diff --git a/dsl/src/lib.rs b/dsl/src/lib.rs
index 703f8ba..36fc266 100644
--- a/dsl/src/lib.rs
+++ b/dsl/src/lib.rs
@@ -5,6 +5,7 @@
 extern crate const_panic;
 use const_panic::{concat_panic, PanicFmt};
 pub(crate) use ::tengri_core::*;
+use std::ops::Deref;
 pub(crate) use std::error::Error;
 pub(crate) use std::fmt::Debug;
 pub(crate) use std::sync::Arc;
@@ -61,8 +62,11 @@ pub trait DslExp: PartialEq + Clone + Default + Debug + Dsl {}
 impl<T: PartialEq + Clone + Default + Debug + Dsl> DslExp for T {}
 /// The string representation for a [Dsl] implementation.
 /// [Cst] uses `&'s str`. [Ast] uses `Arc<str>`.
-pub trait DslStr: PartialEq + Clone + Default + Debug + AsRef<str> + std::ops::Deref<Target = str> {}
-impl<T: PartialEq + Clone + Default + Debug + AsRef<str> + std::ops::Deref<Target = str>> DslStr for T {}
+pub trait DslStr: PartialEq + Clone + Default + Debug + AsRef<str> + Deref<Target = str> {
+    fn as_str (&self) -> &str     { self.as_ref() }
+    fn as_arc (&self) -> Arc<str> { self.as_ref().into() }
+}
+impl<Str: PartialEq + Clone + Default + Debug + AsRef<str> + Deref<Target = str>> DslStr for Str {}
 impl<Str: DslStr, Exp: DslExp + Dsl<Str=Str, Exp=Exp>> Val<Str, Exp> {
     pub const fn err (&self)       -> Option<DslError> {match self{Val::Error(e)=>Some(*e),        _=>None}}
     pub const fn nil (&self)       -> bool             {match self{Val::Nil=>true,                 _=>false}}
diff --git a/output/src/lib.rs b/output/src/lib.rs
index 45abdda..334c418 100644
--- a/output/src/lib.rs
+++ b/output/src/lib.rs
@@ -3,6 +3,9 @@
 #![feature(impl_trait_in_assoc_type)]
 
 pub(crate) use std::marker::PhantomData;
+pub(crate) use std::fmt::{Debug, Display};
+pub(crate) use std::ops::{Add, Sub, Mul, Div};
+pub(crate) use std::sync::{Arc, atomic::{AtomicUsize, Ordering::Relaxed}};
 pub(crate) use tengri_core::*;
 #[cfg(feature = "dsl")] pub(crate) use ::tengri_dsl::*;
 
diff --git a/output/src/ops.rs b/output/src/ops.rs
index 976ab51..6b6f401 100644
--- a/output/src/ops.rs
+++ b/output/src/ops.rs
@@ -48,32 +48,21 @@
 
 use crate::*;
 use Direction::*;
+use std::marker::PhantomData;
+use std::sync::{Arc, RwLock};
 
-mod map;   pub use self::map::*;
-mod memo;  pub use self::memo::*;
-mod stack; pub use self::stack::*;
-mod thunk; pub use self::thunk::*;
-
-/// Renders multiple things on top of each other,
-#[macro_export] macro_rules! lay {
-    ($($expr:expr),* $(,)?) => {{ let bsp = (); $(let bsp = Bsp::b(bsp, $expr);)*; bsp }}
-}
-
+/// Stack things on top of each other,
+#[macro_export] macro_rules! lay (($($expr:expr),* $(,)?) =>
+    {{ let bsp = (); $(let bsp = Bsp::b(bsp, $expr);)*; bsp }});
 /// Stack southward.
-#[macro_export] macro_rules! col {
-    ($($expr:expr),* $(,)?) => {{ let bsp = (); $(let bsp = Bsp::s(bsp, $expr);)*; bsp }};
-}
-
+#[macro_export] macro_rules! col (($($expr:expr),* $(,)?) =>
+    {{ let bsp = (); $(let bsp = Bsp::s(bsp, $expr);)*; bsp }});
 /// Stack northward.
-#[macro_export] macro_rules! col_up {
-    ($($expr:expr),* $(,)?) => {{ let bsp = (); $(let bsp = Bsp::n(bsp, $expr);)*; bsp }}
-}
-
+#[macro_export] macro_rules! col_up (($($expr:expr),* $(,)?) =>
+    {{ let bsp = (); $(let bsp = Bsp::n(bsp, $expr);)*; bsp }});
 /// Stack eastward.
-#[macro_export] macro_rules! row {
-    ($($expr:expr),* $(,)?) => {{ let bsp = (); $(let bsp = Bsp::e(bsp, $expr);)*; bsp }};
-}
-
+#[macro_export] macro_rules! row (($($expr:expr),* $(,)?) =>
+    {{ let bsp = (); $(let bsp = Bsp::e(bsp, $expr);)*; bsp }});
 /// Show an item only when a condition is true.
 pub struct When<A>(pub bool, pub A);
 impl<A> When<A> {
@@ -686,3 +675,353 @@ transform_xy_unit!("padding/x" "padding/y" "padding/xy"|self: Padding, area|{
                 //_ => None
             //})
 }
+
+/// Lazily-evaluated [Render]able.
