diff --git a/src/core/port.rs b/src/core/port.rs
index 5e4b428..dac9cc6 100644
--- a/src/core/port.rs
+++ b/src/core/port.rs
@@ -71,10 +71,7 @@ impl<V: View + ?Sized> Clone for ViewPort<V> {
 
 //<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
 
-#[derive(Clone)]
 pub struct InnerViewPort<V: View + ?Sized>(ViewPort<V>);
-
-#[derive(Clone)]
 pub struct OuterViewPort<V: View + ?Sized>(ViewPort<V>);
 
 //<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
@@ -98,6 +95,12 @@ impl<V: View + ?Sized> InnerViewPort<V> {
     }
 }
 
+impl<V: View + ?Sized> Clone for InnerViewPort<V> {
+    fn clone(&self) -> Self {
+        InnerViewPort(self.0.clone())
+    }
+}
+
 //<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
 
 impl<V: View + ?Sized + 'static> OuterViewPort<V> {
@@ -127,6 +130,12 @@ impl<V: View + ?Sized + 'static> OuterViewPort<V> {
     }
 }
 
+impl<V: View + ?Sized> Clone for OuterViewPort<V> {
+    fn clone(&self) -> Self {
+        OuterViewPort(self.0.clone())
+    }
+}
+
 /*
 impl<V: View + ?Sized + 'static> OuterViewPort<V>
 where V::Msg: Clone {
diff --git a/src/main.rs b/src/main.rs
index 700a3b6..0a67974 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -20,7 +20,7 @@ use {
     cgmath::{Vector2, Point2},
     termion::event::{Event, Key},
     crate::{
-        core::{View, Observer, ObserverExt, ObserverBroadcast, ViewPort},
+        core::{View, Observer, ObserverExt, ObserverBroadcast, ViewPort, OuterViewPort},
         index::{ImplIndexView},
         terminal::{
             TerminalView,
@@ -30,6 +30,7 @@ use {
             Terminal,
             TerminalCompositor
         },
+        sequence::{VecBuffer, SequenceView},
         grid::{GridOffset, GridWindowIterator},
         singleton::{SingletonView, SingletonBuffer},
         string_editor::{StringEditor, insert_view::StringInsertView},
@@ -59,71 +60,104 @@ async fn main() {
         let window_size_port = ViewPort::new();
         let mut window_size = SingletonBuffer::new(Vector2::new(0, 0), window_size_port.inner());
 
+        let opening_port = ViewPort::new();
+        let mut opening = VecBuffer::new(opening_port.inner());
+
+        let delim_port = ViewPort::new();
+        let mut delim = VecBuffer::new(delim_port.inner());
+
+        let closing_port = ViewPort::new();
+        let mut closing = VecBuffer::new(closing_port.inner());
+
+        let e1_port = ViewPort::new();
+        let mut e1 = VecBuffer::new(e1_port.inner());
+
+        let e2_port = ViewPort::new();
+        let mut e2 = VecBuffer::new(e2_port.inner());
+
+        opening.push(TerminalAtom::new('[', TerminalStyle::fg_color((180, 120, 80))));
+        delim.push(TerminalAtom::new(',', TerminalStyle::fg_color((180, 120, 80))));
+        delim.push(TerminalAtom::new(' ', TerminalStyle::fg_color((180, 120, 80))));
+        closing.push(TerminalAtom::new(']', TerminalStyle::fg_color((180, 120, 80))));
+
+        let str_list_port = ViewPort::new();
+        let mut str_list = VecBuffer::<OuterViewPort<dyn SequenceView<Item = TerminalAtom>>>::new(str_list_port.inner());
+
+        str_list.push(opening_port.outer().to_sequence());
+        str_list.push(closing_port.outer().to_sequence());
+
+        compositor.push(
+            str_list_port.outer()
+                .to_sequence()
+                .flatten()
+                .to_index()
+                .map_key(
+                    |idx| Point2::new(*idx as i16, 0 as i16),
+                    |pt| if pt.y == 0 { Some(pt.x as usize) } else { None }
+                )
+        );
+
         //<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
-        // cells
+        // welcome message
+        task::sleep(std::time::Duration::from_millis(500)).await;
+        str_list.insert(1, e1_port.outer().to_sequence());
+        for c in "Welcome!".chars() {
+            e1.push(TerminalAtom::new(c, TerminalStyle::fg_color((180, 180, 255))));
+            task::sleep(std::time::Duration::from_millis(80)).await;
+        }
+        task::sleep(std::time::Duration::from_millis(500)).await;
+        str_list.insert(2, delim_port.outer().to_sequence());
+        str_list.insert(3, e2_port.outer().to_sequence());
+        task::sleep(std::time::Duration::from_millis(80)).await;
+        for c in "This is a flattened SequenceView.".chars() {
+            e2.push(TerminalAtom::new(c, TerminalStyle::fg_color((180, 180, 255))));
+            task::sleep(std::time::Duration::from_millis(80)).await;
+        }
 
