diff --git a/src/index/map_item.rs b/src/index/map_item.rs
new file mode 100644
index 0000000..c9bdbb0
--- /dev/null
+++ b/src/index/map_item.rs
@@ -0,0 +1,105 @@
+pub use {
+    std::{
+        sync::{Arc, RwLock},
+        ops::Range
+    },
+    crate::{
+        core::{
+            View,
+            Observer,
+            ObserverBroadcast,
+            ViewPort,
+            InnerViewPort,
+            OuterViewPort
+        },
+        index::{IndexView}
+    }
+};
+
+impl<Key: 'static, Item: 'static> OuterViewPort<dyn IndexView<Key, Item = Item>> {
+    pub fn map_item<
+        DstItem: Default + 'static,
+        F: Fn(&Item) -> DstItem + Send + Sync + 'static
+    >(
+        &self,
+        f: F
+    ) -> OuterViewPort<dyn IndexView<Key, Item = DstItem>> {
+        let port = ViewPort::new();
+        let map = MapIndexItem::new(port.inner(), f);
+        self.add_observer(map.clone());
+        port.into_outer()
+    }
+}
+
+pub struct MapIndexItem<Key, DstItem, SrcView, F>
+where SrcView: IndexView<Key> + ?Sized,
+      F: Fn(&SrcView::Item) -> DstItem + Send + Sync
+{
+    src_view: Option<Arc<SrcView>>,
+    f: F,
+    cast: Arc<RwLock<ObserverBroadcast<dyn IndexView<Key, Item = DstItem>>>>
+}
+
+impl<Key, DstItem, SrcView, F> MapIndexItem<Key, DstItem, SrcView, F>
+where Key: 'static,
+      DstItem: Default + 'static,
+      SrcView: IndexView<Key> + ?Sized + 'static,
+      F: Fn(&SrcView::Item) -> DstItem + Send + Sync + 'static
+{
+    fn new(
+        port: InnerViewPort<dyn IndexView<Key, Item = DstItem>>,
+        f: F
+    ) -> Arc<RwLock<Self>> {
+        let map = Arc::new(RwLock::new(
+            MapIndexItem {
+                src_view: None,
+                f,
+                cast: port.get_broadcast()
+            }
+        ));
+
+        port.set_view(Some(map.clone()));
+        map
+    }
+}
+
+impl<Key, DstItem, SrcView, F> View for MapIndexItem<Key, DstItem, SrcView, F>
+where SrcView: IndexView<Key> + ?Sized,
+      F: Fn(&SrcView::Item) -> DstItem + Send + Sync
+{
+    type Msg = Key;
+}
+
+impl<Key, DstItem, SrcView, F> IndexView<Key> for MapIndexItem<Key, DstItem, SrcView, F>
+where DstItem: Default,
+      SrcView: IndexView<Key> + ?Sized,
+      F: Fn(&SrcView::Item) -> DstItem + Send + Sync
+{
+    type Item = DstItem;
+
+    fn get(&self, key: &Key) -> Self::Item {
+        if let Some(v) = self.src_view.as_ref() {
+            (self.f)(&v.get(key))
+        } else {
+            DstItem::default()
+        }
+    }
+
+    fn range(&self) -> Option<Range<Key>> {
+        self.src_view.as_ref()?.range()
+    }
+}
+
+impl<Key, DstItem, SrcView, F> Observer<SrcView> for MapIndexItem<Key, DstItem, SrcView, F>
+where SrcView: IndexView<Key> + ?Sized,
+      F: Fn(&SrcView::Item) -> DstItem + Send + Sync
+{
+    fn reset(&mut self, view: Option<Arc<SrcView>>) {
+        // todo: notify on reset ??
+        self.src_view = view;
+    }
+
+    fn notify(&self, msg: &Key) {
+        self.cast.notify(msg);
+    }
+}
diff --git a/src/index/mod.rs b/src/index/mod.rs
index 7aab0c7..bd02c47 100644
--- a/src/index/mod.rs
+++ b/src/index/mod.rs
@@ -1,4 +1,6 @@
 