+pub struct Thunk<E: Output, T: Render<E>, F: Fn()->T>(
+    PhantomData<E>,
+    F
+);
+impl<E: Output, T: Render<E>, F: Fn()->T> Thunk<E, T, F> {
+    pub const fn new (thunk: F) -> Self {
+        Self(PhantomData, thunk)
+    }
+}
+impl<E: Output, T: Render<E>, F: Fn()->T> Content<E> for Thunk<E, T, F> {
+    fn content (&self) -> impl Render<E> { (self.1)() }
+}
+
+pub struct ThunkBox<E: Output>(
+    PhantomData<E>,
+    Box<dyn Fn()->Box<dyn Render<E>>>,
+);
+impl<E: Output> ThunkBox<E> {
+    pub const fn new (thunk: Box<dyn Fn()->Box<dyn Render<E>>>) -> Self {
+        Self(PhantomData, thunk)
+    }
+}
+impl<E: Output> Content<E> for ThunkBox<E> {
+    fn content (&self) -> impl Render<E> { (&self.1)() }
+}
+impl<E: Output> From<Box<dyn Fn()->Box<dyn Render<E>>>> for ThunkBox<E> {
+    fn from (f: Box<dyn Fn()->Box<dyn Render<E>>>) -> Self {
+        Self(PhantomData, f)
+    }
+}
+//impl<'a, E: Output, F: Fn()->Box<dyn Render<E> + 'a> + 'a> From<F> for ThunkBox<'a, E> {
+    //fn from (f: F) -> Self {
+        //Self(Default::default(), Box::new(f))
+    //}
+//}
+
+pub struct ThunkRender<E: Output, F: Fn(&mut E)>(PhantomData<E>, F);
+impl<E: Output, F: Fn(&mut E)> ThunkRender<E, F> {
+    pub fn new (render: F) -> Self { Self(PhantomData, render) }
+}
+impl<E: Output, F: Fn(&mut E)> Content<E> for ThunkRender<E, F> {
+    fn render (&self, to: &mut E) { (self.1)(to) }
+}
+
+pub struct ThunkLayout<
+    E: Output,
+    F1: Fn(E::Area)->E::Area, 
+    F2: Fn(&mut E)
+>(
+    PhantomData<E>, 
+    F1,
+    F2
+);
+impl<E: Output, F1: Fn(E::Area)->E::Area, F2: Fn(&mut E)> ThunkLayout<E, F1, F2> {
+    pub fn new (layout: F1, render: F2) -> Self { Self(PhantomData, layout, render) }
+}
+impl<E, F1, F2> Content<E> for ThunkLayout<E, F1, F2>
+where
+    E:  Output,
+    F1: Fn(E::Area)->E::Area,
+    F2: Fn(&mut E)
+{
+    fn layout (&self, to: E::Area) -> E::Area { (self.1)(to) }
+    fn render (&self, to: &mut E) { (self.2)(to) }
+}
+
+#[derive(Debug, Default)] pub struct Memo<T, U> {
+    pub value: T,
+    pub view: Arc<RwLock<U>>
+}
+
+impl<T: PartialEq, U> Memo<T, U> {
+    pub fn new (value: T, view: U) -> Self {
+        Self { value, view: Arc::new(view.into()) }
+    }
+    pub fn update <R> (
+        &mut self,
+        newval: T,
+        render: impl Fn(&mut U, &T, &T)->R
+    ) -> Option<R> {
+        if newval != self.value {
+            let result = render(&mut*self.view.write().unwrap(), &newval, &self.value);
+            self.value = newval;
+            return Some(result);
+        }
+        None
+    }
+}
+
+/// Clear a pre-allocated buffer, then write into it.
+#[macro_export] macro_rules! rewrite {
+    ($buf:ident, $($rest:tt)*) => { |$buf,_,_|{ $buf.clear(); write!($buf, $($rest)*) } }
+}
+
+pub struct Stack<E, F> {
+    __: PhantomData<E>,
+    direction: Direction,
+    callback:  F
+}
+impl<E, F> Stack<E, F> {
+    pub fn new (direction: Direction, callback: F) -> Self {
+        Self { direction, callback, __: Default::default(), }
+    }
+    pub fn north (callback: F) -> Self {
+        Self::new(North, callback)
+    }
+    pub fn south (callback: F) -> Self {
+        Self::new(South, callback)
+    }
+    pub fn east (callback: F) -> Self {
+        Self::new(East, callback)
+    }
+    pub fn west (callback: F) -> Self {
+        Self::new(West, callback)
+    }
+}
+impl<E: Output, F: Fn(&mut dyn FnMut(&dyn Render<E>)->())->()> Content<E> for Stack<E, F> {
+    fn layout (&self, to: E::Area) -> E::Area {
+        let mut x = to.x();
+        let mut y = to.y();
+        let (mut w_used, mut w_remaining) = (E::Unit::zero(), to.w());
+        let (mut h_used, mut h_remaining) = (E::Unit::zero(), to.h());
+        (self.callback)(&mut move |component: &dyn Render<E>|{
+            let [_, _, w, h] = component.layout([x, y, w_remaining, h_remaining].into()).xywh();
+            match self.direction {
+                South => {
+                    y           = y.plus(h);
+                    h_used      = h_used.plus(h);
+                    h_remaining = h_remaining.minus(h);
+                    w_used      = w_used.max(w);
+                },
+                East  => {
+                    x           = x.plus(w);
+                    w_used      = w_used.plus(w);
+                    w_remaining = w_remaining.minus(w);
+                    h_used      = h_used.max(h);
+                },
+                North | West  => {
+                    todo!()
+                },
+                _ => unreachable!(),
+            }
+        });
+        match self.direction {
+            North | West => {
+                todo!()
+            },
+            South | East => {
+                [to.x(), to.y(), w_used.into(), h_used.into()].into()
+            },
+            _ => unreachable!(),
+        }
+    }
+    fn render (&self, to: &mut E) {
+        let mut x = to.x();
+        let mut y = to.y();
+        let (mut w_used, mut w_remaining) = (E::Unit::zero(), to.w());
+        let (mut h_used, mut h_remaining) = (E::Unit::zero(), to.h());
+        (self.callback)(&mut move |component: &dyn Render<E>|{
+            let layout = component.layout([x, y, w_remaining, h_remaining].into());
+            match self.direction {
+                South => {
+                    y           = y.plus(layout.h());
+                    h_remaining = h_remaining.minus(layout.h());
+                    h_used      = h_used.plus(layout.h());
+                    to.place(layout, component);
+                },
+                East => {
+                    x           = x.plus(layout.w());
+                    w_remaining = w_remaining.minus(layout.w());
+                    w_used      = w_used.plus(layout.h());
+                    to.place(layout, component);
+                },
+                North | West  => {
+                    todo!()
+                },
+                _ => unreachable!()
+            }
+        });
+    }
+}
+
+/*Stack::down(|add|{
+    let mut i = 0;
+    for (_, name) in self.dirs.iter() {
+        if i >= self.scroll {
+            add(&Tui::bold(i == self.index, name.as_str()))?;
+        }
+        i += 1;
+    }
+    for (_, name) in self.files.iter() {
+        if i >= self.scroll {
+            add(&Tui::bold(i == self.index, name.as_str()))?;
+        }
+        i += 1;
+    }
+    add(&format!("{}/{i}", self.index))?;
+    Ok(())
+}));*/
+
+/// Renders items from an iterator.
