diff --git a/assets/img2map.py b/assets/img2map.py
index 6108e8c..ae0b775 100644
--- a/assets/img2map.py
+++ b/assets/img2map.py
@@ -27,7 +27,26 @@ elementTypes = [
     "LOCK0",
     "LOCK1",
     "LOCK2",
-    "BLOCKER"
+    "BLOCKER",
+    "",
+    "",
+    "",
+    "",
+    "",
+    "",
+    "",
+    "",
+    "",
+    "",
+    "",
+    "",
+    "MONSTER_SPIDER",
+    "MONSTER_DESTROYER",
+    "MONSTER_WARRIOR",
+    "MONSTER_PLASMABOT",
+    "MONSTER_ENDER",
+    "MONSTER_TURRET",
+    "MONSTER_EXPLODER"
   ]
 
 propertyTypes = [
diff --git a/assets/levelY.gif b/assets/levelY.gif
index a136ff7..5ea93b8 100644
Binary files a/assets/levelY.gif and b/assets/levelY.gif differ
diff --git a/levels.h b/levels.h
index 7641ff0..972b1d1 100644
--- a/levels.h
+++ b/levels.h
@@ -86,7 +86,7 @@ typedef struct
   unused because that will be used by the game engine, so the values must be
   lower than 128.
 */
-#define SFG_LEVEL_ELEMENT_NONE 255
+#define SFG_LEVEL_ELEMENT_NONE 0
 #define SFG_LEVEL_ELEMENT_BARREL 0x01
 #define SFG_LEVEL_ELEMENT_HEALTH 0x02
 #define SFG_LEVEL_ELEMENT_BULLETS 0x03
@@ -110,24 +110,24 @@ typedef struct
 #define SFG_LEVEL_ELEMENT_LOCK2 0x12
 #define SFG_LEVEL_ELEMENT_BLOCKER 0x13 ///< Invisible wall.
 
-/* 
-  Monsters have lower 4 bits zero and are only distinguished by the 4 upper
-  bits, as this is convenient for the code.
-*/
-#define SFG_LEVEL_ELEMENT_MONSTER_SPIDER 0x00
-#define SFG_LEVEL_ELEMENT_MONSTER_DESTROYER 0x10
-#define SFG_LEVEL_ELEMENT_MONSTER_WARRIOR 0x20
-#define SFG_LEVEL_ELEMENT_MONSTER_PLASMABOT 0x30
-#define SFG_LEVEL_ELEMENT_MONSTER_ENDER 0x40
-#define SFG_LEVEL_ELEMENT_MONSTER_TURRET 0x50
-#define SFG_LEVEL_ELEMENT_MONSTER_EXPLODER 0x60
+#define SFG_LEVEL_ELEMENT_MONSTER_SPIDER 0x20
+#define SFG_LEVEL_ELEMENT_MONSTER_DESTROYER 0x21
+#define SFG_LEVEL_ELEMENT_MONSTER_WARRIOR 0x22
+#define SFG_LEVEL_ELEMENT_MONSTER_PLASMABOT 0x23
+#define SFG_LEVEL_ELEMENT_MONSTER_ENDER 0x24
+#define SFG_LEVEL_ELEMENT_MONSTER_TURRET 0x25
+#define SFG_LEVEL_ELEMENT_MONSTER_EXPLODER 0x26
 
 #define SFG_MONSTERS_TOTAL 7
 
 #define SFG_MONSTER_TYPE_TO_INDEX(monsterType) \
-  ((monsterType) >> 4)
+  ((monsterType) - SFG_LEVEL_ELEMENT_MONSTER_SPIDER)
 
-#define SFG_LEVEL_ELEMENT_TYPE_IS_MOSTER(t) (((t) & 0x0f) == 0)
+#define SFG_MONSTER_INDEX_TO_TYPE(monsterIndex) \
+  ((monsterIndex) + SFG_LEVEL_ELEMENT_MONSTER_SPIDER)
+
+#define SFG_LEVEL_ELEMENT_TYPE_IS_MOSTER(t) \
+  ((t) >= SFG_LEVEL_ELEMENT_MONSTER_SPIDER)
 
 typedef struct
 {
diff --git a/main.c b/main.c
index ad5d16d..bfe564b 100755
--- a/main.c
+++ b/main.c
@@ -188,7 +188,8 @@ typedef struct
 } SFG_MonsterRecord;
 
 #define SFG_MR_STATE(mr) ((mr).stateType & SFG_MONSTER_MASK_STATE)
-#define SFG_MR_TYPE(mr) ((mr).stateType & SFG_MONSTER_MASK_TYPE)
+#define SFG_MR_TYPE(mr) \
+  (SFG_MONSTER_INDEX_TO_TYPE(((mr).stateType & SFG_MONSTER_MASK_TYPE) >> 4))
 
 #define SFG_MONSTER_COORD_TO_RCL_UNITS(c) (c * 256)
 #define SFG_MONSTER_COORD_TO_SQUARES(c) (c / 4)
@@ -1294,7 +1295,9 @@ void SFG_setAndInitLevel(const SFG_Level *level)
         monster =
         &(SFG_currentLevel.monsterRecords[SFG_currentLevel.monsterRecordCount]);
 
-        monster->stateType = e->type | SFG_MONSTER_STATE_INACTIVE;
+        monster->stateType = (SFG_MONSTER_TYPE_TO_INDEX(e->type) << 4)
+          | SFG_MONSTER_STATE_INACTIVE;
+ 
         monster->health =
           SFG_GET_MONSTER_MAX_HEALTH(SFG_MONSTER_TYPE_TO_INDEX(e->type));
 
@@ -2092,7 +2095,7 @@ void SFG_monsterPerformAI(SFG_MonsterRecord *monster)
     newPos[1] = monster->coords[1];
   }
 
-  monster->stateType = state | type;
+  monster->stateType = state | (monsterNumber << 4);
   monster->coords[0] = newPos[0];
   monster->coords[1] = newPos[1];;
 }
@@ -2449,7 +2452,9 @@ void SFG_updateLevel()
       }
       else if (monster->health == 0)
       {
-        monster->stateType = SFG_MR_TYPE(*monster) | SFG_MONSTER_STATE_DYING;
+        monster->stateType = (monster->stateType & SFG_MONSTER_MASK_TYPE) |
+          SFG_MONSTER_STATE_DYING;
+
         SFG_playSoundSafe(2,255);
       }
       else if (state != SFG_MONSTER_STATE_INACTIVE)