diff --git a/math/radix_transform/src/main.rs b/math/radix_transform/src/main.rs
index 97aef98..9f1c050 100644
--- a/math/radix_transform/src/main.rs
+++ b/math/radix_transform/src/main.rs
@@ -5,7 +5,7 @@ use {
             ViewPort,
             TypeDict
         },
-        sequence::{VecBuffer},
+        vec::{VecBuffer},
         integer::{RadixProjection}
     }
 };
diff --git a/nested/src/core/port.rs b/nested/src/core/port.rs
index e36db56..11fbf3e 100644
--- a/nested/src/core/port.rs
+++ b/nested/src/core/port.rs
@@ -100,7 +100,7 @@ where V::Msg: Clone {
 
 impl<V: View + ?Sized> UpdateTask for ViewPort<V> where V::Msg: Clone + Send + Sync{
     fn update(&self) {
-        let mut v = {
+        let v = {
             let t = self.update_hooks.read().unwrap();
             t.iter().cloned().collect::<Vec<_>>()
         };
diff --git a/nested/src/grid/flatten.rs b/nested/src/grid/flatten.rs
index 6ba62f4..ecc6625 100644
--- a/nested/src/grid/flatten.rs
+++ b/nested/src/grid/flatten.rs
@@ -1,8 +1,7 @@
 use {
-    async_std::stream::StreamExt,
     std::{
-        sync::{Arc},
-        collections::{HashMap, HashSet}
+        sync::Arc,
+        collections::HashMap
     },
     std::sync::RwLock,
     cgmath::{Point2, Vector2},
@@ -10,7 +9,6 @@ use {
         core::{
             View, Observer, ObserverBroadcast, ObserverExt,
             ViewPort, InnerViewPort, OuterViewPort,
-            channel::{ChannelSender, ChannelReceiver},
             port::UpdateTask
         },
         grid::{GridView, GridWindowIterator},
@@ -21,7 +19,7 @@ use {
 
 impl<Item> OuterViewPort<dyn GridView<Item = OuterViewPort<dyn GridView<Item = Item>>>>
 where Item: 'static{
-    pub fn flatten(&self) -> OuterViewPort<dyn GridView<Item = Item>> {
+    pub fn flatten(&self) -> OuterViewPort<dyn GridView<Item = Item> + 'static> {
         let port = ViewPort::new();
         port.add_update_hook(Arc::new(self.0.clone()));
         Flatten::new(self.clone(), port.inner());
@@ -177,7 +175,7 @@ where Item: 'static
             }
         }
 
-        let old_limit = self.limit;
+        //let old_limit = self.limit;
         self.limit = Point2::new(
             (0 .. top_range.end.x as usize).map(|x| col_widths[x]).sum(),
             (0 .. top_range.end.y as usize).map(|y| row_heights[y]).sum()
diff --git a/nested/src/grid/offset.rs b/nested/src/grid/offset.rs
index 170a9db..bb69c7d 100644
--- a/nested/src/grid/offset.rs
+++ b/nested/src/grid/offset.rs
@@ -1,15 +1,12 @@
 use {
-    std::sync::Arc,
-    cgmath::{Point2, Vector2},
-    std::sync::RwLock,
+    cgmath::Vector2,
     crate::{
-        core::{
-            OuterViewPort
-        },
-        grid::{GridView}
+        core::OuterViewPort,
+        grid::GridView
     }
 };
 
+//<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
 
 impl<Item> OuterViewPort<dyn GridView<Item = Item>>
 where Item: 'static {
diff --git a/nested/src/integer/add.rs b/nested/src/integer/add.rs
index 49a87bf..7955dcb 100644
--- a/nested/src/integer/add.rs
+++ b/nested/src/integer/add.rs
@@ -2,7 +2,8 @@ use {
     std::sync::{Arc, RwLock},
     crate::{
         core::{InnerViewPort, OuterViewPort},
-        sequence::{SequenceView, VecBuffer},
+        sequence::SequenceView,
+        vec::VecBuffer,
         projection::ProjectionHelper
     }
 };
diff --git a/nested/src/integer/radix.rs b/nested/src/integer/radix.rs
index 3d026cb..ab99484 100644
--- a/nested/src/integer/radix.rs
+++ b/nested/src/integer/radix.rs
@@ -6,7 +6,8 @@ use {
             InnerViewPort,
             OuterViewPort
         },
-        sequence::{SequenceView, VecBuffer}
+        sequence::SequenceView,
+        vec::VecBuffer
     }
 };
 
