diff --git a/src/EcsWorld.cs b/src/EcsWorld.cs
index 40a345a..06923d2 100644
--- a/src/EcsWorld.cs
+++ b/src/EcsWorld.cs
@@ -189,11 +189,8 @@ namespace DCFApixels.DragonECS
         #endregion
 
         #region Entity
-        [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        public EcsSpan ToSpan()
-        {
-            return _entityDispenser.UsedToEcsSpan(id);
-        }
+        
+        #region New/Del
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public int NewEntity()
         {
@@ -201,15 +198,37 @@ namespace DCFApixels.DragonECS
             int entityID = _entityDispenser.UseFree();
             _entitiesCount++;
 
-            if (_gens.Length <= entityID)
+            if (_entitesCapacity <= entityID)
             {
                 Upsize_Internal(_gens.Length << 1);
             }
 
-            _gens[entityID] &= GEN_BITS;
+            _gens[entityID] &= GEN_MASK;
             _entityListeners.InvokeOnNewEntity(entityID);
             return entityID;
         }
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public void NewEntity(int entityID)
+        {
+#if (DEBUG && !DISABLE_DEBUG) || !DISABLE_DRAGONECS_ASSERT_CHEKS
+            if (IsUsed(entityID))
+            {
+                Throw.World_EntityIsAlreadyСontained(entityID);
+            }
+#endif
+            unchecked { _version++; }
+            _entityDispenser.Use(entityID);
+            _entitiesCount++;
+
+            if (_entitesCapacity <= entityID)
+            {
+                Upsize_Internal(_gens.Length << 1);
+            }
+
+            _gens[entityID] &= GEN_MASK;
+            _entityListeners.InvokeOnNewEntity(entityID);
+        }
+
         public entlong NewEntityLong()
         {
             int e = NewEntity();
@@ -238,6 +257,14 @@ namespace DCFApixels.DragonECS
             _entitiesCount--;
             _entityListeners.InvokeOnDelEntity(entityID);
         }
+        #endregion
+
+        #region Other
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public EcsSpan ToSpan()
+        {
+            return _entityDispenser.UsedToEcsSpan(id);
+        }
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public unsafe entlong GetEntityLong(int entityID)
         {
@@ -282,6 +309,11 @@ namespace DCFApixels.DragonECS
                 }
             }
         }
+        //public void Densify()
+        //{
+        //    _entityDispenser.Sort();
+        //}
+        #endregion
 
         #region Copy/Clone
         public void CopyEntity(int fromEntityID, int toEntityID)
@@ -374,6 +406,7 @@ namespace DCFApixels.DragonECS
                 unchecked { _gens[e]++; }//up gen
                 _gens[e] |= DEATH_GEN_BIT;
             }
+            _entityDispenser.Sort(); //уплотнение свободных айдишников
         }
         #endregion
 
diff --git a/src/EcsWorld.static.cs b/src/EcsWorld.static.cs
index 0cad189..3789982 100644
--- a/src/EcsWorld.static.cs
+++ b/src/EcsWorld.static.cs
@@ -16,7 +16,7 @@ namespace DCFApixels.DragonECS
     }
     public abstract partial class EcsWorld
     {
-        private const short GEN_BITS = 0x7fff;
+        private const short GEN_MASK = 0x7fff;
         private const short DEATH_GEN_BIT = short.MinValue;
         private const int DEL_ENT_BUFFER_SIZE_OFFSET = 5;
         private const int DEL_ENT_BUFFER_MIN_SIZE = 64;
diff --git a/src/Utils/Exceptions.cs b/src/Utils/Exceptions.cs
index a5558e2..f1fce0f 100644
--- a/src/Utils/Exceptions.cs
+++ b/src/Utils/Exceptions.cs
@@ -83,7 +83,11 @@ namespace DCFApixels.DragonECS.Internal
         {
             throw new EcsFrameworkException($"An entity with identifier {entityID} is not contained in this world");
         }
-
+        [MethodImpl(MethodImplOptions.NoInlining)]
+        public static void World_EntityIsAlreadyСontained(int entityID)
+        {
+            throw new EcsFrameworkException($"An entity with identifier {entityID} is already contained in this world");
+        }
 