-        let cells_port = ViewPort::new();
-        let cells = cell_layout::CellLayout::with_port(cells_port.inner());
+        task::sleep(std::time::Duration::from_millis(500)).await;
 
-        compositor.push(cells_port.outer());
+        let l2_port = ViewPort::new();
+        let mut l2 = VecBuffer::new(l2_port.inner());
+
+        *str_list.get_mut(1) = l2_port.outer().to_sequence().flatten();
+
+        l2.push(opening_port.outer().to_sequence());
+
+        e1.clear();
+        l2.push(e1_port.outer().to_sequence());
+        l2.push(closing_port.outer().to_sequence());
+
+        for c in "they can even be NeStEd!".chars() {
+            e1.push(TerminalAtom::new(c, TerminalStyle::fg_color((180, 180, 255))));
+            task::sleep(std::time::Duration::from_millis(80)).await;
+        }
+
+        for i in 0 .. 10 {
+            task::sleep(std::time::Duration::from_millis(100)).await;
+
+            let col = (100+10*i, 55+20*i, 20+ 20*i);
+            *opening.get_mut(0) = TerminalAtom::new('{', TerminalStyle::fg_color(col));
+            *closing.get_mut(0) = TerminalAtom::new('}', TerminalStyle::fg_color(col));
+        }
+
+        for i in 0 .. 10 {
+            task::sleep(std::time::Duration::from_millis(100)).await;
+
+            let col = (100+10*i, 55+20*i, 20+ 20*i);
+            *opening.get_mut(0) = TerminalAtom::new('<', TerminalStyle::fg_color(col));
+            *closing.get_mut(0) = TerminalAtom::new('>', TerminalStyle::fg_color(col));
+        }
 
         //<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
         // string editor 1
         let mut editor = StringEditor::new();
         let (leveled_edit_view, leveled_edit_view_port) = LeveledTermView::new(editor.insert_view());
 
-        cell_layout::CellLayout::set_cell(
-            &cells,
-            Point2::new(0, 0),
-            leveled_edit_view_port
-                .map_item(
-                    move |_pos, atom| atom.add_style_back(
-                        TerminalStyle::fg_color((200,200,200)))));
-
         //<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
         // string editor 2
         let mut editor2 = StringEditor::new();
         let (leveled_edit2_view, leveled_edit2_view_port) = LeveledTermView::new(editor2.insert_view());
 