+pub struct Map<E, A, B, I, F, G>
+where
+    I: Iterator<Item = A> + Send + Sync,
+    F: Fn() -> I + Send + Sync,
+{
+    __: PhantomData<(E, B)>,
+    /// Function that returns iterator over stacked components
+    get_iter: F,
+    /// Function that returns each stacked component
+    get_item: G,
+}
+
+impl<'a, E, A, B, I, F, G> Map<E, A, B, I, F, G> where
+    I: Iterator<Item = A> + Send + Sync + 'a,
+    F: Fn() -> I + Send + Sync + 'a,
+{
+    pub const fn new (get_iter: F, get_item: G) -> Self {
+        Self {
+            __: PhantomData,
+            get_iter,
+            get_item
+        }
+    }
+}
+
+impl<'a, E, A, B, I, F> Map<E, A, Push<E::Unit, Align<Fixed<E::Unit, Fill<B>>>>, I, F, fn(A, usize)->B>
+where
+    E: Output,
+    B: Render<E>,
+    I: Iterator<Item = A> + Send + Sync + 'a,
+    F: Fn() -> I + Send + Sync + 'a
+{
+    pub const fn east (
+        size:     E::Unit,
+        get_iter: F,
+        get_item: impl Fn(A, usize)->B + Send + Sync
+    ) -> Map<
+        E, A,
+        Push<E::Unit, Align<Fixed<E::Unit, B>>>,
+        I, F,
+        impl Fn(A, usize)->Push<E::Unit, Align<Fixed<E::Unit, B>>> + Send + Sync
+    > {
+        Map {
+            __: PhantomData,
+            get_iter,
+            get_item: move |item: A, index: usize|{
+                // FIXME: multiply
+                let mut push: E::Unit = E::Unit::from(0u16);
+                for _ in 0..index {
+                    push = push + size;
+                }
+                Push::x(push, Align::w(Fixed::x(size, get_item(item, index))))
+            }
+        }
+    }
+
+    pub const fn south (
+        size:     E::Unit,
+        get_iter: F,
+        get_item: impl Fn(A, usize)->B + Send + Sync
+    ) -> Map<
+        E, A,
+        Push<E::Unit, Align<Fixed<E::Unit, B>>>,
+        I, F,
+        impl Fn(A, usize)->Push<E::Unit, Align<Fixed<E::Unit, B>>> + Send + Sync
+    > where
+        E: Output,
+        B: Render<E>,
+        I: Iterator<Item = A> + Send + Sync + 'a,
+        F: Fn() -> I + Send + Sync + 'a
+    {
+        Map {
+            __: PhantomData,
+            get_iter,
+            get_item: move |item: A, index: usize|{
+                // FIXME: multiply
+                let mut push: E::Unit = E::Unit::from(0u16);
+                for _ in 0..index {
+                    push = push + size;
+                }
+                Push::y(push, Align::n(Fixed::y(size, get_item(item, index))))
+            }
+        }
+    }
+}
+
+impl<'a, E, A, B, I, F, G> Content<E> for Map<E, A, B, I, F, G> where
+    E: Output,
+    B: Render<E>,
+    I: Iterator<Item = A> + Send + Sync + 'a,
+    F: Fn() -> I + Send + Sync + 'a,
+    G: Fn(A, usize)->B + Send + Sync
+{
+    fn layout (&self, area: E::Area) -> E::Area {
+        let Self { get_iter, get_item, .. } = self;
+        let mut index = 0;
+        let [mut min_x, mut min_y] = area.center();
+        let [mut max_x, mut max_y] = area.center();
+        for item in get_iter() {
+            let [x,y,w,h] = get_item(item, index).layout(area).xywh();
+            min_x = min_x.min(x.into());
+            min_y = min_y.min(y.into());
+            max_x = max_x.max((x + w).into());
+            max_y = max_y.max((y + h).into());
+            index += 1;
+        }
+        let w = max_x - min_x;
+        let h = max_y - min_y;
+        //[min_x.into(), min_y.into(), w.into(), h.into()].into()
+        area.center_xy([w.into(), h.into()].into()).into()
+    }
+    fn render (&self, to: &mut E) {
+        let Self { get_iter, get_item, .. } = self;
+        let mut index = 0;
+        let area = Content::layout(self, to.area());
+        for item in get_iter() {
+            let item = get_item(item, index);
+            //to.place(area.into(), &item);
+            to.place(item.layout(area), &item);
+            index += 1;
+        }
+    }
+}
+
+#[inline] pub fn map_south<O: Output>(
+    item_offset: O::Unit,
+    item_height: O::Unit,
+    item: impl Content<O>
+) -> impl Content<O> {
+    Push::y(item_offset, Fixed::y(item_height, Fill::x(item)))
+}
+
+#[inline] pub fn map_south_west<O: Output>(
+    item_offset: O::Unit,
+    item_height: O::Unit,
+    item: impl Content<O>
+) -> impl Content<O> {
+    Push::y(item_offset, Align::nw(Fixed::y(item_height, Fill::x(item))))
+}
+
+#[inline] pub fn map_east<O: Output>(
+    item_offset: O::Unit,
+    item_width:  O::Unit,
+    item: impl Content<O>
+) -> impl Content<O> {
+    Push::x(item_offset, Align::w(Fixed::x(item_width, Fill::y(item))))
+}
diff --git a/output/src/ops/_collect.rs b/output/src/ops/_collect.rs
deleted file mode 100644
index 5559afe..0000000
--- a/output/src/ops/_collect.rs
+++ /dev/null
@@ -1,23 +0,0 @@
-//! Groupings of elements.
-use crate::*;
-
-/// A function or closure that emits renderables.
-pub trait Collector<E: Engine>: Send + Sync + Fn(&mut dyn FnMut(&dyn Render<E>)) {}
-
-/// Any function or closure that emits renderables for the given engine matches [CollectCallback].
