diff --git a/res/graphics/fonts/numeric_small.png b/res/graphics/fonts/numeric_small.png
index 851d2bc46..0419393e7 100644
Binary files a/res/graphics/fonts/numeric_small.png and b/res/graphics/fonts/numeric_small.png differ
diff --git a/res/locales/helpOnTheFly.csv b/res/locales/helpOnTheFly.csv
index 6451a9938..27433e804 100644
--- a/res/locales/helpOnTheFly.csv
+++ b/res/locales/helpOnTheFly.csv
@@ -1,14 +1,14 @@
 "STRING_ID";"IETF language tag(s) without dash";"enUS";"frFR";"esES";"deDE";"itIT";"ptBR";"ptPT";"ruRU";"elGR";"trTR";"daDK";"noNB";"svSE";"nlNL";"plPL";"fiFI";"jaJP";"zhCN";"zhTW";"koKR";"csCZ";"huHU";"roRO";"thTH";"bgBG";"heIL";"jakanaJP";"isIC"
 
-"HELP_OTF_MAIN_1";;"Type “help slow” for the ways to make the game run faster.";"Tapez « help slow » si votre jeu fonctionne lentement.";;;;;;;;;;;;;;;;;;"게임이 느리게 돌아간다면 “help slow”를 입력해 보세요."
-"HELP_OTF_MAIN_2";;"Press PageUp/PageDown to scroll the messages.";"Appuyez sur PageUp/PageDown pour faire défiler les messages.";;;;;;;;;;;;;;;;;;"PageUp/PageDown 키를 사용해 메시지를 스크롤할 수 있습니다."
-"HELP_OTF_MAIN_3";;"Utility keys:";"Touches utilitaires:";;;;;;;;;;;;;;;;;;"기능 키:"
-"HELP_OTF_MAIN_4";;"• F3: basic information";"• F3: informations de base";;;;;;;;;;;;;;;;;;"• F3: 기본 정보"
-"HELP_OTF_MAIN_5";;"• F7: (debug) toggle light blending";"• F7: (déboguer) basculer fusion de lumière";;;;;;;;;;;;;;;;;;"• F7: (디버그용) 광원 블렌딩 켜고 끄기"
-"HELP_OTF_MAIN_6";;"• F8: toggle smooth lighting";"• F8: basculer éclairage lisse";;;;;;;;;;;;;;;;;;"• F8: 부드러운 광원 켜고 끄기"
+"HELP_OTF_MAIN_1";;"Type “help slow” for the ways to make the game run faster.";"Tapez « help slow » si votre jeu fonctionne lentement.";;;;;;;;;;;;;;;"ゲームの実行がおそければ「help slow」を入力してください。";;;"게임이 느리게 돌아간다면 “help slow”를 입력해 보세요."
+"HELP_OTF_MAIN_2";;"Press PageUp/PageDown to scroll the messages.";"Appuyez sur PageUp/PageDown pour faire défiler les messages.";;;;;;;;;;;;;;;"PageUp/PageDownを使ってメッセージのスクロールができます。";;;"PageUp/PageDown 키를 사용해 메시지를 스크롤할 수 있습니다."
+"HELP_OTF_MAIN_3";;"Utility keys:";"Touches utilitaires:";;;;;;;;;;;;;;;"技能キー";;;"기능 키:"
+"HELP_OTF_MAIN_4";;"• F3: basic information";"• F3: informations de base";;;;;;;;;;;;;;;"• F3: 基本的な情報";;;"• F3: 기본 정보"
+"HELP_OTF_MAIN_5";;"• F7: (debug) toggle light blending";"• F7: (déboguer) basculer fusion de lumière";;;;;;;;;;;;;;;"• F7: (デバッグ)光源のブレンドON/OFF";;;"• F7: (디버그용) 광원 블렌딩 켜고 끄기"
+"HELP_OTF_MAIN_6";;"• F8: toggle smooth lighting";"• F8: basculer éclairage lisse";;;;;;;;;;;;;;;"• F8: すべすべの光源ON/OFF";;;"• F8: 부드러운 광원 켜고 끄기"
 