diff --git a/nested/src/leveled_term_view.rs b/nested/src/leveled_term_view.rs
index 1f6b387..4a7d445 100644
--- a/nested/src/leveled_term_view.rs
+++ b/nested/src/leveled_term_view.rs
@@ -73,9 +73,11 @@ impl ImplIndexView for LeveledTermView {
     fn get(&self, pos: &Point2<i16>) -> Option<TerminalAtom> {
         self.src.get(pos).map(
             |a| a.add_style_front(
-                if self.level > 0 {
+                if self.level > 1 {
                     TerminalStyle::bold(true)
                         .add(TerminalStyle::bg_color((0, 0, 0)))
+                } else if self.level > 0 {
+                    TerminalStyle::bg_color((40, 40, 40))
                 } else {
                     TerminalStyle::bold(false)
                 })
diff --git a/nested/src/lib.rs b/nested/src/lib.rs
index 58f6e5e..64f83b1 100644
--- a/nested/src/lib.rs
+++ b/nested/src/lib.rs
@@ -7,6 +7,7 @@ pub mod singleton;
 pub mod index;
 pub mod grid;
 pub mod sequence;
+pub mod vec;
 pub mod terminal;
 pub mod integer;
 
diff --git a/nested/src/projection.rs b/nested/src/projection.rs
index bc0ee05..b0443c3 100644
--- a/nested/src/projection.rs
+++ b/nested/src/projection.rs
@@ -68,7 +68,7 @@ impl<P: Send + Sync + 'static> ProjectionHelper<P> {
         port.get_view_arc()
     }
 
-    pub fn new_index_arg<Key: Hash + Eq + Clone + Send + Sync + 'static, Item: 'static>(
+    pub fn new_index_arg<Key: Hash + Eq + Clone + Send + Sync + std::fmt::Debug + 'static, Item: 'static>(
         &mut self,
         port: OuterViewPort<dyn IndexView<Key, Item = Item>>,
         notify: impl Fn(&mut P, &Key) + Send + Sync + 'static
@@ -87,7 +87,7 @@ impl<P: Send + Sync + 'static> ProjectionHelper<P> {
         (tx, rx): (ChannelSender<D>, ChannelReceiver<D>)
     )
         -> Arc<RwLock<ProjectionArg<P, V, D>>>
-    where V::Msg: Send + Sync,
+    where V::Msg: Send + Sync + std::fmt::Debug,
           D::IntoIter: Send + Sync + 'static
     {
         let arg = Arc::new(RwLock::new(
@@ -124,18 +124,22 @@ impl<P, V, D> UpdateTask for ProjectionArg<P, V, D>
 where P: Send + Sync + 'static,
       V: View + ?Sized,
       D: ChannelData<Item = V::Msg>,
-      D::IntoIter: Send + Sync
+      D::IntoIter: Send + Sync,
+V::Msg: std::fmt::Debug
 {
     fn update(&self) {
         if let Some(p) = self.proj.read().unwrap().upgrade() {
             if let Some(data) = self.rx.try_recv() {
                 for msg in data {
+                    //eprintln!("proj update {:?}", msg);
                     (self.notify)(
                         &mut *p.write().unwrap(),
                         &msg
                     );
                 }
             }
+        } else {
+            eprintln!("proj update: upgrade fail");
         }
     }
 }
@@ -144,7 +148,8 @@ impl<P, V, D> UpdateTask for RwLock<ProjectionArg<P, V, D>>
 where P: Send + Sync + 'static,
       V: View + ?Sized,
       D: ChannelData<Item = V::Msg>,
-      D::IntoIter: Send + Sync
+      D::IntoIter: Send + Sync,
+V::Msg: std::fmt::Debug
 {
     fn update(&self) {
         self.read().unwrap().update();
diff --git a/nested/src/sequence/flatten.rs b/nested/src/sequence/flatten.rs
index e2383fe..e317b8f 100644
--- a/nested/src/sequence/flatten.rs
+++ b/nested/src/sequence/flatten.rs
@@ -1,15 +1,13 @@
 use {
-    async_std::stream::StreamExt,
     std::{
-        sync::{Arc},
-        collections::{BTreeMap, HashSet}
+        sync::Arc,
+        collections::BTreeMap
     },
     std::sync::RwLock,
     crate::{
         core::{
             View, Observer, ObserverBroadcast, ObserverExt,
             ViewPort, InnerViewPort, OuterViewPort,
-            channel::{ChannelSender, ChannelReceiver},
             port::UpdateTask
         },
         sequence::SequenceView,
@@ -144,7 +142,7 @@ where Item: 'static
         let mut dirty_idx = Vec::new();
         let mut cur_offset = 0;
 
-        for (chunk_idx, chunk) in self.chunks.iter_mut() {
+        for (_chunk_idx, chunk) in self.chunks.iter_mut() {
             let old_offset = chunk.offset;
             chunk.offset = cur_offset;
             chunk.len = chunk.view.len().unwrap_or(0);
diff --git a/nested/src/sequence/mod.rs b/nested/src/sequence/mod.rs
index eb1d9a0..42f7f9e 100644
--- a/nested/src/sequence/mod.rs
+++ b/nested/src/sequence/mod.rs
@@ -1,14 +1,10 @@
 
 pub mod seq2idx;
-pub mod vec_buffer;
 pub mod map;
 pub mod filter;
 pub mod flatten;
 
