diff --git a/src/main/java/li/cil/oc/api/API.java b/src/main/java/li/cil/oc/api/API.java
index 1b33af798..f6408a4a4 100644
--- a/src/main/java/li/cil/oc/api/API.java
+++ b/src/main/java/li/cil/oc/api/API.java
@@ -11,7 +11,7 @@ import li.cil.oc.api.detail.*;
  */
 public class API {
     public static final String ID_OWNER = "OpenComputers|Core";
-    public static final String VERSION = "4.1.0";
+    public static final String VERSION = "4.1.1";
 
     public static DriverAPI driver = null;
     public static FileSystemAPI fileSystem = null;
diff --git a/src/main/java/li/cil/oc/api/internal/Drone.java b/src/main/java/li/cil/oc/api/internal/Drone.java
index 75075500d..ee76ba2b6 100644
--- a/src/main/java/li/cil/oc/api/internal/Drone.java
+++ b/src/main/java/li/cil/oc/api/internal/Drone.java
@@ -17,7 +17,7 @@ import li.cil.oc.api.network.Environment;
  * i.e. without having to link against internal classes. This also means
  * that <em>you should not implement this</em>.
  */
-public interface Drone extends EnvironmentHost {
+public interface Drone extends EnvironmentHost, Rotatable {
     /**
      * The machine currently hosted by this drone.
      */
diff --git a/src/main/resources/assets/opencomputers/textures/entity/drone.png b/src/main/resources/assets/opencomputers/textures/entity/drone.png
deleted file mode 100644
index d26229b5c..000000000
Binary files a/src/main/resources/assets/opencomputers/textures/entity/drone.png and /dev/null differ
diff --git a/src/main/resources/assets/opencomputers/textures/model/drone.png b/src/main/resources/assets/opencomputers/textures/model/drone.png
new file mode 100644
index 000000000..f8074e3cd
Binary files /dev/null and b/src/main/resources/assets/opencomputers/textures/model/drone.png differ
diff --git a/src/main/scala/li/cil/oc/client/renderer/entity/ModelQuadcopter.scala b/src/main/scala/li/cil/oc/client/renderer/entity/ModelQuadcopter.scala
index c1cd175fa..0e7054f67 100644
--- a/src/main/scala/li/cil/oc/client/renderer/entity/ModelQuadcopter.scala
+++ b/src/main/scala/li/cil/oc/client/renderer/entity/ModelQuadcopter.scala
@@ -11,7 +11,7 @@ import net.minecraft.util.Vec3
 import org.lwjgl.opengl.GL11
 
 final class ModelQuadcopter extends ModelBase {
-  val texture = new ResourceLocation(Settings.resourceDomain, "textures/entity/drone.png")
+  val texture = new ResourceLocation(Settings.resourceDomain, "textures/model/drone.png")
 
   val body = new ModelRenderer(this, "body")
   val wing0 = new ModelRenderer(this, "wing0")
@@ -109,6 +109,15 @@ final class ModelQuadcopter extends ModelBase {
       light3.rotateAngleX = drone.flapAngles(3)(0)
       light3.rotateAngleZ = drone.flapAngles(3)(1)
 
+      // Additive blending for the lights.
+      GL11.glBlendFunc(GL11.GL_SRC_ALPHA, GL11.GL_ONE)
+      // Light color.
+      val lightColor = drone.lightColor
+      val r = ((lightColor >>> 16) & 0xFF).toByte
+      val g = ((lightColor >>> 8) & 0xFF).toByte
+      val b = ((lightColor >>> 0) & 0xFF).toByte
+      GL11.glColor3ub(r, g, b)
+
       light0.render(scale)
       light1.render(scale)
       light2.render(scale)
@@ -147,6 +156,9 @@ final class ModelQuadcopter extends ModelBase {
     light3.rotateAngleX = tilt
     light3.rotateAngleZ = -tilt
 