-"HELP_OTF_SLOW_1";;"If your game runs slowly:";"Si votre jeu tourne lentement :";;;;;;;;;;;;;;;;;"";"게임이 느리게 돌아간다면"
-"HELP_OTF_SLOW_2";;"• Reset screen zoom to 1.";"• Réinitialisez le zoom de l‘écran à 1.";;;;;;;;;;;;;;;;;;"• 화면 줌을 1로 돌려주세요. "
-"HELP_OTF_SLOW_3";;"• Turn off the basic information window.";"• Désactivez la fenêtre d‘informations.";;;;;;;;;;;;;;;;;;"• 기본 정보 창을 꺼 주세요."
-"HELP_OTF_SLOW_4";;"• Turn off smooth lighting. You can do it now by pressing F8.";"• Désactivez éclairage lisse en utilisant F8.";;;;;;;;;;;;;;;;;;"• 부드러운 광원 효과를 꺼 주세요. F8을 사용할 수 있습니다."
+"HELP_OTF_SLOW_1";;"If your game runs slowly:";"Si votre jeu tourne lentement :";;;;;;;;;;;;;;;"ゲームの実行がおそければ";;;"게임이 느리게 돌아간다면"
+"HELP_OTF_SLOW_2";;"• Reset screen zoom to 1.";"• Réinitialisez le zoom de l‘écran à 1.";;;;;;;;;;;;;;;"• スクリーンのズームを1倍にリセットしてください。";;;"• 화면 줌을 1로 돌려주세요. "
+"HELP_OTF_SLOW_3";;"• Close the basic information window.";"• Désactivez la fenêtre d‘informations.";;;;;;;;;;;;;;;"• 情報ウィンドウをとじてください。";;;"• 기본 정보 창을 꺼 주세요."
+"HELP_OTF_SLOW_4";;"• Turn off smooth lighting. You can do it now by pressing F8.";"• Désactivez éclairage lisse en utilisant F8.";;;;;;;;;;;;;;;"• F8で、すべすべの光源をオフしてください。";;;"• 부드러운 광원 효과를 꺼 주세요. F8을 사용할 수 있습니다."
 
diff --git a/src/net/torvald/imagefont/GameFontBase.kt b/src/net/torvald/imagefont/GameFontBase.kt
index 1768511dd..eb92cb2f4 100644
--- a/src/net/torvald/imagefont/GameFontBase.kt
+++ b/src/net/torvald/imagefont/GameFontBase.kt
@@ -156,9 +156,7 @@ constructor() : Font {
 
     override fun getLineHeight() = H
 
-    override fun drawString(x: Float, y: Float, s: String) {
-        drawString(x, y, s, Color.white)
-    }
+    override fun drawString(x: Float, y: Float, s: String) = drawString(x, y, s, Color.white)
 
     override fun drawString(x: Float, y: Float, s: String, color: Color) {
         GL11.glEnable(GL11.GL_BLEND)
@@ -364,10 +362,13 @@ constructor() : Font {
                     )*/
                     sheetKey[prevInstance].getSubImage(sheetX, sheetY).draw(
                             Math.round(x + getWidthSubstr(s, i + 1) - glyphW).toFloat() // Interchar: pull punct right next to hangul to the left
-                            + if (i > 0 && isHangul(s[i - 1])) -3f else 0f,
+                            + if (i > 0 && isHangul(s[i - 1])) -3f
+                            else 0f,
+
                             Math.round(y).toFloat() + (if (prevInstance == SHEET_CJK_PUNCT) -1
                             else if (prevInstance == SHEET_FW_UNI) (H - H_HANGUL) / 2
                             else 0).toFloat(),
+
                             color
                     )
                 }
diff --git a/src/net/torvald/imagefont/SmallNumbers.kt b/src/net/torvald/imagefont/SmallNumbers.kt
new file mode 100644
index 000000000..a38c038e6
--- /dev/null
+++ b/src/net/torvald/imagefont/SmallNumbers.kt
@@ -0,0 +1,50 @@
+package net.torvald.imagefont
+
+import org.newdawn.slick.Color
+import org.newdawn.slick.Font
+import org.newdawn.slick.SpriteSheet
+
+/**
+ * Created by minjaesong on 16-04-15.
+ */
+class SmallNumbers : Font {
+
+    internal val fontSheet: SpriteSheet
+
+    internal val W = 8
+    internal val H = 8
+
+    private val chars = arrayOf('0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '-')
+
+    init {
+        fontSheet = SpriteSheet("./res/graphics/fonts/numeric_small.png", W, H)
+    }
+
+    override fun getHeight(str: String): Int = H
+
+    override fun getWidth(str: String): Int = str.length * W
+
+    override fun getLineHeight(): Int = H
+
+    override fun drawString(x: Float, y: Float, text: String) = drawString(x, y, text, Color.white)
+
+    override fun drawString(x: Float, y: Float, text: String, col: Color) {
+        for (i in 0..text.length - 1) {
+            val index = charToSpriteNum(text.codePointAt(i))
+            if (index != null) {
+                fontSheet.getSubImage(index, 0).draw(
+                        x + i * W, y, col
+                )
+            }
+        }
+    }
+
+    override fun drawString(x: Float, y: Float, text: String, col: Color, startIndex: Int, endIndex: Int) {
+        throw UnsupportedOperationException()
+    }
+
+    private fun charToSpriteNum(ch: Int): Int? =
+            if (ch in '0'.toInt()..'9'.toInt()) ch - '0'.toInt()
+            else if (ch == '-'.toInt())         10
+            else null
+}
\ No newline at end of file
diff --git a/src/net/torvald/terrarum/Game.kt b/src/net/torvald/terrarum/Game.kt
index 70f4bf1a2..2ec5983ce 100644
--- a/src/net/torvald/terrarum/Game.kt
+++ b/src/net/torvald/terrarum/Game.kt
@@ -172,18 +172,20 @@ constructor() : BasicGameState() {
     override fun render(gc: GameContainer, sbg: StateBasedGame, g: Graphics) {
         setBlendNormal()
 