-pub use {
-    seq2idx::{Sequence2Index},
-    vec_buffer::{VecBuffer, VecSequence}
-};
+pub use seq2idx::{Sequence2Index};
 
 //<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
 
diff --git a/nested/src/sequence/vec_buffer.rs b/nested/src/sequence/vec_buffer.rs
deleted file mode 100644
index 2d3c9e8..0000000
--- a/nested/src/sequence/vec_buffer.rs
+++ /dev/null
@@ -1,362 +0,0 @@
-use {
-    std::{
-        sync::Arc,
-        ops::{Deref, DerefMut},
-        io::Write
-    },
-    std::sync::RwLock,
-    async_std::{
-        io::{Read, ReadExt},
-        stream::{StreamExt}
-    },
-    serde::{Serialize, Deserialize, de::DeserializeOwned},
-    crate::{
-        core::{View, Observer, ObserverExt, ObserverBroadcast, ViewPort, InnerViewPort, OuterViewPort},
-        sequence::SequenceView,
-    }
-};
-
-#[derive(Clone, Serialize, Deserialize)]
-pub enum VecDiff<T> {
-    Clear,
-    Push(T),
-    Remove(usize),
-    Insert{ idx: usize, val: T },
-    Update{ idx: usize, val: T }
-}
-
-//<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
-
-impl<T> View for Vec<T>
-where T: Clone + Send + Sync + 'static {
-    type Msg = VecDiff<T>;
-}
-
-//<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
-
-/// Adapter View implementing `Sequence` for `Vec`
-pub struct VecSequence<T>
-where T: Clone + Send + Sync + 'static {
-    cur_len: usize,
-    data: Option<Arc<RwLock<Vec<T>>>>,
-    cast: Arc<RwLock<ObserverBroadcast<dyn SequenceView<Item = T>>>>
-}
-
-/// Serialization Observer for `Vec`
-pub struct VecBinWriter<T, W>
-where T: Clone + Send + Sync + 'static,
-      W: Write + Send + Sync {
-    data: Option<Arc<RwLock<Vec<T>>>>,
-    out: RwLock<W>
-}
-
-pub struct VecJsonWriter<T, W>
-where T: Clone + Send + Sync + 'static,
-      W: Write + Send + Sync {
-    data: Option<Arc<RwLock<Vec<T>>>>,
-    out: RwLock<W>
-}
-
-impl<T> OuterViewPort<RwLock<Vec<T>>>
-where T: Clone + Send + Sync + 'static {
-    pub fn to_sequence(&self) -> OuterViewPort<dyn SequenceView<Item = T>> {
-        let port = ViewPort::new();
-        port.add_update_hook(Arc::new(self.0.clone()));
-
-        let vec_seq = VecSequence::new(port.inner());
-        self.add_observer(vec_seq.clone());
-        port.into_outer()
-    }
-}
-
-impl<T> OuterViewPort<RwLock<Vec<T>>>
-where T: Clone + Serialize + Send + Sync + 'static {
-    pub fn serialize_bin<W: Write + Send + Sync + 'static>(&self, out: W) -> Arc<RwLock<VecBinWriter<T, W>>> {
-        let writer = Arc::new(RwLock::new(
-            VecBinWriter {
-                data: None,
-                out: RwLock::new(out),
-            }
-        ));
-        self.add_observer(writer.clone());
-        writer
-    }
-
-    pub fn serialize_json<W: Write + Send + Sync + 'static>(&self, out: W) -> Arc<RwLock<VecJsonWriter<T, W>>> {
-        let writer = Arc::new(RwLock::new(
-            VecJsonWriter {
-                data: None,
-                out: RwLock::new(out),
-            }
-        ));
-        self.add_observer(writer.clone());
-        writer
-    }
-}
-
-
-impl<T, W> Observer<RwLock<Vec<T>>> for VecBinWriter<T, W>
-where T: Clone + Serialize + Send + Sync + 'static,
-      W: Write + Send + Sync
-{
-    fn reset(&mut self, view: Option<Arc<RwLock<Vec<T>>>>) {
-        self.data = view;
-        let mut out = self.out.write().unwrap();
-
-        out.write(&bincode::serialized_size(&VecDiff::<T>::Clear).unwrap().to_le_bytes()).expect("");
-        out.write(&bincode::serialize(&VecDiff::<T>::Clear).unwrap()).expect("");
-
-        if let Some(data) = self.data.as_ref() {
-            for x in data.read().unwrap().iter() {
-                out.write(&bincode::serialized_size(&VecDiff::Push(x)).unwrap().to_le_bytes()).expect("");
-                out.write(&bincode::serialize(&VecDiff::Push(x)).unwrap()).expect("");
-            }
-        }
-
-        out.flush().expect("");