+pub mod map_item;
+
 use {
     std::{
         sync::{Arc, RwLock},
diff --git a/src/main.rs b/src/main.rs
index 071ee4f..6e2f903 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -2,15 +2,14 @@
 #![feature(assoc_char_funcs)]
 
 pub mod core;
-pub mod view;
+pub mod index;
+pub mod grid;
+pub mod sequence;
+pub mod singleton;
 pub mod terminal;
 
 pub mod string_editor;
 
-//pub mod singleton_buffer;
-//pub mod vec_buffer;
-//pub mod sequence_element_projection;
-
 use {
     async_std::{task},
     std::{
@@ -21,7 +20,7 @@ use {
     termion::event::{Event, Key},
     crate::{
         core::{View, Observer, ObserverExt, ViewPort},
-        view::{*},
+        index::{ImplIndexView},
         terminal::{
             TerminalView,
             TerminalAtom,
@@ -30,6 +29,7 @@ use {
             Terminal,
             TerminalCompositor
         },
+        grid::GridOffset
     }
 };
 
@@ -77,7 +77,7 @@ impl ImplIndexView for ScrambleBackground {
     type Value = Option<TerminalAtom>;
 
     fn get(&self, pos: &Point2<i16>) -> Option<TerminalAtom> {
-        if ((pos.x/2) % 2 == 0) ^ ( pos.y % 2 == 0 ) {
+        if ((pos.x/2) % 2 == 0) ^ (pos.y % 2 == 0) {
             Some(TerminalAtom::new(char::from((35+(5*pos.y+pos.x)%40) as u8), TerminalStyle::fg_color((40, 40, 40))))
         } else {
             Some(TerminalAtom::new(char::from((35+(pos.y+9*pos.x)%40) as u8), TerminalStyle::fg_color((90, 90, 90))))
@@ -96,7 +96,7 @@ async fn main() {
 
     let mut compositor = TerminalCompositor::new(term_port.inner());
     compositor.push(ViewPort::<dyn TerminalView>::with_view(Arc::new(ScrambleBackground)).into_outer());
-    
+
     let mut term = Terminal::new(term_port.outer());
     let term_writer = term.get_writer();
 
@@ -107,11 +107,37 @@ async fn main() {
         <<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
                             \*/
 
-        compositor.push(ViewPort::<dyn TerminalView>::with_view(Arc::new(Checkerboard)).into_outer());
+        let offset_port = ViewPort::<dyn TerminalView>::new();
+        let o = GridOffset::new(offset_port.inner());
+
+        let checkerboard_port = ViewPort::<dyn TerminalView>::with_view(Arc::new(Checkerboard));
+        checkerboard_port.add_observer(o.clone());
+
+        compositor.push(offset_port.into_outer());
+
         let edit_port = ViewPort::<dyn TerminalView>::new();        
         let mut editor = string_editor::StringEditor::new(edit_port.inner());
-        compositor.push(edit_port.into_outer());
 
+        let edit_offset_port = ViewPort::<dyn TerminalView>::new();
+        let edit_o = GridOffset::new(edit_offset_port.inner());
+        edit_port.add_observer(edit_o.clone());
+
+        compositor.push(
+            edit_offset_port
+                .into_outer()
+                // add a nice black background
+                .map_item(|atom| atom.map(
+                         |a| a.add_style_back(TerminalStyle::bg_color((0,0,0))))));
+
+        edit_o.write().unwrap().set_offset(Vector2::new(40, 4));
+
+        task::spawn(async move {
+            for x in 0 .. 20 {
+                async_std::task::sleep(std::time::Duration::from_millis(15)).await;
+                o.write().unwrap().set_offset(Vector2::new(x as i16, x as i16));
+            }
+        });
+        
                             /*\
         <<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
                         Event Loop