+    GL11.glBlendFunc(GL11.GL_SRC_ALPHA, GL11.GL_ONE)
+    GL11.glColor3ub(0x66.toByte, 0xDD.toByte, 0x55.toByte)
+
     light0.render(scale)
     light1.render(scale)
     light2.render(scale)
diff --git a/src/main/scala/li/cil/oc/common/entity/Drone.scala b/src/main/scala/li/cil/oc/common/entity/Drone.scala
index c57642e3e..5ef57c725 100644
--- a/src/main/scala/li/cil/oc/common/entity/Drone.scala
+++ b/src/main/scala/li/cil/oc/common/entity/Drone.scala
@@ -35,7 +35,10 @@ import net.minecraft.world.World
 import net.minecraft.util.EnumFacing
 import net.minecraftforge.fluids.IFluidTank
 
-class Drone(val world: World) extends Entity(world) with MachineHost with internal.Drone {
+// internal.Rotatable is also in internal.Drone, but it wasn't since the start
+// so this is to ensure it is implemented here, in the very unlikely case that
+// someone decides to ship that specific version of the API.
+class Drone(val world: World) extends Entity(world) with MachineHost with internal.Drone with internal.Rotatable {
   // Some basic constants.
   val gravity = 0.05f
   // low for slow fall (float down)
@@ -127,6 +130,14 @@ class Drone(val world: World) extends Entity(world) with MachineHost with intern
 
   // ----------------------------------------------------------------------- //
 
+  override def facing() = ForgeDirection.SOUTH
+
+  override def toLocal(value: ForgeDirection) = value
+
+  override def toGlobal(value: ForgeDirection) = value
+
+  // ----------------------------------------------------------------------- //
+
   override def cpuArchitecture = info.components.map(stack => (stack, Driver.driverFor(stack, getClass))).collectFirst {
     case (stack, driver: Processor) if driver.slot(stack) == Slot.CPU => driver.architecture(stack)
   }.orNull
@@ -185,6 +196,8 @@ class Drone(val world: World) extends Entity(world) with MachineHost with intern
     dataWatcher.addObject(10, "")
     // Inventory size for client.
     dataWatcher.addObject(11, byte2Byte(0: Byte))
+    // Light color.
+    dataWatcher.addObject(12, int2Integer(0x66DD55))
   }
 
   def initializeAfterPlacement(stack: ItemStack, player: EntityPlayer, position: Vec3) {
@@ -221,6 +234,7 @@ class Drone(val world: World) extends Entity(world) with MachineHost with intern
   def globalBufferSize = dataWatcher.getWatchableObjectInt(9)
   def statusText = dataWatcher.getWatchableObjectString(10)
   def inventorySize = dataWatcher.getWatchableObjectByte(11) & 0xFF
+  def lightColor = dataWatcher.getWatchableObjectInt(12)
 
   def setRunning(value: Boolean) = dataWatcher.updateObject(2, byte2Byte(if (value) 1: Byte else 0: Byte))
   // Round target values to low accuracy to avoid floating point errors accumulating.
@@ -233,6 +247,7 @@ class Drone(val world: World) extends Entity(world) with MachineHost with intern
   def globalBufferSize_=(value: Int) = dataWatcher.updateObject(9, int2Integer(value))
   def statusText_=(value: String) = dataWatcher.updateObject(10, Option(value).map(_.lines.map(_.take(10)).take(2).mkString("\n")).getOrElse(""))
   def inventorySize_=(value: Int) = dataWatcher.updateObject(11, byte2Byte(value.toByte))
+  def lightColor_=(value: Int) = dataWatcher.updateObject(12, int2Integer(value))
 
   @SideOnly(Side.CLIENT)
   override def func_180426_a(x: Double, y: Double, z: Double, yaw: Float, pitch: Float, data: Int, unused: Boolean) {
@@ -425,6 +440,7 @@ class Drone(val world: World) extends Entity(world) with MachineHost with intern
     selectedSlot = nbt.getByte("selectedSlot") & 0xFF
     selectedTank = nbt.getByte("selectedTank") & 0xFF
     statusText = nbt.getString("statusText")
+    lightColor = nbt.getInteger("lightColor")
   }
 