-impl<E, F> Collector<E> for F
-where E: Engine, F: Send + Sync + Fn(&mut dyn FnMut(&dyn Render<E>)) {}
-
-pub trait Render<E: Engine> {
-    fn area (&self, to: E::Area) -> E::Area;
-    fn render (&self, to: &mut E::Output);
-}
-
-impl<E: Engine, C: Content<E>> Render<E> for C {
-    fn area (&self, to: E::Area) -> E::Area {
-        Content::area(self, to)
-    }
-    fn render (&self, to: &mut E::Output) {
-        Content::render(self, to)
-    }
-}
diff --git a/output/src/ops/_reduce.rs b/output/src/ops/_reduce.rs
deleted file mode 100644
index dfcc00e..0000000
--- a/output/src/ops/_reduce.rs
+++ /dev/null
@@ -1,93 +0,0 @@
-use crate::*;
-
-pub struct Reduce<A, B, I, F, G>(pub PhantomData<A>, pub F, pub G) where
-    A: Send + Sync, B: Send + Sync,
-    I: Iterator<Item = B> + Send + Sync,
-    F: Fn() -> I + Send + Sync,
-    G: Fn(A, B, usize)->A + Send + Sync;
-
-impl<A, B, I, F, G> Reduce<A, B, I, F, G> where
-    A: Send + Sync, B: Send + Sync,
-    I: Iterator<Item = B> + Send + Sync,
-    F: Fn() -> I + Send + Sync,
-    G: Fn(A, B, usize)->A + Send + Sync
-{
-    pub const fn new (f: F, g: G) -> Self { Self(Default::default(), f, g) }
-}
-
-impl<E: Output, A, B, I, F, G> Content<E> for Reduce<A, B, I, F, G> where
-    A: Send + Sync, B: Send + Sync,
-    I: Iterator<Item = B> + Send + Sync,
-    F: Fn() -> I + Send + Sync,
-    G: Fn(A, B, usize)->A + Send + Sync
-{
-    fn content (&self) -> impl Render<E> {
-    }
-}
-
-/*
-
-    //pub fn reduce <E, T, I, R, F>(iterator: I, callback: F) -> Reduce<E, T, I, R, F> where
-        //E: Output,
-        //I: Iterator<Item = T> + Send + Sync,
-        //R: Render<E>,
-        //F: Fn(R, T, usize) -> R + Send + Sync
-    //{
-        //Reduce(Default::default(), iterator, callback)
-    //}
-pub struct Reduce<E, T, I, R, F>(PhantomData<(E, R)>, I, F) where
-    E: Output,
-    I: Iterator<Item = T> + Send + Sync,
-    R: Render<E>,
-    F: Fn(R, T, usize) -> R + Send + Sync;
-impl<E, T, I, R, F> Content<E> for Reduce<E, T, I, R, F> where
-    E: Output,
-    I: Iterator<Item = T> + Send + Sync,
-    R: Render<E>,
-    F: Fn(R, T, usize) -> R + Send + Sync
-{
-    fn render (&self, to: &mut E) {
-        todo!()
-    }
-}
-*/
-
-//macro_rules! define_ops {
-    //($Trait:ident<$E:ident:$Output:path> { $(
-        //$(#[$attr:meta $($attr_args:tt)*])*
-        //(
-            //$fn:ident
-            //$(<$($G:ident$(:$Gen:path)?, )+>)?
-            //$Op:ident
-            //($($arg:ident:$Arg:ty),*)
-        //)
-    //)* }) => {
-        //impl<$E: $Output> $Trait<E> for E {}
-        //pub trait $Trait<$E: $Output> {
-            //$(
-                //$(#[$attr $($attr_args)*])*
-                //fn $fn $(<$($G),+>)?
-                //($($arg:$Arg),*)-> $Op<$($(, $G)+)?> 
-                //$(where $($G: $($Gen + Send + Sync)?),+)?
-                //{ $Op($($arg),*) }
-            //)*
-        //}
-    //}
-//}
-
-//define_ops! {
-    //Layout<E: Output> {
-        //(when <A: Render<E>,>
-            //When(cond: bool, item: A))
-        ///// When `cond` is `true`, render `a`, otherwise render `b`.
-        //(either <A: Render<E>, B: Render<E>,>
-            //Either(cond: bool, a: A, b: B))
-        ///// If `opt` is `Some(T)` renders `cb(t)`, otherwise nothing.
-        //(opt <A, F: Fn(A) -> B, B: Render<E>,>
-            //Opt(option: Option<A>, cb: F))
-        ///// Maps items of iterator through callback.
-        //(map <A, B: Render<E>, I: Iterator<Item = A>, F: Fn() -> I, G: Fn(A, usize)->B,>
-            //Map(get_iterator: F, callback: G))
-    //}
-//}
-
diff --git a/output/src/ops/map.rs b/output/src/ops/map.rs
deleted file mode 100644
index d124569..0000000
--- a/output/src/ops/map.rs
+++ /dev/null
@@ -1,150 +0,0 @@
-use crate::*;
-
-/// Renders items from an iterator.
