diff --git a/coffee/bot.coffee b/coffee/bot.coffee
index fc4a005..1dc2309 100644
--- a/coffee/bot.coffee
+++ b/coffee/bot.coffee
@@ -419,8 +419,8 @@ class Bot extends Pushable
         else
             @dir_sgn = 1
             @jump_once = false if action.id != Action.NOOP
-            log "bot.actionFinished '#{action.name}' position:", @position if action.id in [Action.FORWARD, Action.JUMP_FORWARD, Action.CLIMB_DOWN]
-            log "bot.actionFinished '#{action.name}' orientation:", @orientation.rounded().name if action.id in [Action.TURN_LEFT, Action.TURN_RIGHT, Action.CLIMB_UP]
+            # log "bot.actionFinished '#{action.name}' position:", @position if action.id in [Action.FORWARD, Action.JUMP_FORWARD, Action.CLIMB_DOWN]
+            # log "bot.actionFinished '#{action.name}' orientation:", @orientation.rounded().name if action.id in [Action.TURN_LEFT, Action.TURN_RIGHT, Action.CLIMB_UP]
             
             if world.getRealOccupantAtPos(@position.plus @getDown())?.isMutant?()
                 # keep action chain flowinwg in order to detect environment changes
diff --git a/coffee/bullet.coffee b/coffee/bullet.coffee
index 142ded0..9cfdb51 100644
--- a/coffee/bullet.coffee
+++ b/coffee/bullet.coffee
@@ -13,7 +13,7 @@ class Bullet extends Item
     
     constructor: () ->
         @size = 0.2
-        @src_object = null
+        @shooter = null
         super
         @addAction new Action @, Action.FLY,     "fly",     40
         @addAction new Action @, Action.EXPLODE, "explode", 200
@@ -21,8 +21,8 @@ class Bullet extends Item
     del: ->
         if @mesh?
             world.scene.remove @mesh
-            _.pull world.objects, @
             Timer.removeActionsOfObject @
+            _.pull world.objects, @
             @mesh = null
 
     createMesh: ->
@@ -35,7 +35,7 @@ class Bullet extends Item
         world.addObject bullet 
         bullet.direction = bot.currentDir()
         bullet.setPosition bot.position.plus bullet.direction.mul 0.8
-        bullet.src_object = bot
+        bullet.shooter = bot
         bullet.mesh.material.color.set bot.mesh.material.color
         world.playSound 'BULLET_SHOT', bot.getPos()
     
@@ -49,7 +49,7 @@ class Bullet extends Item
             @current_position = @position.plus @direction.mul relTime
         else if action.id == Action.EXPLODE
             @size = 0.2 + relTime/2.0
-            @mesh.material.opacity = 0.8 * (1.0-relTime)
+            @mesh?.material.opacity = 0.8 * (1.0-relTime)
     
     step: (step) -> 
         @mesh.position.copy @current_position
@@ -61,7 +61,7 @@ class Bullet extends Item
             
         if world.isInvalidPos(pos) or world.isOccupiedPos pos 
             hitObject = world.getRealOccupantAtPos pos 
-            if hitObject != @src_object
+            if hitObject != @shooter
                 if hitObject?
                     hitObject.bulletImpact()
                     world.playSound hitObject.bulletHitSound?() ? 'BULLET_HIT_OBJECT'
diff --git a/coffee/levels/energy.coffee b/coffee/levels/energy.coffee
index c9ea736..f4583fc 100644
--- a/coffee/levels/energy.coffee
+++ b/coffee/levels/energy.coffee
@@ -79,13 +79,13 @@ module.exports =
         
         Switch = require '../switch'
         switch1 = new Switch
-        switch1.getEventWithName("switched").addAction world.continuous (sw=switch1) -> switched sw
+        switch1.getEventWithName("switched").addAction world.continuous -> switched switch1
         switch2 = new Switch
-        switch2.getEventWithName("switched").addAction world.continuous (sw=switch2) -> switched sw
+        switch2.getEventWithName("switched").addAction world.continuous -> switched switch2
         switch3 = new Switch
-        switch3.getEventWithName("switched").addAction world.continuous (sw=switch3) -> switched sw
+        switch3.getEventWithName("switched").addAction world.continuous -> switched switch3
         switch4 = new Switch
-        switch4.getEventWithName("switched").addAction world.continuous (sw=switch4) -> switched sw
+        switch4.getEventWithName("switched").addAction world.continuous -> switched switch4
         
         world.addObjectAtPos switch1, world.decenter -s.x/2+1, 4, 0
         world.addObjectAtPos switch2, world.decenter  s.x/2, 4, 0
diff --git a/coffee/levels/sandbox.coffee b/coffee/levels/sandbox.coffee
index 7ef822b..267ebaa 100644
--- a/coffee/levels/sandbox.coffee
+++ b/coffee/levels/sandbox.coffee
@@ -30,13 +30,14 @@ module.exports =
     create: ->
         
         switched = ->
-            unoccupied = false
+            occupied = true
             for i in [3...6]
                 for j in [3...6]
-                    if world.isUnoccupiedPos i,j,0
-                        unoccupied=true
-                
-            world.toggle "exit" if not unoccupied
+                    if world.isUnoccupiedPos [i,j,0]
+                        log "isUnoccupiedPos #{i} #{j}"
+                        occupied = false
+            log "toggle? #{occupied}"    
+            world.toggle "exit" if occupied
             
         Switch = require '../switch'    
         swtch = new Switch
diff --git a/coffee/world.coffee b/coffee/world.coffee
index c49e291..6b21303 100644
--- a/coffee/world.coffee
+++ b/coffee/world.coffee
@@ -488,8 +488,8 @@ class World extends Actor
             cell.removeObject object
             if cell.isEmpty()
                 @cells[@posToIndex(pos)] = null
-        else 
-            log 'world.unsetObject [WARNING] no cell at pos:', pos
+        # else 
+            # log 'world.unsetObject [WARNING] no cell at pos:', pos
 
     newObject: (object) ->
         if _.isString object