   override def writeEntityToNBT(nbt: NBTTagCompound) {
@@ -444,5 +460,6 @@ class Drone(val world: World) extends Entity(world) with MachineHost with intern
     nbt.setByte("selectedSlot", selectedSlot.toByte)
     nbt.setByte("selectedTank", selectedTank.toByte)
     nbt.setString("statusText", statusText)
+    nbt.setInteger("lightColor", lightColor)
   }
 }
diff --git a/src/main/scala/li/cil/oc/server/component/Drone.scala b/src/main/scala/li/cil/oc/server/component/Drone.scala
index 800278c73..ee9e5aa44 100644
--- a/src/main/scala/li/cil/oc/server/component/Drone.scala
+++ b/src/main/scala/li/cil/oc/server/component/Drone.scala
@@ -58,6 +58,16 @@ class Drone(val host: entity.Drone) extends prefab.ManagedEnvironment with trait
     result(host.statusText)
   }
 
+  @Callback(doc = "function():number -- Get the current color of the flap lights as an integer encoded RGB value (0xRRGGBB).")
+  def getLightColor(context: Context, args: Arguments): Array[AnyRef] = result(host.lightColor)
+
+  @Callback(doc = "function(value:number):number -- Set the color of the flap lights to the specified integer encoded RGB value (0xRRGGBB).")
+  def setLightColor(context: Context, args: Arguments): Array[AnyRef] = {
+    host.lightColor = args.checkInteger(0)
+    context.pause(0.1)
+    result(host.lightColor)
+  }
+
   // ----------------------------------------------------------------------- //
 
   @Callback(doc = "function(dx:number, dy:number, dz:number) -- Change the target position by the specified offset.")
diff --git a/src/main/scala/li/cil/oc/server/component/UpgradeInventoryController.scala b/src/main/scala/li/cil/oc/server/component/UpgradeInventoryController.scala
index 07373fc63..bf9821497 100644
--- a/src/main/scala/li/cil/oc/server/component/UpgradeInventoryController.scala
+++ b/src/main/scala/li/cil/oc/server/component/UpgradeInventoryController.scala
@@ -57,20 +57,19 @@ object UpgradeInventoryController {
 
     override def inventory = host.dynamicInventory
 
-    override def selectedSlot = host.selectedSlot
+    override def selectedSlot = host.selectedSlot - host.actualSlot(0)
 
-    override def selectedSlot_=(value: Int) = host.selectedSlot = value
+    override def selectedSlot_=(value: Int) = host.selectedSlot = host.actualSlot(value)
 
     override protected def checkSideForAction(args: Arguments, n: Int) = host.toGlobal(args.checkSideForAction(n))
 
     @Callback(doc = """function():boolean -- Swaps the equipped tool with the content of the currently selected inventory slot.""")
     def equip(context: Context, args: Arguments): Array[AnyRef] = {
-      if (host.inventorySize > 0) {
-        val selectedSlot = host.selectedSlot
+      if (inventory.getSizeInventory > 0) {
         val equipped = host.getStackInSlot(0)
-        val selected = host.getStackInSlot(selectedSlot)
+        val selected = inventory.getStackInSlot(selectedSlot)
         host.setInventorySlotContents(0, selected)
-        host.setInventorySlotContents(selectedSlot, equipped)
+        inventory.setInventorySlotContents(selectedSlot, equipped)
         result(true)
       }
       else result(false)
diff --git a/src/main/scala/li/cil/oc/server/component/traits/InventoryWorldControlMk2.scala b/src/main/scala/li/cil/oc/server/component/traits/InventoryWorldControlMk2.scala
index 1aee2f33e..f94ab65c9 100644
--- a/src/main/scala/li/cil/oc/server/component/traits/InventoryWorldControlMk2.scala
+++ b/src/main/scala/li/cil/oc/server/component/traits/InventoryWorldControlMk2.scala
@@ -25,11 +25,11 @@ trait InventoryWorldControlMk2 extends InventoryAware with WorldAware with SideR
         }
         else if (stack.stackSize == 0) {
           // Dropped whole stack.
-          inventory.setInventorySlotContents(selectedSlot, null)
+          this.inventory.setInventorySlotContents(selectedSlot, null)
         }
         else {
           // Dropped partial stack.
-          inventory.markDirty()
+          this.inventory.markDirty()
         }
 
         context.pause(Settings.get.dropDelay)