diff --git a/src/edu/kit/informatik/cardgame/model/Card.java b/src/edu/kit/informatik/cardgame/model/Card.java
index bae7379..4aac4f1 100644
--- a/src/edu/kit/informatik/cardgame/model/Card.java
+++ b/src/edu/kit/informatik/cardgame/model/Card.java
@@ -1,12 +1,33 @@
 package edu.kit.informatik.cardgame.model;
 
 public enum Card {
+    /**
+     * Wood. Basic resource.
+     */
     WOOD,
+    /**
+     * Metal. Basic resource.
+     */
     METAL,
+    /**
+     * Plastic. Basic resource.
+     */
     PLASTIC,
+    /**
+     * Spider. Deadly animal.
+     */
     SPIDER,
+    /**
+     * Snake. Dangerous animal.
+     */
     SNAKE,
+    /**
+     * Tiger. Strong animal.
+     */
     TIGER,
+    /**
+     * Thunderstorm. Lifts up items and blows them away.
+     */
     THUNDERSTORM;
 
     public CardCategory category() {
@@ -22,18 +43,10 @@ public enum Card {
             case THUNDERSTORM:
                 return CardCategory.CATASTROPHE;
             default:
-                return null;
+                throw new IllegalArgumentException("no category defined for this card");
         }
     }
 
-    public boolean isResource() {
-        return this.equals(WOOD) || this.equals(METAL) || this.equals(PLASTIC);
-    }
-
-    public boolean needsDiceRoll() {
-        return this.diceSizeNeeded() > 0;
-    }
-
     public int diceSizeNeeded() {
         switch (this) {
             case SPIDER:
@@ -60,10 +73,6 @@ public enum Card {
         }
     }
 
-    public boolean isCatastrophe() {
-        return this.equals(THUNDERSTORM);
-    }
-
     public int requiredAmount() {
         switch (this) {
             case WOOD:
@@ -120,7 +129,7 @@ public enum Card {
             case THUNDERSTORM:
                 return "thunderstorm";
             default:
-                return null;
+                throw new IllegalArgumentException("toString not defined for this card value");
         }
     }
 }
diff --git a/src/edu/kit/informatik/cardgame/model/CardGame.java b/src/edu/kit/informatik/cardgame/model/CardGame.java
index dd810ff..13cbb37 100644
--- a/src/edu/kit/informatik/cardgame/model/CardGame.java
+++ b/src/edu/kit/informatik/cardgame/model/CardGame.java
@@ -58,6 +58,8 @@ public class CardGame {
                 clearResources();
                 items.remove(Item.FIREPLACE);
                 break;
+            default:
+                throw new IllegalStateException("encountered unknown card category!");
         }
         checkLost();
         return card;