diff --git a/worldsim/src/lib.rs b/worldsim/src/lib.rs
index 5502d405b4..1d176314ff 100644
--- a/worldsim/src/lib.rs
+++ b/worldsim/src/lib.rs
@@ -2,6 +2,7 @@
 #![feature(const_generics, test)]
 #![feature(associated_type_bounds)]
 #![feature(generic_associated_types)]
+#![feature(specialization)]
 
 extern crate serde_derive;
 #[macro_use]
diff --git a/worldsim/src/lodstore/delta.rs b/worldsim/src/lodstore/delta.rs
index 4fc8f048bc..521ec1cf32 100644
--- a/worldsim/src/lodstore/delta.rs
+++ b/worldsim/src/lodstore/delta.rs
@@ -2,11 +2,13 @@ use super::data::DetailStore;
 #[allow(unused_imports)] //not unsued, cargo is just to stupud to detect that
 use super::entrylayer::EntryLayer;
 use super::layer::Layer;
+use super::layer::ParentLayer;
 use super::lodpos::LodPos;
 #[allow(unused_imports)]
 use super::materializeable::Materializeable;
 #[allow(unused_imports)]
 use super::traversable::Traversable;
+use std::slice::Iter;
 /*
     A LodDelta applies a change to a Lod
     The rules for LodDeltas are strict in order to make them as simple as possible.
@@ -21,6 +23,12 @@ use super::traversable::Traversable;
 pub trait DeltaStore: Layer {
     type DETAIL;
     fn store(&mut self, pos: LodPos, value: Option<Self::DETAIL>);
+    fn iter(&self) -> Iter<(LodPos, Option<Self::DETAIL>)>;
+}
+
+pub trait DeltaApplyer<C, D> {
+    //pub trait DeltaApplyer<COMMONDETAIL, C: DetailStore<DETAIL=COMMONDETAIL>, D: DeltaStore<DETAIL=COMMONDETAIL>> {
+    fn apply_delta(&mut self);
 }
 
 #[derive(Default, Clone)]
@@ -33,7 +41,7 @@ pub struct VecNestDelta<D: DeltaStore, T, const L: u8> {
     pub child: D,
 }
 
-pub struct DeltaWriter<'a, C: DetailStore, D: DeltaStore> {
+pub struct DeltaWriter<'a, COMMONDETAIL, C: DetailStore<DETAIL=COMMONDETAIL>, D: DeltaStore<DETAIL=COMMONDETAIL>> {
     pub delta: &'a mut D,
     pub data: &'a mut C,
 }
@@ -46,30 +54,59 @@ pub struct VecDeltaIterMut<'a, D: DeltaStore> {
     pub(super) layer: &'a mut D,
 }
 
-pub struct DataWriterIter<DT, CT> {
-    pub(super) delta_iter: DT,
+pub struct DataWriterIter<CT, DT> {
     pub(super) data_iter: CT,
+    pub(super) delta_iter: DT,
 }
 
 //#######################################################
 
-impl<'a, C: DetailStore, D: DeltaStore> DeltaWriter<'a, C, D> {
+ERROR, we want DeltaApply on delta and mut data, the Iterator is the wrong place because its only for 1 pos. the DeltaWriter is part. wrong because we only want non mut delta
+
+impl<'a, COMMONDETAIL, C: DetailStore<DETAIL=COMMONDETAIL>, D: DeltaStore<DETAIL=COMMONDETAIL>> DeltaWriter<'a, COMMONDETAIL, C, D> {
     pub fn new(delta: &'a mut D, data: &'a mut C) -> Self {
         DeltaWriter { delta, data }
     }
 }
 
+pub fn apply_delta<COMMONDETAIL, C: DetailStore<DETAIL=COMMONDETAIL>, D: DeltaStore<DETAIL=COMMONDETAIL>>(data: &mut C, delta: &D) {
+
+}
+
+impl<C, D> DeltaApplyer<C, D> for DataWriterIter<C,D> {
+    default fn apply_delta(&mut self) {
+
+    }
+}
+
+impl<COMMONDETAIL, C: DetailStore<DETAIL=COMMONDETAIL>, D: DeltaStore<DETAIL=COMMONDETAIL>> DeltaApplyer<C, D> for DataWriterIter<C,D>
+    where
+        C: ParentLayer<CHILD: DetailStore>,
+        D: ParentLayer<CHILD: DeltaStore>,
+{
+    fn apply_delta(&mut self) {
+
+    }
+}
+
+
 impl<T, const L: u8> DeltaStore for VecDelta<T, { L }> {
     type DETAIL = T;
     fn store(&mut self, pos: LodPos, value: Option<Self::DETAIL>) {
         self.detail.push((pos, value));
     }
+    fn iter(&self) -> Iter<(LodPos, Option<Self::DETAIL>)> {
+        self.detail.iter()
+    }
 }
 impl<C: DeltaStore, T, const L: u8> DeltaStore for VecNestDelta<C, T, { L }> {
     type DETAIL = T;
     fn store(&mut self, pos: LodPos, value: Option<Self::DETAIL>) {
         self.detail.push((pos, value));
     }
+    fn iter(&self) -> Iter<(LodPos, Option<Self::DETAIL>)> {
+        self.detail.iter()
+    }
 }
 