-        cell_layout::CellLayout::set_cell(
-            &cells,
-            Point2::new(1, 1),
-            leveled_edit2_view_port
-                .map_item(
-                    move |_pos, atom| atom.add_style_back(
-                        TerminalStyle::fg_color((200,200,200)))));
-
-        //<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
-        // another view of the string, without editor
-        cell_layout::CellLayout::set_cell(
-            &cells,
-            Point2::new(1, 0),
-            editor.get_data_port()
-                .to_sequence()
-                .to_index()
-                .map_key(
-                    |idx| Point2::new(*idx as i16, 2 + *idx as i16),
-                    |pt| if pt.x == pt.y-2 { Some(pt.x as usize) } else { None }
-                ).map_item(
-                    |_key, c| TerminalAtom::new(*c, TerminalStyle::fg_color((80, 20, 180)).add(TerminalStyle::bg_color((40,10,90))))
-                )
-        );
-
-        //<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
-        // welcome message
-
-        for c in "Welcome!".chars() {
-            editor.insert(c);
-            task::sleep(std::time::Duration::from_millis(80)).await;
-        }
-
-        task::sleep(std::time::Duration::from_millis(500)).await;
-
-        for c in "Use arrow keys to navigate.".chars() {
-            editor2.insert(c);
-            task::sleep(std::time::Duration::from_millis(80)).await;
-        }
-
         
                             /*\
         <<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
@@ -131,7 +165,7 @@ async fn main() {
         <<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
                             \*/
 
-        let mut sel = 0;
+        let mut sel = 0 as usize;
 