-pub struct Map<E, A, B, I, F, G>
-where
-    I: Iterator<Item = A> + Send + Sync,
-    F: Fn() -> I + Send + Sync,
-{
-    __: PhantomData<(E, B)>,
-    /// Function that returns iterator over stacked components
-    get_iter: F,
-    /// Function that returns each stacked component
-    get_item: G,
-}
-
-impl<'a, E, A, B, I, F, G> Map<E, A, B, I, F, G> where
-    I: Iterator<Item = A> + Send + Sync + 'a,
-    F: Fn() -> I + Send + Sync + 'a,
-{
-    pub const fn new (get_iter: F, get_item: G) -> Self {
-        Self {
-            __: PhantomData,
-            get_iter,
-            get_item
-        }
-    }
-}
-
-impl<'a, E, A, B, I, F> Map<E, A, Push<E::Unit, Align<Fixed<E::Unit, Fill<B>>>>, I, F, fn(A, usize)->B>
-where
-    E: Output,
-    B: Render<E>,
-    I: Iterator<Item = A> + Send + Sync + 'a,
-    F: Fn() -> I + Send + Sync + 'a
-{
-    pub const fn east (
-        size:     E::Unit,
-        get_iter: F,
-        get_item: impl Fn(A, usize)->B + Send + Sync
-    ) -> Map<
-        E, A,
-        Push<E::Unit, Align<Fixed<E::Unit, B>>>,
-        I, F,
-        impl Fn(A, usize)->Push<E::Unit, Align<Fixed<E::Unit, B>>> + Send + Sync
-    > {
-        Map {
-            __: PhantomData,
-            get_iter,
-            get_item: move |item: A, index: usize|{
-                // FIXME: multiply
-                let mut push: E::Unit = E::Unit::from(0u16);
-                for _ in 0..index {
-                    push = push + size;
-                }
-                Push::x(push, Align::w(Fixed::x(size, get_item(item, index))))
-            }
-        }
-    }
-
-    pub const fn south (
-        size:     E::Unit,
-        get_iter: F,
-        get_item: impl Fn(A, usize)->B + Send + Sync
-    ) -> Map<
-        E, A,
-        Push<E::Unit, Align<Fixed<E::Unit, B>>>,
-        I, F,
-        impl Fn(A, usize)->Push<E::Unit, Align<Fixed<E::Unit, B>>> + Send + Sync
-    > where
-        E: Output,
-        B: Render<E>,
-        I: Iterator<Item = A> + Send + Sync + 'a,
-        F: Fn() -> I + Send + Sync + 'a
-    {
-        Map {
-            __: PhantomData,
-            get_iter,
-            get_item: move |item: A, index: usize|{
-                // FIXME: multiply
-                let mut push: E::Unit = E::Unit::from(0u16);
-                for _ in 0..index {
-                    push = push + size;
-                }
-                Push::y(push, Align::n(Fixed::y(size, get_item(item, index))))
-            }
-        }
-    }
-}
-
-impl<'a, E, A, B, I, F, G> Content<E> for Map<E, A, B, I, F, G> where
-    E: Output,
-    B: Render<E>,
-    I: Iterator<Item = A> + Send + Sync + 'a,
-    F: Fn() -> I + Send + Sync + 'a,
-    G: Fn(A, usize)->B + Send + Sync
-{
-    fn layout (&self, area: E::Area) -> E::Area {
-        let Self { get_iter, get_item, .. } = self;
-        let mut index = 0;
-        let [mut min_x, mut min_y] = area.center();
-        let [mut max_x, mut max_y] = area.center();
-        for item in get_iter() {
-            let [x,y,w,h] = get_item(item, index).layout(area).xywh();
-            min_x = min_x.min(x.into());
-            min_y = min_y.min(y.into());
-            max_x = max_x.max((x + w).into());
-            max_y = max_y.max((y + h).into());
-            index += 1;
-        }
-        let w = max_x - min_x;
-        let h = max_y - min_y;
-        //[min_x.into(), min_y.into(), w.into(), h.into()].into()
-        area.center_xy([w.into(), h.into()].into()).into()
-    }
-    fn render (&self, to: &mut E) {
-        let Self { get_iter, get_item, .. } = self;
-        let mut index = 0;
-        let area = Content::layout(self, to.area());
-        for item in get_iter() {
-            let item = get_item(item, index);
-            //to.place(area.into(), &item);
-            to.place(item.layout(area), &item);
-            index += 1;
-        }
-    }
-}
-
-#[inline] pub fn map_south<O: Output>(
-    item_offset: O::Unit,
-    item_height: O::Unit,
-    item: impl Content<O>
-) -> impl Content<O> {
-    Push::y(item_offset, Fixed::y(item_height, Fill::x(item)))
-}
-
-#[inline] pub fn map_south_west<O: Output>(
-    item_offset: O::Unit,
-    item_height: O::Unit,
-    item: impl Content<O>
-) -> impl Content<O> {
-    Push::y(item_offset, Align::nw(Fixed::y(item_height, Fill::x(item))))
-}
-
-#[inline] pub fn map_east<O: Output>(
-    item_offset: O::Unit,
-    item_width:  O::Unit,
-    item: impl Content<O>
-) -> impl Content<O> {
-    Push::x(item_offset, Align::w(Fixed::x(item_width, Fill::y(item))))
-}
diff --git a/output/src/ops/memo.rs b/output/src/ops/memo.rs
deleted file mode 100644
index 8168f2d..0000000
--- a/output/src/ops/memo.rs
+++ /dev/null
@@ -1,30 +0,0 @@
-//use crate::*;
-use std::sync::{Arc, RwLock};
-
-#[derive(Debug, Default)] pub struct Memo<T, U> {
-    pub value: T,
-    pub view: Arc<RwLock<U>>
-}
-
-impl<T: PartialEq, U> Memo<T, U> {
-    pub fn new (value: T, view: U) -> Self {
-        Self { value, view: Arc::new(view.into()) }
-    }
-    pub fn update <R> (
-        &mut self,
-        newval: T,
-        render: impl Fn(&mut U, &T, &T)->R
-    ) -> Option<R> {
-        if newval != self.value {
-            let result = render(&mut*self.view.write().unwrap(), &newval, &self.value);
-            self.value = newval;
-            return Some(result);
-        }
-        None
-    }
-}
-
-/// Clear a pre-allocated buffer, then write into it.