-    }
-
-    fn notify(&mut self, diff: &VecDiff<T>) {
-        let mut out = self.out.write().unwrap();
-        out.write(&bincode::serialized_size(diff).unwrap().to_le_bytes()).expect("");
-        out.write(&bincode::serialize(diff).unwrap()).expect("");
-        out.flush().expect("");
-    }
-}
-
-impl<T, W> Observer<RwLock<Vec<T>>> for VecJsonWriter<T, W>
-where T: Clone + Serialize + Send + Sync + 'static,
-      W: Write + Send + Sync
-{
-    fn reset(&mut self, view: Option<Arc<RwLock<Vec<T>>>>) {
-        self.data = view;
-
-        self.out.write().unwrap().write(&serde_json::to_string(&VecDiff::<T>::Clear).unwrap().as_bytes()).expect("");
-        self.out.write().unwrap().write(b"\n").expect("");
-
-        if let Some(data) = self.data.as_ref() {
-            for x in data.read().unwrap().iter() {
-                self.out.write().unwrap().write(&serde_json::to_string(&VecDiff::Push(x)).unwrap().as_bytes()).expect("");
-                self.out.write().unwrap().write(b"\n").expect("");
-            }
-        }
-
-        self.out.write().unwrap().flush().expect("");
-    }
-
-    fn notify(&mut self, diff: &VecDiff<T>) {
-        self.out.write().unwrap().write(serde_json::to_string(diff).unwrap().as_bytes()).expect("");
-        self.out.write().unwrap().write(b"\n").expect("");
-        self.out.write().unwrap().flush().expect("");
-    }
-}
-
-impl<T> VecSequence<T>
-where T: Clone + Send + Sync + 'static {
-    pub fn new(
-        port: InnerViewPort<dyn SequenceView<Item = T>>
-    ) -> Arc<RwLock<Self>> {
-        let seq = Arc::new(RwLock::new(
-            VecSequence {
-                cur_len: 0,
-                data: None,
-                cast: port.get_broadcast()
-            }
-        ));
-        port.set_view(Some(seq.clone()));
-        seq
-    }
-}
-
-impl<T> Observer<RwLock<Vec<T>>> for VecSequence<T>
-where T: Clone + Send + Sync + 'static {
-    fn reset(&mut self, view: Option<Arc<RwLock<Vec<T>>>>) {
-        let old_len = self.cur_len;
-        self.data = view;
-        self.cur_len =
-            if let Some(data) = self.data.as_ref() {
-                data.read().unwrap().len()
-            } else {
-                0
-            };
-
-        self.cast.notify_each(0 .. std::cmp::max(old_len, self.cur_len));
-    }
-
-    fn notify(&mut self, diff: &VecDiff<T>) {
-        match diff {
-            VecDiff::Clear => {
-                self.cast.notify_each(0 .. self.cur_len);
-                self.cur_len = 0
-            },
-            VecDiff::Push(_) => {
-                self.cast.notify(&self.cur_len);
-                self.cur_len += 1;
-            },
-            VecDiff::Remove(idx) => {
-                self.cast.notify_each(*idx .. self.cur_len);
-                self.cur_len -= 1;
-            },
-            VecDiff::Insert{ idx, val: _ } => {
-                self.cur_len += 1;
-                self.cast.notify_each(*idx .. self.cur_len);
-            },
-            VecDiff::Update{ idx, val: _ } => {
-                self.cast.notify(&idx);
-            }
-        }
-    }
-}
-
-impl<T> View for VecSequence<T>
-where T: Clone + Send + Sync + 'static {
-    type Msg = usize;
-}
-
-impl<T> SequenceView for VecSequence<T>
-where T: Clone + Send + Sync + 'static {
-    type Item = T;
-
-    fn get(&self, idx: &usize) -> Option<T> {
-        self.data.as_ref()?
-            .read().unwrap()
-            .get(*idx).cloned()
-    }
-
-    fn len(&self) -> Option<usize> {
-        Some(self.cur_len)
-    }
-}
-
-//<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
-
-#[derive(Clone)]
-pub struct VecBuffer<T>
-where T: Clone + Send + Sync + 'static
-{
-    data: Arc<RwLock<Vec<T>>>,
-    cast: Arc<RwLock<ObserverBroadcast<RwLock<Vec<T>>>>>
-}
-
-impl<T> VecBuffer<T>
-where T: DeserializeOwned + Clone + Send + Sync + 'static
-{