         leveled_edit_view.write().unwrap().set_level(if sel == 0 {1} else {0});
         leveled_edit2_view.write().unwrap().set_level(if sel == 1 {1} else {0});
diff --git a/src/sequence/flatten.rs b/src/sequence/flatten.rs
new file mode 100644
index 0000000..b2a711e
--- /dev/null
+++ b/src/sequence/flatten.rs
@@ -0,0 +1,255 @@
+use {
+    async_std::stream::StreamExt,
+    std::{
+        sync::{Arc, Weak, RwLock},
+        collections::{HashMap, HashSet}
+    },
+    crate::{
+        core::{
+            View, Observer, ObserverExt, ObserverBroadcast,
+            ViewPort, InnerViewPort, OuterViewPort,
+            channel::{ChannelSender, ChannelReceiver}
+        },
+        sequence::SequenceView
+    }
+};
+
+impl<V1, V2> OuterViewPort<V1>
+where V1: SequenceView<Item = OuterViewPort<V2>> + ?Sized + 'static,
+      V2: SequenceView + ?Sized + 'static
+{
+    pub fn flatten(&self) -> OuterViewPort<dyn SequenceView<Item = V2::Item>> {
+        let port = ViewPort::new();
+        Flatten::new(self.clone(), port.inner());
+        port.into_outer()
+    }
+}
+
+pub struct Flatten<V1, V2>
+where V1: SequenceView<Item = OuterViewPort<V2>> + ?Sized + 'static,
+      V2: SequenceView + ?Sized + 'static
+{
+    length: usize,
+    top: Arc<RwLock<TopObserver<V1, V2>>>,
+    chunks: HashMap<usize, Arc<RwLock<BotObserver<V2>>>>,
+
+    cast: Arc<RwLock<ObserverBroadcast<dyn SequenceView<Item = V2::Item>>>>
+}
+
+struct TopObserver<V1, V2>
+where V1: SequenceView<Item = OuterViewPort<V2>> + ?Sized + 'static,
+      V2: SequenceView + ?Sized + 'static
+{
+    view: Option<Arc<V1>>,
+    sender: ChannelSender<HashSet<usize>>
+}
+
+struct BotObserver<V2>
+where V2: SequenceView + ?Sized + 'static
+{
+    offset: usize,
+    view: Option<Arc<V2>>,
+    sender: ChannelSender<HashSet<usize>>
+}
+
+impl<V1, V2> Observer<V1> for TopObserver<V1, V2>
+where V1: SequenceView<Item = OuterViewPort<V2>> + ?Sized + 'static,
+      V2: SequenceView + ?Sized + 'static
+{
+    fn reset(&mut self, view: Option<Arc<V1>>) {
+        let old_len = self.view.len().unwrap_or(0);
+        self.view = view;
+        let new_len = self.view.len().unwrap_or(0);
+
+        self.notify_each(0 .. std::cmp::max(old_len, new_len));
+    }
+
+    fn notify(&self, chunk_idx: &usize) {
+        self.sender.send(*chunk_idx);
+    }
+}
+
+impl<V2> Observer<V2> for BotObserver<V2>
+where V2: SequenceView + ?Sized + 'static
+{
+    fn reset(&mut self, src: Option<Arc<V2>>) {
+        let old_len = self.view.len().unwrap_or(0);
+        self.view = src;
+        let new_len = self.view.len().unwrap_or(0);
+
+        self.notify_each(0 .. std::cmp::max(old_len, new_len));
+    }
+
+    fn notify(&self, idx: &usize) {
+        self.sender.send(*idx);
+    }
+}
+
+impl<V1, V2> View for Flatten<V1, V2>
+where V1: SequenceView<Item = OuterViewPort<V2>> + ?Sized + 'static,
+      V2: SequenceView + ?Sized + 'static
+{
+    type Msg = usize;
+}
+
+impl<V1, V2> SequenceView for Flatten<V1, V2>
+where V1: SequenceView<Item = OuterViewPort<V2>> + ?Sized + 'static,
+      V2: SequenceView + ?Sized + 'static
+{
+    type Item = V2::Item;
+
+    fn get(&self, idx: &usize) -> Option<Self::Item> {
+        let chunk = self.chunks[&self.get_chunk_idx(*idx)?].read().unwrap();
+        chunk.view.get(&(*idx - chunk.offset))
+    }
+
+    fn len(&self) -> Option<usize> {
+        Some(self.length)
+    }
+}
+
+impl<V1, V2> Flatten<V1, V2>
+where V1: SequenceView<Item = OuterViewPort<V2>> + ?Sized + 'static,
+      V2: SequenceView + ?Sized + 'static
+{
+    pub fn new(
+        top_port: OuterViewPort<V1>,
+        out_port: InnerViewPort<dyn SequenceView<Item = V2::Item>>
+    ) -> Arc<RwLock<Self>> {
+        let (sender, mut recv) = crate::core::channel::set_channel();
+
+        let top_obs = Arc::new(RwLock::new(
+            TopObserver {
+                view: None,
+                sender
+            }
+        ));
+
+        let flat = Arc::new(RwLock::new(Flatten::<V1, V2> {
+            length: 0,
+            top: top_obs.clone(),
+            chunks: HashMap::new(),
+            cast: out_port.get_broadcast()
+        }));
+
+        let f = flat.clone();
+        let cast = out_port.get_broadcast();
+        async_std::task::spawn(async move {
+            while let Some(chunk_idx) = recv.next().await {
+                if let Some(mut chunk_rcv) = f.write().unwrap().update_chunk(chunk_idx) {
+                    let f = f.clone();
+                    let cast = cast.clone();
+                    async_std::task::spawn(async move {
+                        while let Some(idx) = chunk_rcv.next().await {
+                            let mut flat = f.write().unwrap();
+
+                            let chunk = flat.chunks[&chunk_idx].read().unwrap();
