Merge branch 'master' of https://github.com/teamteamteam/SpaceScooter

Conflicts:
	src/de/teamteamteam/spacescooter/gui/Credits.java

src/de/teamteamteam/spacescooter/gui/Credits.java

@@ -1,16 +1,47 @@
 package de.teamteamteam.spacescooter.gui;
 
+/**
+ * Static class accounting the credits a player earned during the game.
+ */
 public class Credits {
+	
 	/**
 	 * Credit points for the shop
 	 */
 	private static int credits = 1000;
-
+	
+	
+	/**
+	 * Private constructor.
+	 */
+	private Credits() {	}
+	
+	
+	/**
+	 * Get the current amount of credits.
+	 */
 	public static int getCredits() {
 		return credits;
 	}
 
+	/**
+	 * Set the current amount of credits.
+	 */
 	public static void setCredits(int credits) {
 		Credits.credits = credits;
 	}
+	
+	/**
+	 * Add a number of credits to the credits account.
+	 */
+	public static void add(int credits) {
+		Credits.credits += credits;
+	}
+	
+	/**
+	 * Remove a number of credits to the credits account.
+	 */
+	public static void remove(int credits) {
+		Credits.credits -= credits;
+	}
 }