-    pub async fn from_json<R: Read + async_std::io::Read + Unpin>(&mut self, read: R) {
-        let mut bytes = read.bytes();
-        let mut s = String::new();
-        while let Some(Ok(b)) = bytes.next().await {
-            match b {
-                b'\n' => {
-                    if s.len() > 0 {
-                        let diff = serde_json::from_str::<VecDiff<T>>(&s).expect("error parsing json");
-                        self.apply_diff(diff);
-                        s.clear();
-                    }
-                },
-                c => {
-                    s.push(c as char);
-                }
-            }
-        }
-    }
-}
-
-impl<T> VecBuffer<T>
-where T: Clone + Send + Sync + 'static
-{
-    pub fn with_data(
-        data: Vec<T>,
-        port: InnerViewPort<RwLock<Vec<T>>>
-    ) -> Self {
-        let data = Arc::new(RwLock::new(data));
-        port.set_view(Some(data.clone()));
-        VecBuffer { data, cast: port.get_broadcast() }
-    }
-
-    pub fn new(port: InnerViewPort<RwLock<Vec<T>>>) -> Self {
-        VecBuffer::with_data(Vec::new(), port)
-    }
-
-    pub fn apply_diff(&mut self, diff: VecDiff<T>) {
-        let mut data = self.data.write().unwrap();
-        match &diff {
-            VecDiff::Clear => { data.clear(); },
-            VecDiff::Push(val) => { data.push(val.clone()); },
-            VecDiff::Remove(idx) => { data.remove(*idx); },
-            VecDiff::Insert{ idx, val } => { data.insert(*idx, val.clone()); },
-            VecDiff::Update{ idx, val } => { data[*idx] = val.clone(); }
-        }
-        drop(data);
-
-        self.cast.notify(&diff);
-    }
-
-    pub fn len(&self) -> usize {
-        self.data.read().unwrap().len()
-    }
-
-    pub fn get(&self, idx: usize) -> T {
-        self.data.read().unwrap()[idx].clone()
-    }
-
-    pub fn clear(&mut self) {
-        self.apply_diff(VecDiff::Clear);
-    }
-
-    pub fn push(&mut self, val: T) {
-        self.apply_diff(VecDiff::Push(val));
-    }
-
-    pub fn remove(&mut self, idx: usize) {
-        self.apply_diff(VecDiff::Remove(idx));
-    }
-
-    pub fn insert(&mut self, idx: usize, val: T) {
-        self.apply_diff(VecDiff::Insert{ idx, val });
-    }
-
-    pub fn update(&mut self, idx: usize, val: T) {
-        self.apply_diff(VecDiff::Update{ idx, val });
-    }
-
-    pub fn get_mut(&mut self, idx: usize) -> MutableVecAccess<T> {
-        MutableVecAccess {
-            buf: self.clone(),
-            idx,
-            val: self.get(idx)
-        }
-    }
-}
-
-//<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
-
-pub struct MutableVecAccess<T>
-where T: Clone + Send + Sync + 'static {
-    buf: VecBuffer<T>,
-    idx: usize,
-    val: T,
-}
-
-impl<T> Deref for MutableVecAccess<T>
-where T: Clone + Send + Sync + 'static {
-    type Target = T;
-
-    fn deref(&self) -> &T {
-        &self.val
-    }
-}
-
-impl<T> DerefMut for MutableVecAccess<T>
-where T: Clone + Send + Sync + 'static {
-    fn deref_mut(&mut self) -> &mut Self::Target {
-        &mut self.val
-    }
-}
-
-impl<T> Drop for MutableVecAccess<T>
-where T: Clone + Send + Sync + 'static {
-    fn drop(&mut self) {
-        self.buf.update(self.idx, self.val.clone());
-    }
-}
-
diff --git a/nested/src/string_editor.rs b/nested/src/string_editor.rs
index 064671e..8f9d070 100644
--- a/nested/src/string_editor.rs
+++ b/nested/src/string_editor.rs
@@ -3,7 +3,7 @@ use {
     crate::{
         core::{ViewPort, OuterViewPort},
         singleton::{SingletonView, SingletonBuffer},
-        sequence::VecBuffer,
+        vec::VecBuffer,
         terminal::{TerminalView}
     }
 };
diff --git a/nested/src/terminal/mod.rs b/nested/src/terminal/mod.rs
index 587a9f2..2687a92 100644
--- a/nested/src/terminal/mod.rs
+++ b/nested/src/terminal/mod.rs
@@ -24,7 +24,7 @@ pub trait TerminalView = GridView<Item = TerminalAtom>;
 
