Firefox, visit `about:config`.
+
+The `MultiplayerGameRunner` also provides a `setLeagueLevel` method which you can use to test each league of your game. If left unspecified, the first level of the game will be run.
 
 
 # Examples

playground/getting-started/tutorial-2-multiplayer.md

@@ -27,9 +27,13 @@ Here's the file hierarchy for the project Tic-tac-toe:
 ```
 .
 ├── config
-│   ├── Boss.java
-│   ├── config.ini
-│   └── statement_en.html
+│   ├── Boss.java
+│   ├── config.ini
+│   ├── level1
+│   │   └── statement_en.html
+│   ├── level2
+│   │   └── statement_en.html
+│   └── stub.txt
 ├── pom.xml
 ├── README.md
 ├── src

playground/misc/misc-3-release-notes.md

@@ -7,6 +7,7 @@ The CodinGame SDK is regularly updated and improved. This document lets you know
 ### 🐞 Bug fix
 
 - `Circle` entities now displayed again
+- Included missing `setLeagueLevel` method in the `GameRunner`
 
 ## 3.4.1
 

runner/src/main/java/com/codingame/gameengine/runner/MultiplayerGameRunner.java

@@ -18,6 +18,19 @@ public MultiplayerGameRunner() {
         System.setProperty("game.mode", "multi");
     }
 
+    /**
+     * Sets the league level to run. The first league is 1.
+     * <p>The value can also be set by setting the environment variable <code>league.level</code>.</p>
+     * @param leagueLevel the league level. 1 is the lowest level and default value.
+     */
+  
+    public void setLeagueLevel(int leagueLevel) {
+      if (leagueLevel < 1 || leagueLevel >= 20) {
+        throw new IllegalArgumentException("League level must be higher than 0 and lesser than 20");
+      }
+      System.setProperty("league.level", String.valueOf(leagueLevel));
+    }
+
     /**
      * <p>
      * The seed is used to generated parameters such as width and height.<br>