diff --git a/.gitignore b/.gitignore
index c7d5284f0..bcec120a9 100644
--- a/.gitignore
+++ b/.gitignore
@@ -18,6 +18,7 @@ external_resource_packs.zip
 
 # IntelliJ
 workspace.xml
+*/workspace.xml
 
 # Temporary files
 .tmp*
diff --git a/src/net/torvald/random/FudgeDice.kt b/src/net/torvald/random/FudgeDice.kt
index c30752a1e..a72a365a8 100644
--- a/src/net/torvald/random/FudgeDice.kt
+++ b/src/net/torvald/random/FudgeDice.kt
@@ -1,6 +1,6 @@
 package net.torvald.random
 
-import java.util.Random
+import java.util.*
 
 /**
  * Created by minjaesong on 2016-02-03.
@@ -20,7 +20,7 @@ open class FudgeDice
      */
     fun roll(): Int {
         var diceResult = 0
-        for (c in 0..diceCount - 1) {
+        for (c in 0 until diceCount) {
             diceResult += rollSingleDie()
         }
 
@@ -29,12 +29,18 @@ open class FudgeDice
 
     /**
      * Roll dice and get result, for array index
-     * @return Normally distributed integer [0 , N] for N = 2 × DiceCounts + 1. 0 is the most frequent return.
+     * @return Normally distributed integer [0 , N] for N = 2 × DiceCounts + 1. (diceCount) is the most frequent return.
      */
     fun rollForArray(): Int {
         return roll() + diceCount
     }
 
+    fun <T> rollForArray(array: Array<T>): T = array[rollForArray()]
+    fun rollForArray(intArray: IntArray): Int = intArray[rollForArray()]
+    fun rollForArray(longArray: LongArray): Long = longArray[rollForArray()]
+    fun rollForArray(floatArray: FloatArray): Float = floatArray[rollForArray()]
+    fun rollForArray(doubleArray: DoubleArray): Double = doubleArray[rollForArray()]
+
     val sizeOfProbabilityRange: Int
         get() = 2 * diceCount + 1
 
diff --git a/src/net/torvald/terrarum/AppLoader.java b/src/net/torvald/terrarum/AppLoader.java
index 987dfb3dc..eec8e6b2b 100644
--- a/src/net/torvald/terrarum/AppLoader.java
+++ b/src/net/torvald/terrarum/AppLoader.java
@@ -58,7 +58,7 @@ public class AppLoader implements ApplicationListener {
      * <p>
      * e.g. 0x02010034 will be translated as 2.1.52
      */
-    public static final int VERSION_RAW = 0x00_02_04B1;
+    public static final int VERSION_RAW = 0x00_02_0590;
 
     public static final String getVERSION_STRING() {
         return String.format("%d.%d.%d", VERSION_RAW >>> 24, (VERSION_RAW & 0xff0000) >>> 16, VERSION_RAW & 0xFFFF);
@@ -596,7 +596,13 @@ public class AppLoader implements ApplicationListener {
         );
         fontSmallNumbers = TinyAlphNum.INSTANCE;
 
-        audioDevice = Gdx.audio.newAudioDevice(48000, false);
+        try {
+            audioDevice = Gdx.audio.newAudioDevice(48000, false);
+        }
+        catch (NullPointerException deviceInUse) {
+            deviceInUse.printStackTrace();
+            System.err.println("[AppLoader] failed to create audio device: Audio device occupied by Exclusive Mode Device? (e.g. ASIO4all)");
+        }
 
         // if there is a predefined screen, open that screen after my init process
         if (injectScreen != null) {
diff --git a/src/net/torvald/terrarum/itemproperties/GameItem.kt b/src/net/torvald/terrarum/itemproperties/GameItem.kt
index 1b682eefe..c8d54f26d 100644
--- a/src/net/torvald/terrarum/itemproperties/GameItem.kt
+++ b/src/net/torvald/terrarum/itemproperties/GameItem.kt
@@ -48,7 +48,7 @@ abstract class GameItem : Comparable<GameItem>, Cloneable {
 
     var nameColour = Color.WHITE
 
-    /** In kg */
+    /** In kg. Weapon with different material must have different mass. In this case, you MUST use IRON as a reference (or default) material. */
     abstract var baseMass: Double
 
     /** In kg */
diff --git a/src/net/torvald/terrarum/modulebasegame/items/WeaponMeleeCore.kt b/src/net/torvald/terrarum/modulebasegame/items/WeaponMeleeCore.kt
new file mode 100644
index 000000000..260cd4ddc
--- /dev/null
+++ b/src/net/torvald/terrarum/modulebasegame/items/WeaponMeleeCore.kt
@@ -0,0 +1,29 @@
+package net.torvald.terrarum.modulebasegame.items
+
+import net.torvald.random.Fudge3
+import net.torvald.random.HQRNG
+import net.torvald.terrarum.itemproperties.GameItem
+import net.torvald.terrarum.modulebasegame.gameactors.ActorHumanoid
+import kotlin.math.pow
+
+/**
+ * Created by minjaesong on 2019-03-17.
+ */
+object WeaponMeleeCore {
+
+    val SQRT2 = Math.sqrt(2.0)
+
+    private val dF3 = Fudge3(HQRNG())
+    private val randomiser = doubleArrayOf(0.94, 0.96, 0.98, 1.0, 1.02, 1.04, 1.06)
+
+    private fun randomise() = dF3.rollForArray(randomiser)
+    private fun getAttackMomentum(weapon: WeaponMeleeBase, actor: ActorHumanoid) =
+            weapon.mass * weapon.material.density * weapon.velocityMod * actor.scale.pow(SQRT2) // TODO multiply racial strength from RaceCodex
+    fun getAttackPower(weapon: WeaponMeleeBase, actor: ActorHumanoid, actee: ActorHumanoid) =
+            getAttackMomentum(weapon, actor) * randomise() * maxOf(1.0, (actee.hitbox.endY - actor.hitbox.startY) / actee.hitbox.height)
+
+}
+
+abstract class WeaponMeleeBase : GameItem() {
+    abstract val velocityMod: Double
+}
\ No newline at end of file
diff --git a/src/net/torvald/util/SortedArrayList.kt b/src/net/torvald/util/SortedArrayList.kt
index a49c51e0b..28a8df196 100644
--- a/src/net/torvald/util/SortedArrayList.kt
+++ b/src/net/torvald/util/SortedArrayList.kt
@@ -16,6 +16,7 @@ class SortedArrayList<T: Comparable<T>>(initialSize: Int = 10) {
      */
     fun add(elem: T) {
         // don't append-at-tail-and-sort; just insert at right index
+        // this is a modified binary search to search the right "spot" where the insert elem fits
         ReentrantLock().lock {
             var low = 0
             var high = arrayList.size
diff --git a/work_files/Attack momentum calculator.xlsx b/work_files/Attack momentum calculator.xlsx
index e8cf48424..4f0cb8437 100644
Binary files a/work_files/Attack momentum calculator.xlsx and b/work_files/Attack momentum calculator.xlsx differ