+                            let chunk_offset = chunk.offset;
+                            let chunk_len = chunk.view.len().unwrap_or(0);
+                            drop(chunk);
+
+                            let mut dirty_idx = Vec::new();
+                            if idx+1 >= chunk_len {
+                                dirty_idx = flat.update_offsets(chunk_idx);
+                            }
+
+                            drop(flat);
+
+                            cast.notify(&(idx + chunk_offset));
+                            cast.notify_each(dirty_idx);
+                        }
+                    });
+                }
+            }
+        });
+
+        top_port.add_observer(top_obs);
+
+        out_port.set_view(Some(flat.clone()));
+        flat
+    }
+
+    /// the top-sequence has changed the item at chunk_idx,
+    /// create a new observer for the contained sub sequence
+    fn update_chunk(&mut self, chunk_idx: usize) -> Option<ChannelReceiver<HashSet<usize>>> {
+        if let Some(chunk_port) = self.top.read().unwrap().view.get(&chunk_idx) {
+            let (sender, recv) = crate::core::channel::set_channel();
+            let chunk_obs = Arc::new(RwLock::new(
+                BotObserver {
+                    offset:
+                    if chunk_idx > 0 {
+                        if let Some(prev_chunk) = self.chunks.get(&(chunk_idx-1)) {
+                            let prev_chunk = prev_chunk.read().unwrap();
+                            prev_chunk.offset + prev_chunk.view.len().unwrap_or(0)
+                        } else {
+                            0
+                        }
+                    } else {
+                        0
+                    },
+                    view: None,
+                    sender
+                }
+            ));
+
+            self.chunks.insert(chunk_idx, chunk_obs.clone());
+            chunk_port.add_observer(chunk_obs);
+
+            Some(recv)
+        } else {
+            self.chunks.remove(&chunk_idx);
+            None
+        }
+    }
+
+    /// recalculate all chunk offsets beginning at start_idx
+    /// and update length of flattened sequence
+    fn update_offsets(&mut self, start_idx: usize) -> Vec<usize> {
+        let top_len = self.top.read().unwrap().view.len().unwrap_or(0);
+
+        let first_chunk = self.chunks.get(&start_idx).unwrap().read().unwrap();
+        let mut start_offset = first_chunk.offset + first_chunk.view.len().unwrap_or(0);
+        let mut cur_offset = start_offset;
+
+        let mut dirty_idx = Vec::new();
+
+        for chunk_idx in start_idx+1 .. top_len {
+            if let Some(cur_chunk) = self.chunks.get(&chunk_idx) {
+                let mut cur_chunk = cur_chunk.write().unwrap();
+
+                let chunk_len = cur_chunk.view.len().unwrap_or(0);
+                let old_offset = cur_chunk.offset;
+                cur_chunk.offset = cur_offset;
+
+                if old_offset != cur_offset {
+                    dirty_idx.extend(
+                        std::cmp::min(old_offset, cur_offset)
+                            .. std::cmp::max(old_offset, cur_offset) + chunk_len
+                    );
+                }
+                cur_offset += chunk_len;
+            }
+        }
+
+        let old_length = self.length;
+        self.length = cur_offset;
+
+        dirty_idx.extend(self.length .. old_length);
+        dirty_idx
+    }
+
+    /// given an index in the flattened sequence,
+    /// which sub-sequence does it belong to?
+    fn get_chunk_idx(&self, glob_idx: usize) -> Option<usize> {
+        for chunk_idx in 0 .. self.top.read().unwrap().view.len().unwrap_or(0) {
+            if let Some(cur_chunk) = self.chunks.get(&chunk_idx) {
+                let cur_chunk = cur_chunk.read().unwrap();
+                if glob_idx < cur_chunk.offset + cur_chunk.view.len().unwrap_or(0) {
+                    return Some(chunk_idx)
+                }
+            }
+        }
+        None
+    }
+}
+
diff --git a/src/sequence/mod.rs b/src/sequence/mod.rs
index bb09a04..f10a1ea 100644
--- a/src/sequence/mod.rs
+++ b/src/sequence/mod.rs
@@ -1,6 +1,7 @@
 
 pub mod seq2idx;
 pub mod vec_buffer;
+pub mod flatten;
 
 pub use {
     seq2idx::{Sequence2Index},
diff --git a/src/sequence/vec_buffer.rs b/src/sequence/vec_buffer.rs
index b465454..23a40fe 100644
--- a/src/sequence/vec_buffer.rs
+++ b/src/sequence/vec_buffer.rs
@@ -166,6 +166,12 @@ where T: Clone + Send + Sync + 'static {
         self.cast.notify(&diff);
     }
 
+    pub fn clear(&mut self) {
+        for _ in 0 .. self.len() {
+            self.remove(0);
+        }
+    }
+
     pub fn len(&self) -> usize {
         self.data.read().unwrap().len()
     }