+        // determine if lightmap blending should be done
         Terrarum.gameConfig["smoothlighting"] = KeyToggler.isOn(KEY_LIGHTMAP_SMOOTH)
 
+        // set antialias as on
         if (!g.isAntiAlias) g.isAntiAlias = true
 
         drawSkybox(g)
 
         // compensate for zoom. UIs have to be treated specially! (see UIHandler)
-        g.translate(
-                -MapCamera.cameraX * screenZoom, -MapCamera.cameraY * screenZoom)
+        g.translate(-MapCamera.cameraX * screenZoom, -MapCamera.cameraY * screenZoom)
 
         MapCamera.renderBehind(gc, g)
 
+        // draw actors
         actorContainer.forEach { actor -> if (actor is Visible) actor.drawBody(gc, g) }
         player.drawBody(gc, g)
 
@@ -201,9 +203,27 @@ constructor() : BasicGameState() {
 
         setBlendNormal()
 
+        // draw actor glows
         actorContainer.forEach { actor -> if (actor is Glowing) actor.drawGlow(gc, g) }
         player.drawGlow(gc, g)
 
+        // draw reference ID if debugWindow is open
+        if (debugWindow.isVisible) {
+            actorContainer.forEach { actor ->
+                if (actor is Visible) {
+                    g.color = Color.white
+                    g.font = Terrarum.smallNumbers
+                    g.drawString(
+                            actor.referenceID.toString(),
+                            actor.hitbox.posX,
+                            actor.hitbox.pointedY + 4
+                    )
+                    g.font = Terrarum.gameFont
+                }
+            }
+        }
+
+        // draw UIs
         uiContainer.forEach { ui -> ui.render(gc, g) }
         debugWindow.render(gc, g)
         consoleHandler.render(gc, g)
@@ -287,14 +307,14 @@ constructor() : BasicGameState() {
     /**
      * actorContainer extensions
      */
-    fun hasActor(ID: Long): Boolean {
+    fun hasActor(ID: Int): Boolean {
         for (actor in actorContainer) {
             if (actor.referenceID == ID) return true
         }
         return false
     }
 
-    fun removeActor(ID: Long) {
+    fun removeActor(ID: Int) {
         for (actor in actorContainer) {
             if (actor.referenceID == ID)
                 actorContainer.remove(actor)
@@ -307,7 +327,7 @@ constructor() : BasicGameState() {
         return true
     }
 
-    fun getActor(ID: Long): Actor {
+    fun getActor(ID: Int): Actor {
         for (actor in actorContainer) {
             if (actor.referenceID == ID)
                 return actor
diff --git a/src/net/torvald/terrarum/Terrarum.kt b/src/net/torvald/terrarum/Terrarum.kt
index 166baccd7..a7f847b2c 100644
--- a/src/net/torvald/terrarum/Terrarum.kt
+++ b/src/net/torvald/terrarum/Terrarum.kt
@@ -3,6 +3,7 @@ package net.torvald.terrarum
 import net.torvald.imagefont.GameFontWhite
 import net.torvald.JsonFetcher
 import net.torvald.JsonWriter
+import net.torvald.imagefont.SmallNumbers
 import org.lwjgl.input.Controllers
 import org.lwjgl.opengl.GL11
 import org.newdawn.slick.*
@@ -46,6 +47,7 @@ constructor(gamename: String) : StateBasedGame(gamename) {
     @Throws(SlickException::class)
     override fun initStatesList(gc: GameContainer) {
         gameFont = GameFontWhite()
+        smallNumbers = SmallNumbers()
 