 //#######################################################
@@ -134,11 +171,11 @@ mod stests {
             assert_eq!(*w.trav_mut(i).get().get().get().mat(), 7_i8);
             w.trav_mut(i).get().get().get().store(123);
             assert_eq!(*w.trav_mut(i).get().get().get().mat(), 123_i8);
+            assert_eq!(x.detail_index.len(), 1);
             assert_eq!(d.detail.len(), 0);
             assert_eq!(d.child.detail.len(), 0);
             assert_eq!(d.child.child.detail.len(), 0);
             assert_eq!(d.child.child.child.detail.len(), 1);
-            //assert_eq!(x.detail_index.len(),1);
         }
     }
 
@@ -169,6 +206,27 @@ mod stests {
             let i = LodPos::xyz(0, 0, 0);
             assert_eq!(*w.trav_mut(i).get().get().get().mat(), 123_i8);
             assert_eq!(x.detail_index.len(), 1);
+            assert_eq!(d.child.detail.len(), 0);
+            assert_eq!(d.child.child.detail.len(), 0);
+            assert_eq!(d.child.child.child.detail.len(), 3);
+        }
+    }
+
+    #[test]
+    fn apply() {
+        let mut x = gen_simple_example();
+        let mut d = ExampleDelta::default();
+        let i = LodPos::xyz(2, 2, 2);
+        {
+            let mut w = DeltaWriter::new(&mut d, &mut x);
+            w.trav_mut(i).get().get().get().store(123);
+            assert_eq!(d.child.child.child.detail.len(), 1);
+        }
+        let mut x = gen_simple_example();
+        //assert_ne!(w.trav(i).get().get().get().mat(), 123);
+        {
+            let mut w = DeltaWriter::new(&mut d, &mut x);
+            w.trav_mut().apply_delta()
         }
     }
 
diff --git a/worldsim/src/lodstore/entrylayer.rs b/worldsim/src/lodstore/entrylayer.rs
index dc7efdefd2..004e261a10 100644
--- a/worldsim/src/lodstore/entrylayer.rs
+++ b/worldsim/src/lodstore/entrylayer.rs
@@ -50,14 +50,14 @@ impl<D: DeltaStore, T, const L: u8> VecNestDelta<D, T, { L }> {
 }
 
 impl<D: DeltaStore, C: DetailStore, T, I: ToOptionUsize, const L: u8>
-    DeltaWriter<'_, HashNestLayer<C, T, I, { L }>, VecNestDelta<D, T, { L }>>
+    DeltaWriter<'_, T, HashNestLayer<C, T, I, { L }>, VecNestDelta<D, T, { L }>>
 {
     pub fn trav<'a>(
         &'a self,
         pos: LodPos,
     ) -> DataWriterIter<
-        VecDeltaIter<'a, VecNestDelta<D, T, { L }>>,
         HashIter<'a, HashNestLayer<C, T, I, { L }>>,
+        VecDeltaIter<'a, VecNestDelta<D, T, { L }>>,
     > {
         DataWriterIter {
             delta_iter: self.delta.trav(pos),
@@ -69,8 +69,8 @@ impl<D: DeltaStore, C: DetailStore, T, I: ToOptionUsize, const L: u8>
         &'a mut self,
         pos: LodPos,
     ) -> DataWriterIter<
-        VecDeltaIterMut<'a, VecNestDelta<D, T, { L }>>,
         HashIterMut<'a, HashNestLayer<C, T, I, { L }>>,
+        VecDeltaIterMut<'a, VecNestDelta<D, T, { L }>>,
     > {
         DataWriterIter {
             delta_iter: self.delta.trav_mut(pos),
diff --git a/worldsim/src/lodstore/materializeable.rs b/worldsim/src/lodstore/materializeable.rs
index 9a0372ceee..6bdc8673db 100644
--- a/worldsim/src/lodstore/materializeable.rs
+++ b/worldsim/src/lodstore/materializeable.rs
@@ -75,8 +75,8 @@ impl<'a, L: DetailStore<KEY = usize>> Materializeable<'a> for VecIterMut<'a, L>
 
 ///////////////// delta types
 
-impl<'a, DT: Deltalizeable, CT: Materializeable<'a>> Materializeable<'a>
-    for DataWriterIter<DT, CT>
+impl<'a, CT: Materializeable<'a>, DT: Deltalizeable> Materializeable<'a>
+    for DataWriterIter<CT, DT>
 {
     type MAT_CHILD = CT::MAT_CHILD;
 
diff --git a/worldsim/src/lodstore/traversable.rs b/worldsim/src/lodstore/traversable.rs
index 0fb6fd0078..de1ed5de40 100644
--- a/worldsim/src/lodstore/traversable.rs
+++ b/worldsim/src/lodstore/traversable.rs
@@ -148,13 +148,13 @@ where
     }
 }
 
-impl<DT: Traversable, CT: Traversable> Traversable for DataWriterIter<DT, CT> {
-    type TRAV_CHILD = DataWriterIter<DT::TRAV_CHILD, CT::TRAV_CHILD>;
+impl<CT: Traversable, DT: Traversable> Traversable for DataWriterIter<CT, DT> {
+    type TRAV_CHILD = DataWriterIter<CT::TRAV_CHILD, DT::TRAV_CHILD>;
 
-    fn get(self) -> DataWriterIter<DT::TRAV_CHILD, CT::TRAV_CHILD> {
+    fn get(self) -> DataWriterIter<CT::TRAV_CHILD, DT::TRAV_CHILD> {
         DataWriterIter {
-            delta_iter: self.delta_iter.get(),
             data_iter: self.data_iter.get(),
+            delta_iter: self.delta_iter.get(),
         }
     }
 }