it is done

core/src/mindustry/entities/units/UnitDrops.java

@@ -0,0 +1,47 @@
+package mindustry.entities.units;
+
+import arc.math.Mathf;
+import mindustry.Vars;
+import mindustry.content.Items;
+import mindustry.entities.type.BaseUnit;
+import mindustry.entities.type.TileEntity;
+import mindustry.gen.Call;
+import mindustry.type.Item;
+
+public class UnitDrops{
+    private static Item[] dropTable;
+
+    public static void dropItems(BaseUnit unit){
+        //items only dropped in waves for enemy team
+        if(unit.getTeam() != Vars.waveTeam || !Vars.state.rules.unitDrops){
+            return;
+        }
+
+        TileEntity core = unit.getClosestEnemyCore();
+
+        if(core == null || core.dst(unit) > Vars.mineTransferRange){
+            return;
+        }
+
+        if(dropTable == null){
+            dropTable = new Item[]{Items.titanium, Items.silicon, Items.lead, Items.copper};
+        }
+
+        for(int i = 0; i < 3; i++){
+            for(Item item : dropTable){
+                //only drop unlocked items
+                if(!Vars.headless && !Vars.data.isUnlocked(item)){
+                    continue;
+                }
+
+                if(Mathf.chance(0.03)){
+                    int amount = Mathf.random(20, 40);
+                    amount = core.tile.block().acceptStack(item, amount, core.tile, null);
+                    if(amount > 0){
+                        Call.transferItemTo(item, amount, unit.x + Mathf.range(2f), unit.y + Mathf.range(2f), core.tile);
+                    }
+                }
+            }
+        }
+    }
+}