         [MethodImpl(MethodImplOptions.NoInlining)]
         internal static void Ent_ThrowIsNotAlive(entlong entity)
@@ -109,7 +113,6 @@ namespace DCFApixels.DragonECS
         public EcsFrameworkException() { }
         public EcsFrameworkException(string message) : base(EcsConsts.EXCEPTION_MESSAGE_PREFIX + message) { }
         public EcsFrameworkException(string message, Exception inner) : base(EcsConsts.EXCEPTION_MESSAGE_PREFIX + message, inner) { }
-        protected EcsFrameworkException(SerializationInfo info, StreamingContext context) : base(info, context) { }
     }
     [Serializable]
     public class EcsRunnerImplementationException : EcsFrameworkException
@@ -117,6 +120,5 @@ namespace DCFApixels.DragonECS
         public EcsRunnerImplementationException() { }
         public EcsRunnerImplementationException(string message) : base(EcsConsts.EXCEPTION_MESSAGE_PREFIX + message) { }
         public EcsRunnerImplementationException(string message, Exception inner) : base(EcsConsts.EXCEPTION_MESSAGE_PREFIX + message, inner) { }
-        protected EcsRunnerImplementationException(SerializationInfo info, StreamingContext context) : base(info, context) { }
     }
 }
diff --git a/src/Utils/IdDispenser.cs b/src/Utils/IdDispenser.cs
index 5e0b476..470e10c 100644
--- a/src/Utils/IdDispenser.cs
+++ b/src/Utils/IdDispenser.cs
@@ -13,14 +13,13 @@ namespace DCFApixels.DragonECS.Utils
     {
         private const int FREE_FLAG_BIT = ~INDEX_MASK;
         private const int INDEX_MASK = 0x7FFF_FFFF;
-
         private const int MIN_SIZE = 4;
 
         private int[] _dense = Array.Empty<int>();
         private int[] _sparse = Array.Empty<int>(); //hibit free flag
 
-        private int _usedCount;     //[|uuuu|      ]
-        private int _size;          //[|uuuu|ffffff]
+        private int _usedCount;     //[uuuu|      ]
+        private int _size;          //[uuuu|ffffff]
 
         private int _nullID;
 
@@ -312,27 +311,6 @@ namespace DCFApixels.DragonECS.Utils
         }
         #endregion
 
-        #region Spans
-        public readonly struct UsedSpan : IEnumerable<int>
-        {
-            private readonly IdDispenser _instance;
-            public int Count => _instance._usedCount;
-            internal UsedSpan(IdDispenser instance) => _instance = instance;
-            public Enumerator GetEnumerator() => new Enumerator(_instance._dense, 0, _instance._usedCount);
-            IEnumerator<int> IEnumerable<int>.GetEnumerator() => GetEnumerator();
-            IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();
-        }
-        public readonly struct FreeSpan : IEnumerable<int>
-        {
-            private readonly IdDispenser _instance;
-            public int Count => _instance._size - _instance._usedCount;
-            internal FreeSpan(IdDispenser instance) => _instance = instance;
-            public Enumerator GetEnumerator() => new Enumerator(_instance._dense, _instance._usedCount, Count);
-            IEnumerator<int> IEnumerable<int>.GetEnumerator() => GetEnumerator();
-            IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();
-        }
-        #endregion
-
         #region Utils
         private enum IDState : byte
         {
@@ -340,7 +318,6 @@ namespace DCFApixels.DragonECS.Utils
             Reserved = 1,
             Used = 2,
         }
-
         private static class ThrowHalper
         {
             [MethodImpl(MethodImplOptions.NoInlining)]
@@ -361,7 +338,7 @@ namespace DCFApixels.DragonECS.Utils
             public static void UndefinedException() { throw new Exception(); }
         }
 
-        internal class DebuggerProxy
+        private class DebuggerProxy
         {
             private IdDispenser _target;
             public DebuggerProxy(IdDispenser dispenser)
@@ -370,6 +347,7 @@ namespace DCFApixels.DragonECS.Utils
             }
 #if DEBUG
             public ReadOnlySpan<int> Used => new ReadOnlySpan<int>(_target._dense, 0, _target._usedCount);
+            public ReadOnlySpan<int> Free => new ReadOnlySpan<int>(_target._dense, _target._usedCount, _target._size - _target._usedCount);
             public Pair[] Pairs
             {
                 get