diff --git a/src/main/java/fr/ynerant/leveleditor/game/GameFrame.java b/src/main/java/fr/ynerant/leveleditor/game/GameFrame.java
index 2e1c889..fc78c0d 100644
--- a/src/main/java/fr/ynerant/leveleditor/game/GameFrame.java
+++ b/src/main/java/fr/ynerant/leveleditor/game/GameFrame.java
@@ -127,6 +127,7 @@ public class GameFrame extends JFrame {
         }
 
         for (Mob mob : new ArrayList<>(mobs)) {
+            getMap().getCase(mob.getX(), mob.getY()).setCollision(Collision.ANY);
             mob.tick(this);
             if (mob.getX() < 0 || mob.isDead()) {
                 mobs.remove(mob);
@@ -141,6 +142,8 @@ public class GameFrame extends JFrame {
                 else
                     reward += mob.getReward();
             }
+            else
+                getMap().getCase(mob.getX(), mob.getY()).setCollision(Collision.PARTIAL);
         }
 
         waveLabel.setText("Vague " + round);
@@ -189,6 +192,14 @@ public class GameFrame extends JFrame {
                 g.drawImage(s.getImage(), SPRITE_SIZE * tower.getX(), SPRITE_SIZE * tower.getY(), SPRITE_SIZE, SPRITE_SIZE, null, null);
             }
 
+            for (RawCase c : getMap().getCases()) {
+                if (c.getCollision() == Collision.ANY)
+                    continue;
+
+                g.setColor(new Color(0x10000000));
+                g.fillRect(SPRITE_SIZE * c.getPosX(), SPRITE_SIZE * c.getPosY(), SPRITE_SIZE, SPRITE_SIZE);
+            }
+
             repaint();
         }
 
diff --git a/src/main/java/fr/ynerant/leveleditor/game/Mob.java b/src/main/java/fr/ynerant/leveleditor/game/Mob.java
index 4f143af..34c810c 100644
--- a/src/main/java/fr/ynerant/leveleditor/game/Mob.java
+++ b/src/main/java/fr/ynerant/leveleditor/game/Mob.java
@@ -74,7 +74,6 @@ public abstract class Mob {
         else {
             tickRemains = getSlowness();
             RawCase current = game.getMap().getCase(getX(), getY());
-            current.setCollision(Collision.ANY);
 
             if (current.getPosX() == 0) {
                 move(-1, getY());
@@ -103,10 +102,7 @@ public abstract class Mob {
                     }
                 }
 
-                if (last == null) {
-                    current.setCollision(Collision.PARTIAL);
-                }
-                else {
+                if (last != null) {
                     while (pred.get(last) != current)
                         last = pred.get(last);
                     move(last.getPosX(), last.getPosY());