         hasController = gc.input.controllerCount > 0
         if (hasController) {
@@ -100,6 +102,9 @@ constructor(gamename: String) : StateBasedGame(gamename) {
         var gameLocale = "" // locale override
 
         lateinit var gameFont: Font
+            private set
+        lateinit var smallNumbers: Font
+            private set
 
         val SCENE_ID_HOME = 1
         val SCENE_ID_GAME = 3
diff --git a/src/net/torvald/terrarum/gameactors/Actor.kt b/src/net/torvald/terrarum/gameactors/Actor.kt
index 0ced4dcac..61be521b1 100644
--- a/src/net/torvald/terrarum/gameactors/Actor.kt
+++ b/src/net/torvald/terrarum/gameactors/Actor.kt
@@ -11,9 +11,9 @@ interface Actor {
 
     /**
      * Valid RefID is equal to or greater than 32768.
-     * @return Reference ID. (32768-0x7FFF_FFFF_FFFF_FFFF)
+     * @return Reference ID. (32768-0xFFFF_FFFF)
      */
-    var referenceID: Long
+    var referenceID: Int
 
     var actorValue: ActorValue
 }
\ No newline at end of file
diff --git a/src/net/torvald/terrarum/gameactors/ActorInventory.kt b/src/net/torvald/terrarum/gameactors/ActorInventory.kt
index 39e6e7a2d..361ff3b66 100644
--- a/src/net/torvald/terrarum/gameactors/ActorInventory.kt
+++ b/src/net/torvald/terrarum/gameactors/ActorInventory.kt
@@ -23,7 +23,7 @@ class ActorInventory() {
     /**
      * <ReferenceID, Amounts>
      */
-    private val itemList: HashMap<Long, Int> = HashMap()
+    private val itemList: HashMap<Int, Int> = HashMap()
 
     /**
      * Default constructor with no encumbrance.
@@ -74,7 +74,7 @@ class ActorInventory() {
      * Get reference to the itemList
      * @return
      */
-    fun getItemList(): Map<Long, Int>? {
+    fun getItemList(): Map<Int, Int>? {
         return itemList
     }
 
@@ -83,8 +83,8 @@ class ActorInventory() {
      * @return
      */
     @Suppress("UNCHECKED_CAST")
-    fun getCopyOfItemList(): Map<Long, Int>? {
-        return itemList.clone() as Map<Long, Int>
+    fun getCopyOfItemList(): Map<Int, Int>? {
+        return itemList.clone() as Map<Int, Int>
     }
 
     fun getTotalWeight(): Float {
diff --git a/src/net/torvald/terrarum/gameactors/ActorWithBody.kt b/src/net/torvald/terrarum/gameactors/ActorWithBody.kt
index 5801efdf1..5ead41124 100644
--- a/src/net/torvald/terrarum/gameactors/ActorWithBody.kt
+++ b/src/net/torvald/terrarum/gameactors/ActorWithBody.kt
@@ -53,11 +53,11 @@ open class ActorWithBody constructor() : Actor, Visible, Glowing {
     internal var baseSpriteWidth: Int = 0
     internal var baseSpriteHeight: Int = 0
 
-    override var referenceID: Long = 0L
+    override var referenceID: Int = 0
     /**
      * Positions: top-left point
      */
-    val hitbox = Hitbox(0f,0f,0f,0f)
+    override val hitbox = Hitbox(0f,0f,0f,0f)
     @Transient val nextHitbox = Hitbox(0f,0f,0f,0f)
 
     /**
@@ -137,7 +137,7 @@ open class ActorWithBody constructor() : Actor, Visible, Glowing {
 
     init {
         do {
-            referenceID = HQRNG().nextLong() // set new ID
+            referenceID = HQRNG().nextInt() // set new ID
         } while (Terrarum.game.hasActor(referenceID)) // check for collision
 
         map = Terrarum.game.map
diff --git a/src/net/torvald/terrarum/gameactors/NPCIntelligentBase.kt b/src/net/torvald/terrarum/gameactors/NPCIntelligentBase.kt
index d39402ec4..ccf81752f 100644
--- a/src/net/torvald/terrarum/gameactors/NPCIntelligentBase.kt
+++ b/src/net/torvald/terrarum/gameactors/NPCIntelligentBase.kt
@@ -15,7 +15,7 @@ open class NPCIntelligentBase : ActorWithBody()
         , AIControlled, Pocketed, CanBeAnItem, Factionable, LandHolder {
 
     override var itemData: InventoryItem = object : InventoryItem {
-        override var itemID = HQRNG().nextLong()
+        override var itemID = HQRNG().nextInt()
 
         override var mass: Float
             get() = actorValue.get("mass") as Float
@@ -55,7 +55,7 @@ open class NPCIntelligentBase : ActorWithBody()
 
     private val factionSet = HashSet<Faction>()
 