 use {
     crate::{
-        sequence::VecBuffer,
+        vec::VecBuffer,
         core::{ViewPort, OuterViewPort}
     },
     cgmath::Point2
@@ -32,7 +32,7 @@ use {
 
 pub fn make_label(s: &str) -> OuterViewPort<dyn TerminalView> {
     let label_port = ViewPort::new();
-    let label = VecBuffer::with_data(s.chars().collect(), label_port.inner());
+    let _label = VecBuffer::with_data(s.chars().collect(), label_port.inner());
     label_port.outer()
         .to_sequence()
         .map(|c| TerminalAtom::from(c))
diff --git a/nested/src/vec/buffer.rs b/nested/src/vec/buffer.rs
new file mode 100644
index 0000000..5116550
--- /dev/null
+++ b/nested/src/vec/buffer.rs
@@ -0,0 +1,129 @@
+use {
+    std::{
+        sync::Arc,
+        ops::{Deref, DerefMut},
+    },
+    std::sync::RwLock,
+    crate::{
+        core::{View, Observer, ObserverBroadcast, InnerViewPort},
+        vec::VecDiff
+    }
+};
+
+//<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
+
+impl<T> View for Vec<T>
+where T: Clone + Send + Sync + 'static {
+    type Msg = VecDiff<T>;
+}
+
+//<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
+
+#[derive(Clone)]
+pub struct VecBuffer<T>
+where T: Clone + Send + Sync + 'static
+{
+    data: Arc<RwLock<Vec<T>>>,
+    cast: Arc<RwLock<ObserverBroadcast<RwLock<Vec<T>>>>>
+}
+
+impl<T> VecBuffer<T>
+where T: Clone + Send + Sync + 'static
+{
+    pub fn with_data(
+        data: Vec<T>,
+        port: InnerViewPort<RwLock<Vec<T>>>
+    ) -> Self {
+        let data = Arc::new(RwLock::new(data));
+        port.set_view(Some(data.clone()));
+        VecBuffer { data, cast: port.get_broadcast() }
+    }
+
+    pub fn new(port: InnerViewPort<RwLock<Vec<T>>>) -> Self {
+        VecBuffer::with_data(Vec::new(), port)
+    }
+
+    pub fn apply_diff(&mut self, diff: VecDiff<T>) {
+        let mut data = self.data.write().unwrap();
+        match &diff {
+            VecDiff::Clear => { data.clear(); },
+            VecDiff::Push(val) => { data.push(val.clone()); },
+            VecDiff::Remove(idx) => { data.remove(*idx); },
+            VecDiff::Insert{ idx, val } => { data.insert(*idx, val.clone()); },
+            VecDiff::Update{ idx, val } => { data[*idx] = val.clone(); }
+        }
+        drop(data);
+
+        self.cast.notify(&diff);
+    }
+
+    pub fn len(&self) -> usize {
+        self.data.read().unwrap().len()
+    }
+
+    pub fn get(&self, idx: usize) -> T {
+        self.data.read().unwrap()[idx].clone()
+    }
+
+    pub fn clear(&mut self) {
+        self.apply_diff(VecDiff::Clear);
+    }
+
+    pub fn push(&mut self, val: T) {
+        self.apply_diff(VecDiff::Push(val));
+    }
+
+    pub fn remove(&mut self, idx: usize) {
+        self.apply_diff(VecDiff::Remove(idx));
+    }
+
+    pub fn insert(&mut self, idx: usize, val: T) {
+        self.apply_diff(VecDiff::Insert{ idx, val });
+    }
+
+    pub fn update(&mut self, idx: usize, val: T) {
+        self.apply_diff(VecDiff::Update{ idx, val });
+    }
+
+    pub fn get_mut(&mut self, idx: usize) -> MutableVecAccess<T> {
+        MutableVecAccess {
+            buf: self.clone(),
+            idx,
+            val: self.get(idx)
+        }
+    }
+}
+
+//<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
+
+pub struct MutableVecAccess<T>
+where T: Clone + Send + Sync + 'static {
+    buf: VecBuffer<T>,
+    idx: usize,
+    val: T,
+}
+
+impl<T> Deref for MutableVecAccess<T>
+where T: Clone + Send + Sync + 'static {
+    type Target = T;
+
+    fn deref(&self) -> &T {
+        &self.val
+    }
+}
+
+impl<T> DerefMut for MutableVecAccess<T>
+where T: Clone + Send + Sync + 'static {
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        &mut self.val
+    }
+}
+
+impl<T> Drop for MutableVecAccess<T>
+where T: Clone + Send + Sync + 'static {
+    fn drop(&mut self) {
+        self.buf.update(self.idx, self.val.clone());
+    }
+}
+
+
diff --git a/nested/src/vec/mod.rs b/nested/src/vec/mod.rs
new file mode 100644
index 0000000..0311a3b
--- /dev/null
+++ b/nested/src/vec/mod.rs
@@ -0,0 +1,25 @@
+
+pub mod buffer;
+pub mod vec2seq;
+pub mod vec2json;
+pub mod vec2bin;
+
+pub use {
+    buffer::VecBuffer
+};
+
+//<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
+
+use {
+    serde::{Serialize, Deserialize}
+};
+
+#[derive(Clone, Serialize, Deserialize)]
+pub enum VecDiff<T> {