-#[macro_export] macro_rules! rewrite {
-    ($buf:ident, $($rest:tt)*) => { |$buf,_,_|{ $buf.clear(); write!($buf, $($rest)*) } }
-}
diff --git a/output/src/ops/stack.rs b/output/src/ops/stack.rs
deleted file mode 100644
index 59930ce..0000000
--- a/output/src/ops/stack.rs
+++ /dev/null
@@ -1,109 +0,0 @@
-use crate::*;
-use Direction::*;
-
-pub struct Stack<E, F> {
-    __: PhantomData<E>,
-    direction: Direction,
-    callback:  F
-}
-impl<E, F> Stack<E, F> {
-    pub fn new (direction: Direction, callback: F) -> Self {
-        Self { direction, callback, __: Default::default(), }
-    }
-    pub fn north (callback: F) -> Self {
-        Self::new(North, callback)
-    }
-    pub fn south (callback: F) -> Self {
-        Self::new(South, callback)
-    }
-    pub fn east (callback: F) -> Self {
-        Self::new(East, callback)
-    }
-    pub fn west (callback: F) -> Self {
-        Self::new(West, callback)
-    }
-}
-impl<E: Output, F: Fn(&mut dyn FnMut(&dyn Render<E>)->())->()> Content<E> for Stack<E, F> {
-    fn layout (&self, to: E::Area) -> E::Area {
-        let mut x = to.x();
-        let mut y = to.y();
-        let (mut w_used, mut w_remaining) = (E::Unit::zero(), to.w());
-        let (mut h_used, mut h_remaining) = (E::Unit::zero(), to.h());
-        (self.callback)(&mut move |component: &dyn Render<E>|{
-            let [_, _, w, h] = component.layout([x, y, w_remaining, h_remaining].into()).xywh();
-            match self.direction {
-                South => {
-                    y           = y.plus(h);
-                    h_used      = h_used.plus(h);
-                    h_remaining = h_remaining.minus(h);
-                    w_used      = w_used.max(w);
-                },
-                East  => {
-                    x           = x.plus(w);
-                    w_used      = w_used.plus(w);
-                    w_remaining = w_remaining.minus(w);
-                    h_used      = h_used.max(h);
-                },
-                North | West  => {
-                    todo!()
-                },
-                _ => unreachable!(),
-            }
-        });
-        match self.direction {
-            North | West => {
-                todo!()
-            },
-            South | East => {
-                [to.x(), to.y(), w_used.into(), h_used.into()].into()
-            },
-            _ => unreachable!(),
-        }
-    }
-    fn render (&self, to: &mut E) {
-        let mut x = to.x();
-        let mut y = to.y();
-        let (mut w_used, mut w_remaining) = (E::Unit::zero(), to.w());
-        let (mut h_used, mut h_remaining) = (E::Unit::zero(), to.h());
-        (self.callback)(&mut move |component: &dyn Render<E>|{
-            let layout = component.layout([x, y, w_remaining, h_remaining].into());
-            match self.direction {
-                South => {
-                    y           = y.plus(layout.h());
-                    h_remaining = h_remaining.minus(layout.h());
-                    h_used      = h_used.plus(layout.h());
-                    to.place(layout, component);
-                },
-                East => {
-                    x           = x.plus(layout.w());
-                    w_remaining = w_remaining.minus(layout.w());
-                    w_used      = w_used.plus(layout.h());
-                    to.place(layout, component);
-                },
-                North | West  => {
-                    todo!()
-                },
-                _ => unreachable!()
-            }
-        });
-    }
-}
-
-/*Stack::down(|add|{
-    let mut i = 0;
-    for (_, name) in self.dirs.iter() {
-        if i >= self.scroll {
-            add(&Tui::bold(i == self.index, name.as_str()))?;
-        }
-        i += 1;
-    }
-    for (_, name) in self.files.iter() {
-        if i >= self.scroll {
-            add(&Tui::bold(i == self.index, name.as_str()))?;
-        }
-        i += 1;
-    }
-    add(&format!("{}/{i}", self.index))?;
-    Ok(())
-}));*/
-
diff --git a/output/src/ops/thunk.rs b/output/src/ops/thunk.rs
deleted file mode 100644
index d0e2877..0000000
--- a/output/src/ops/thunk.rs
+++ /dev/null
@@ -1,69 +0,0 @@
-use crate::*;
-use std::marker::PhantomData;
-
-/// Lazily-evaluated [Render]able.
-pub struct Thunk<E: Output, T: Render<E>, F: Fn()->T>(
-    PhantomData<E>,
-    F
-);
-impl<E: Output, T: Render<E>, F: Fn()->T> Thunk<E, T, F> {
-    pub const fn new (thunk: F) -> Self {
-        Self(PhantomData, thunk)
-    }
-}
-impl<E: Output, T: Render<E>, F: Fn()->T> Content<E> for Thunk<E, T, F> {
-    fn content (&self) -> impl Render<E> { (self.1)() }
-}
-
-pub struct ThunkBox<E: Output>(
-    PhantomData<E>,
-    Box<dyn Fn()->Box<dyn Render<E>>>,
-);
-impl<E: Output> ThunkBox<E> {
-    pub const fn new (thunk: Box<dyn Fn()->Box<dyn Render<E>>>) -> Self {
-        Self(PhantomData, thunk)
-    }
-}
-impl<E: Output> Content<E> for ThunkBox<E> {
-    fn content (&self) -> impl Render<E> { (&self.1)() }
-}
-impl<E: Output> From<Box<dyn Fn()->Box<dyn Render<E>>>> for ThunkBox<E> {
-    fn from (f: Box<dyn Fn()->Box<dyn Render<E>>>) -> Self {
-        Self(PhantomData, f)
-    }
-}
-//impl<'a, E: Output, F: Fn()->Box<dyn Render<E> + 'a> + 'a> From<F> for ThunkBox<'a, E> {
-    //fn from (f: F) -> Self {
-        //Self(Default::default(), Box::new(f))
-    //}
-//}
-
-pub struct ThunkRender<E: Output, F: Fn(&mut E)>(PhantomData<E>, F);
-impl<E: Output, F: Fn(&mut E)> ThunkRender<E, F> {
-    pub fn new (render: F) -> Self { Self(PhantomData, render) }
-}
-impl<E: Output, F: Fn(&mut E)> Content<E> for ThunkRender<E, F> {
-    fn render (&self, to: &mut E) { (self.1)(to) }
-}
-
-pub struct ThunkLayout<
-    E: Output,
-    F1: Fn(E::Area)->E::Area, 
-    F2: Fn(&mut E)
->(
-    PhantomData<E>, 
-    F1,
-    F2
-);
-impl<E: Output, F1: Fn(E::Area)->E::Area, F2: Fn(&mut E)> ThunkLayout<E, F1, F2> {
-    pub fn new (layout: F1, render: F2) -> Self { Self(PhantomData, layout, render) }
-}
-impl<E, F1, F2> Content<E> for ThunkLayout<E, F1, F2>
-where
-    E:  Output,
-    F1: Fn(E::Area)->E::Area,
-    F2: Fn(&mut E)
-{
-    fn layout (&self, to: E::Area) -> E::Area { (self.1)(to) }
-    fn render (&self, to: &mut E) { (self.2)(to) }
-}
diff --git a/output/src/space.rs b/output/src/space.rs
index 056e12f..3e1298b 100644
--- a/output/src/space.rs
+++ b/output/src/space.rs
@@ -1,5 +1,274 @@
-mod area;       pub use self::area::*;
-mod coordinate; pub use self::coordinate::*;
-mod direction;  pub use self::direction::*;
-mod measure;    pub use self::measure::*;
-mod size;       pub use self::size::*;
+use crate::*;
+use Direction::*;
+
+/// A cardinal direction.