-    override var referenceID: Long = HQRNG().nextLong()
+    override var referenceID: Int = HQRNG().nextInt()
 
     override var faction: HashSet<Faction> = HashSet()
 
diff --git a/src/net/torvald/terrarum/gameactors/Player.kt b/src/net/torvald/terrarum/gameactors/Player.kt
index 4a5cbb594..02a246f86 100644
--- a/src/net/torvald/terrarum/gameactors/Player.kt
+++ b/src/net/torvald/terrarum/gameactors/Player.kt
@@ -79,7 +79,7 @@ class Player : ActorWithBody, Controllable, Pocketed, Factionable, Luminous, Lan
         @Transient internal const val WALK_STOP_ACCEL = 0.32f
         @Transient internal const val WALK_ACCEL_BASE = 0.32f
 
-        @Transient const val PLAYER_REF_ID: Long = 0x51621D
+        @Transient const val PLAYER_REF_ID: Int = 0x51621D
         @Transient const val BASE_HEIGHT = 40
     }
 
diff --git a/src/net/torvald/terrarum/gameactors/Visible.kt b/src/net/torvald/terrarum/gameactors/Visible.kt
index 1a44d75c7..872f52771 100644
--- a/src/net/torvald/terrarum/gameactors/Visible.kt
+++ b/src/net/torvald/terrarum/gameactors/Visible.kt
@@ -7,6 +7,8 @@ import org.newdawn.slick.Graphics
  * Created by minjaesong on 16-03-14.
  */
 interface Visible {
+    val hitbox: Hitbox
+
     fun drawBody(gc: GameContainer, g: Graphics)
 
     fun updateBodySprite(gc: GameContainer, delta: Int)
diff --git a/src/net/torvald/terrarum/gameitem/InventoryItem.kt b/src/net/torvald/terrarum/gameitem/InventoryItem.kt
index beb9c98f2..a1ad61821 100644
--- a/src/net/torvald/terrarum/gameitem/InventoryItem.kt
+++ b/src/net/torvald/terrarum/gameitem/InventoryItem.kt
@@ -12,7 +12,7 @@ interface InventoryItem {
      * 4097-32767: Various items
      * >=32768: Actor RefID
      */
-    var itemID: Long
+    var itemID: Int
 
     /**
      * Weight of the item, Float
diff --git a/src/net/torvald/terrarum/gameitem/TileAsItem.kt b/src/net/torvald/terrarum/gameitem/TileAsItem.kt
index d0f7c6b79..4876c0543 100644
--- a/src/net/torvald/terrarum/gameitem/TileAsItem.kt
+++ b/src/net/torvald/terrarum/gameitem/TileAsItem.kt
@@ -8,12 +8,12 @@ import org.newdawn.slick.GameContainer
  */
 class TileAsItem(tileNum: Int) : InventoryItem {
 
-    override var itemID: Long = -1
+    override var itemID: Int = 0
     override var mass: Float = 0f
     override var scale: Float = 1f
 
     init {
-        itemID = tileNum.toLong()
+        itemID = tileNum
         mass = TilePropCodex.getProp(tileNum).density / 1000f
     }
 
diff --git a/src/net/torvald/terrarum/itemproperties/ItemPropCodex.kt b/src/net/torvald/terrarum/itemproperties/ItemPropCodex.kt
index b7271780c..029ab825b 100644
--- a/src/net/torvald/terrarum/itemproperties/ItemPropCodex.kt
+++ b/src/net/torvald/terrarum/itemproperties/ItemPropCodex.kt
@@ -29,9 +29,9 @@ object ItemPropCodex {
 
     }
 
-    fun getItem(code: Long): InventoryItem {
+    fun getItem(code: Int): InventoryItem {
         if (code < ITEM_UNIQUE_MAX)
-            return itemCodex[(code and 0xFFFFFFFF).toInt()]
+            return itemCodex[code]
         else {
             for (actor in Terrarum.game.actorContainer) {
                 if (actor is CanBeAnItem && actor.referenceID == code)