+    Clear,
+    Push(T),
+    Remove(usize),
+    Insert{ idx: usize, val: T },
+    Update{ idx: usize, val: T }
+}
+
diff --git a/nested/src/vec/vec2bin.rs b/nested/src/vec/vec2bin.rs
new file mode 100644
index 0000000..c274324
--- /dev/null
+++ b/nested/src/vec/vec2bin.rs
@@ -0,0 +1,67 @@
+use {
+    std::{
+        sync::Arc,
+        io::Write
+    },
+    std::sync::RwLock,
+    serde::Serialize,
+    crate::{
+        core::{Observer, OuterViewPort},
+        vec::VecDiff
+    }
+};
+
+//<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
+
+/// Serialization Observer for `Vec`
+pub struct VecBinWriter<T, W>
+where T: Clone + Send + Sync + 'static,
+      W: Write + Send + Sync {
+    data: Option<Arc<RwLock<Vec<T>>>>,
+    out: RwLock<W>
+}
+
+
+impl<T> OuterViewPort<RwLock<Vec<T>>>
+where T: Clone + Serialize + Send + Sync + 'static {
+    pub fn serialize_bin<W: Write + Send + Sync + 'static>(&self, out: W) -> Arc<RwLock<VecBinWriter<T, W>>> {
+        let writer = Arc::new(RwLock::new(
+            VecBinWriter {
+                data: None,
+                out: RwLock::new(out),
+            }
+        ));
+        self.add_observer(writer.clone());
+        writer
+    }
+}
+
+impl<T, W> Observer<RwLock<Vec<T>>> for VecBinWriter<T, W>
+where T: Clone + Serialize + Send + Sync + 'static,
+      W: Write + Send + Sync
+{
+    fn reset(&mut self, view: Option<Arc<RwLock<Vec<T>>>>) {
+        self.data = view;
+        let mut out = self.out.write().unwrap();
+
+        out.write(&bincode::serialized_size(&VecDiff::<T>::Clear).unwrap().to_le_bytes()).expect("");
+        out.write(&bincode::serialize(&VecDiff::<T>::Clear).unwrap()).expect("");
+
+        if let Some(data) = self.data.as_ref() {
+            for x in data.read().unwrap().iter() {
+                out.write(&bincode::serialized_size(&VecDiff::Push(x)).unwrap().to_le_bytes()).expect("");
+                out.write(&bincode::serialize(&VecDiff::Push(x)).unwrap()).expect("");
+            }
+        }
+
+        out.flush().expect("");
+    }
+
+    fn notify(&mut self, diff: &VecDiff<T>) {
+        let mut out = self.out.write().unwrap();
+        out.write(&bincode::serialized_size(diff).unwrap().to_le_bytes()).expect("");
+        out.write(&bincode::serialize(diff).unwrap()).expect("");
+        out.flush().expect("");
+    }
+}
+
diff --git a/nested/src/vec/vec2json.rs b/nested/src/vec/vec2json.rs
new file mode 100644
index 0000000..b5c8a0f
--- /dev/null
+++ b/nested/src/vec/vec2json.rs
@@ -0,0 +1,91 @@
+use {
+    std::{
+        sync::Arc,
+        io::Write
+    },
+    std::sync::RwLock,
+    async_std::{
+        io::{Read, ReadExt},
+        stream::{StreamExt}
+    },
+    serde::{Serialize, de::DeserializeOwned},
+    crate::{
+        core::{Observer, OuterViewPort},
+        vec::{VecDiff, VecBuffer}
+    }
+};
+
+//<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
+
+pub struct VecJsonWriter<T, W>
+where T: Clone + Send + Sync + 'static,
+      W: Write + Send + Sync {
+    data: Option<Arc<RwLock<Vec<T>>>>,
+    out: RwLock<W>
+}
+
+impl<T> OuterViewPort<RwLock<Vec<T>>>
+where T: Clone + Serialize + Send + Sync + 'static {
+    pub fn serialize_json<W: Write + Send + Sync + 'static>(&self, out: W) -> Arc<RwLock<VecJsonWriter<T, W>>> {
+        let writer = Arc::new(RwLock::new(
+            VecJsonWriter {
+                data: None,
+                out: RwLock::new(out),
+            }
+        ));
+        self.add_observer(writer.clone());
+        writer
+    }
+}
+
+impl<T, W> Observer<RwLock<Vec<T>>> for VecJsonWriter<T, W>
+where T: Clone + Serialize + Send + Sync + 'static,
+      W: Write + Send + Sync
+{
+    fn reset(&mut self, view: Option<Arc<RwLock<Vec<T>>>>) {
+        self.data = view;
+
+        self.out.write().unwrap().write(&serde_json::to_string(&VecDiff::<T>::Clear).unwrap().as_bytes()).expect("");
+        self.out.write().unwrap().write(b"\n").expect("");
+
+        if let Some(data) = self.data.as_ref() {
+            for x in data.read().unwrap().iter() {
+                self.out.write().unwrap().write(&serde_json::to_string(&VecDiff::Push(x)).unwrap().as_bytes()).expect("");
+                self.out.write().unwrap().write(b"\n").expect("");
+            }
+        }
+
+        self.out.write().unwrap().flush().expect("");
+    }
+