+#[derive(Copy, Clone, PartialEq, Debug)]
+#[cfg_attr(test, derive(Arbitrary))]
+pub enum Direction {
+    North, South, East, West, Above, Below
+}
+
+impl Direction {
+    pub fn split_fixed <N: Coordinate> (self, area: impl Area<N>, a: N) -> ([N;4],[N;4]) {
+        let [x, y, w, h] = area.xywh();
+        match self {
+            North => ([x, y.plus(h).minus(a), w, a], [x, y, w, h.minus(a)]),
+            South => ([x, y, w, a], [x, y.plus(a), w, h.minus(a)]),
+            East  => ([x, y, a, h], [x.plus(a), y, w.minus(a), h]),
+            West  => ([x.plus(w).minus(a), y, a, h], [x, y, w.minus(a), h]),
+            Above | Below => (area.xywh(), area.xywh())
+        }
+    }
+}
+
+/// A linear coordinate.
+pub trait Coordinate: Send + Sync + Copy
+    + Add<Self, Output=Self>
+    + Sub<Self, Output=Self>
+    + Mul<Self, Output=Self>
+    + Div<Self, Output=Self>
+    + Ord + PartialEq + Eq
+    + Debug + Display + Default
+    + From<u16> + Into<u16>
+    + Into<usize>
+    + Into<f64>
+{
+    fn zero () -> Self { 0.into() }
+    fn plus (self, other: Self) -> Self;
+    fn minus (self, other: Self) -> Self {
+        if self >= other {
+            self - other
+        } else {
+            0.into()
+        }
+    }
+}
+
+impl Coordinate for u16 {
+    fn plus (self, other: Self) -> Self {
+        self.saturating_add(other)
+    }
+}
+
+pub trait Area<N: Coordinate>: From<[N;4]> + Debug + Copy {
+    fn x (&self) -> N;
+    fn y (&self) -> N;
+    fn w (&self) -> N;
+    fn h (&self) -> N;
+    fn zero () -> [N;4] {
+        [N::zero(), N::zero(), N::zero(), N::zero()]
+    }
+    fn from_position (pos: impl Size<N>) -> [N;4] {
+        let [x, y] = pos.wh();
+        [x, y, 0.into(), 0.into()]
+    }
+    fn from_size (size: impl Size<N>) -> [N;4] {
+        let [w, h] = size.wh();
+        [0.into(), 0.into(), w, h]
+    }
+    fn expect_min (&self, w: N, h: N) -> Usually<&Self> {
+        if self.w() < w || self.h() < h {
+            Err(format!("min {w}x{h}").into())
+        } else {
+            Ok(self)
+        }
+    }
+    fn xy (&self) -> [N;2] {
+        [self.x(), self.y()]
+    }
+    fn wh (&self) -> [N;2] {
+        [self.w(), self.h()]
+    }
+    fn xywh (&self) -> [N;4] {
+        [self.x(), self.y(), self.w(), self.h()]
+    }
+    fn clip_h (&self, h: N) -> [N;4] {
+        [self.x(), self.y(), self.w(), self.h().min(h)]
+    }
+    fn clip_w (&self, w: N) -> [N;4] {
+        [self.x(), self.y(), self.w().min(w), self.h()]
+    }
+    fn clip (&self, wh: impl Size<N>) -> [N;4] {
+        [self.x(), self.y(), wh.w(), wh.h()]
+    }
+    fn set_w (&self, w: N) -> [N;4] {
+        [self.x(), self.y(), w, self.h()]
+    }
+    fn set_h (&self, h: N) -> [N;4] {
+        [self.x(), self.y(), self.w(), h]
+    }
+    fn x2 (&self) -> N {
+        self.x().plus(self.w())
+    }
+    fn y2 (&self) -> N {
+        self.y().plus(self.h())
+    }
+    fn lrtb (&self) -> [N;4] {
+        [self.x(), self.x2(), self.y(), self.y2()]
+    }
+    fn center (&self) -> [N;2] {
+        [self.x().plus(self.w()/2.into()), self.y().plus(self.h()/2.into())]
+    }
+    fn center_x (&self, n: N) -> [N;4] {
+        let [x, y, w, h] = self.xywh();
+        [(x.plus(w / 2.into())).minus(n / 2.into()), y.plus(h / 2.into()), n, 1.into()]
+    }
+    fn center_y (&self, n: N) -> [N;4] {
+        let [x, y, w, h] = self.xywh();
+        [x.plus(w / 2.into()), (y.plus(h / 2.into())).minus(n / 2.into()), 1.into(), n]
+    }
+    fn center_xy (&self, [n, m]: [N;2]) -> [N;4] {
+        let [x, y, w, h] = self.xywh();
+        [(x.plus(w / 2.into())).minus(n / 2.into()), (y.plus(h / 2.into())).minus(m / 2.into()), n, m]
+    }
+    fn centered (&self) -> [N;2] {
+        [self.x().minus(self.w()/2.into()), self.y().minus(self.h()/2.into())]
+    }
+    fn iter_x (&self) -> impl Iterator<Item = N> where N: std::iter::Step {
+        self.x()..(self.x()+self.w())
+    }
+    fn iter_y (&self) -> impl Iterator<Item = N> where N: std::iter::Step {
+        self.y()..(self.y()+self.h())
+    }
+}
+
+impl<N: Coordinate> Area<N> for (N, N, N, N) {
+    fn x (&self) -> N { self.0 }
+    fn y (&self) -> N { self.1 }
+    fn w (&self) -> N { self.2 }
+    fn h (&self) -> N { self.3 }
+}
+
+impl<N: Coordinate> Area<N> for [N;4] {
+    fn x (&self) -> N { self[0] }
+    fn y (&self) -> N { self[1] }
+    fn w (&self) -> N { self[2] }
+    fn h (&self) -> N { self[3] }
+}
+
+pub trait Size<N: Coordinate>: From<[N;2]> + Debug + Copy {
+    fn x (&self) -> N;
+    fn y (&self) -> N;
+    fn w (&self) -> N { self.x() }
+    fn h (&self) -> N { self.y() }
+    fn wh (&self) -> [N;2] { [self.x(), self.y()] }
+    fn clip_w (&self, w: N) -> [N;2] { [self.w().min(w), self.h()] }