+    fn notify(&mut self, diff: &VecDiff<T>) {
+        self.out.write().unwrap().write(serde_json::to_string(diff).unwrap().as_bytes()).expect("");
+        self.out.write().unwrap().write(b"\n").expect("");
+        self.out.write().unwrap().flush().expect("");
+    }
+}
+
+impl<T> VecBuffer<T>
+where T: DeserializeOwned + Clone + Send + Sync + 'static
+{
+    pub async fn from_json<R: Read + async_std::io::Read + Unpin>(&mut self, read: R) {
+        let mut bytes = read.bytes();
+        let mut s = String::new();
+        while let Some(Ok(b)) = bytes.next().await {
+            match b {
+                b'\n' => {
+                    if s.len() > 0 {
+                        let diff = serde_json::from_str::<VecDiff<T>>(&s).expect("error parsing json");
+                        self.apply_diff(diff);
+                        s.clear();
+                    }
+                },
+                c => {
+                    s.push(c as char);
+                }
+            }
+        }
+    }
+}
+
+
diff --git a/nested/src/vec/vec2seq.rs b/nested/src/vec/vec2seq.rs
new file mode 100644
index 0000000..0c8871e
--- /dev/null
+++ b/nested/src/vec/vec2seq.rs
@@ -0,0 +1,115 @@
+use {
+    std::{
+        sync::Arc,
+    },
+    std::sync::RwLock,
+    crate::{
+        core::{View, Observer, ObserverExt, ObserverBroadcast, ViewPort, InnerViewPort, OuterViewPort},
+        sequence::SequenceView,
+        vec::VecDiff
+    }
+};
+
+//<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
+
+/// Adapter View implementing `Sequence` for `Vec`
+pub struct VecSequence<T>
+where T: Clone + Send + Sync + 'static {
+    cur_len: usize,
+    data: Option<Arc<RwLock<Vec<T>>>>,
+    cast: Arc<RwLock<ObserverBroadcast<dyn SequenceView<Item = T>>>>
+}
+
+
+impl<T> VecSequence<T>
+where T: Clone + Send + Sync + 'static {
+    pub fn new(
+        port: InnerViewPort<dyn SequenceView<Item = T>>
+    ) -> Arc<RwLock<Self>> {
+        let seq = Arc::new(RwLock::new(
+            VecSequence {
+                cur_len: 0,
+                data: None,
+                cast: port.get_broadcast()
+            }
+        ));
+        port.set_view(Some(seq.clone()));
+        seq
+    }
+}
+
+impl<T> Observer<RwLock<Vec<T>>> for VecSequence<T>
+where T: Clone + Send + Sync + 'static {
+    fn reset(&mut self, view: Option<Arc<RwLock<Vec<T>>>>) {
+        let old_len = self.cur_len;
+        self.data = view;
+        self.cur_len =
+            if let Some(data) = self.data.as_ref() {
+                data.read().unwrap().len()
+            } else {
+                0
+            };
+
+        self.cast.notify_each(0 .. std::cmp::max(old_len, self.cur_len));
+    }
+
+    fn notify(&mut self, diff: &VecDiff<T>) {
+        match diff {
+            VecDiff::Clear => {
+                self.cast.notify_each(0 .. self.cur_len);
+                self.cur_len = 0
+            },
+            VecDiff::Push(_) => {
+                self.cast.notify(&self.cur_len);
+                self.cur_len += 1;
+            },
+            VecDiff::Remove(idx) => {
+                self.cast.notify_each(*idx .. self.cur_len);
+                self.cur_len -= 1;
+            },
+            VecDiff::Insert{ idx, val: _ } => {
+                self.cur_len += 1;
+                self.cast.notify_each(*idx .. self.cur_len);
+            },
+            VecDiff::Update{ idx, val: _ } => {
+                self.cast.notify(&idx);
+            }
+        }
+    }
+}
+
+impl<T> View for VecSequence<T>
+where T: Clone + Send + Sync + 'static {
+    type Msg = usize;
+}
+
+impl<T> SequenceView for VecSequence<T>
+where T: Clone + Send + Sync + 'static {
+    type Item = T;
+
+    fn get(&self, idx: &usize) -> Option<T> {
+        self.data.as_ref()?
+            .read().unwrap()
+            .get(*idx).cloned()
+    }
+
+    fn len(&self) -> Option<usize> {
+        Some(self.cur_len)
+    }
+}
+
+//<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
+
+impl<T> OuterViewPort<RwLock<Vec<T>>>
+where T: Clone + Send + Sync + 'static {
+    pub fn to_sequence(&self) -> OuterViewPort<dyn SequenceView<Item = T>> {
+        let port = ViewPort::new();
+        port.add_update_hook(Arc::new(self.0.clone()));
+
+        let vec_seq = VecSequence::new(port.inner());
+        self.add_observer(vec_seq.clone());
+        port.into_outer()
+    }
+}
+
+