+    fn clip_h (&self, h: N) -> [N;2] { [self.w(), self.h().min(h)] }
+    fn expect_min (&self, w: N, h: N) -> Usually<&Self> {
+        if self.w() < w || self.h() < h {
+            Err(format!("min {w}x{h}").into())
+        } else {
+            Ok(self)
+        }
+    }
+    fn zero () -> [N;2] {
+        [N::zero(), N::zero()]
+    }
+    fn to_area_pos (&self) -> [N;4] {
+        let [x, y] = self.wh();
+        [x, y, 0.into(), 0.into()]
+    }
+    fn to_area_size (&self) -> [N;4] {
+        let [w, h] = self.wh();
+        [0.into(), 0.into(), w, h]
+    }
+}
+
+impl<N: Coordinate> Size<N> for (N, N) {
+    fn x (&self) -> N { self.0 }
+    fn y (&self) -> N { self.1 }
+}
+
+impl<N: Coordinate> Size<N> for [N;2] {
+    fn x (&self) -> N { self[0] }
+    fn y (&self) -> N { self[1] }
+}
+
+pub trait HasSize<E: Output> {
+    fn size (&self) -> &Measure<E>;
+    fn width (&self) -> usize {
+        self.size().w()
+    }
+    fn height (&self) -> usize {
+        self.size().h()
+    }
+}
+
+impl<E: Output, T: Has<Measure<E>>> HasSize<E> for T {
+    fn size (&self) -> &Measure<E> {
+        self.get()
+    }
+}
+
+/// A widget that tracks its render width and height
+#[derive(Default)]
+pub struct Measure<E: Output> {
+    _engine: PhantomData<E>,
+    pub x: Arc<AtomicUsize>,
+    pub y: Arc<AtomicUsize>,
+}
+
+// TODO: 🡘  🡙 ←🡙→ indicator to expand window when too small
+impl<E: Output> Content<E> for Measure<E> {
+    fn render (&self, to: &mut E) {
+        self.x.store(to.area().w().into(), Relaxed);
+        self.y.store(to.area().h().into(), Relaxed);
+    }
+}
+
+impl<E: Output> Clone for Measure<E> {
+    fn clone (&self) -> Self {
+        Self {
+            _engine: Default::default(),
+            x: self.x.clone(),
+            y: self.y.clone(),
+        }
+    }
+}
+
+impl<E: Output> std::fmt::Debug for Measure<E> {
+    fn fmt (&self, f: &mut std::fmt::Formatter<'_>) -> std::result::Result<(), std::fmt::Error> {
+        f.debug_struct("Measure")
+            .field("width",  &self.x)
+            .field("height", &self.y)
+            .finish()
+    }
+}
+
+impl<E: Output> Measure<E> {
+    pub fn new () -> Self {
+        Self {
+            _engine: PhantomData::default(),
+            x: Arc::new(0.into()),
+            y: Arc::new(0.into()),
+        }
+    }
+    pub fn set_w (&self, w: impl Into<usize>) -> &Self {
+        self.x.store(w.into(), Relaxed);
+        self
+    }
+    pub fn set_h (&self, h: impl Into<usize>) -> &Self {
+        self.y.store(h.into(), Relaxed);
+        self
+    }
+    pub fn set_wh (&self, w: impl Into<usize>, h: impl Into<usize>) -> &Self {
+        self.set_w(w);
+        self.set_h(h);
+        self
+    }
+    pub fn w (&self) -> usize {
+        self.x.load(Relaxed)
+    }
+    pub fn h (&self) -> usize {
+        self.y.load(Relaxed)
+    }
+    pub fn wh (&self) -> [usize;2] {
+        [self.w(), self.h()]
+    }
+    pub fn format (&self) -> Arc<str> {
+        format!("{}x{}", self.w(), self.h()).into()
+    }
+    pub fn of <T: Render<E>> (&self, item: T) -> Bsp<Fill<&Self>, T> {
+        Bsp::b(Fill::xy(self), item)
+    }
+}
diff --git a/output/src/space/area.rs b/output/src/space/area.rs
deleted file mode 100644
index 4393790..0000000
--- a/output/src/space/area.rs
+++ /dev/null
@@ -1,98 +0,0 @@
-use crate::*;
-use std::fmt::Debug;
-
-pub trait Area<N: Coordinate>: From<[N;4]> + Debug + Copy {
-    fn x (&self) -> N;
-    fn y (&self) -> N;
-    fn w (&self) -> N;
-    fn h (&self) -> N;
-    fn zero () -> [N;4] {
-        [N::zero(), N::zero(), N::zero(), N::zero()]
-    }
-    fn from_position (pos: impl Size<N>) -> [N;4] {
-        let [x, y] = pos.wh();
-        [x, y, 0.into(), 0.into()]
-    }
-    fn from_size (size: impl Size<N>) -> [N;4] {
-        let [w, h] = size.wh();
-        [0.into(), 0.into(), w, h]
-    }
-    fn expect_min (&self, w: N, h: N) -> Usually<&Self> {
-        if self.w() < w || self.h() < h {
-            Err(format!("min {w}x{h}").into())
-        } else {
-            Ok(self)
-        }
-    }
-    fn xy (&self) -> [N;2] {
-        [self.x(), self.y()]
-    }
-    fn wh (&self) -> [N;2] {
-        [self.w(), self.h()]
-    }
-    fn xywh (&self) -> [N;4] {
-        [self.x(), self.y(), self.w(), self.h()]
-    }
-    fn clip_h (&self, h: N) -> [N;4] {
-        [self.x(), self.y(), self.w(), self.h().min(h)]
-    }
-    fn clip_w (&self, w: N) -> [N;4] {
-        [self.x(), self.y(), self.w().min(w), self.h()]
-    }
-    fn clip (&self, wh: impl Size<N>) -> [N;4] {
-        [self.x(), self.y(), wh.w(), wh.h()]
-    }
-    fn set_w (&self, w: N) -> [N;4] {
-        [self.x(), self.y(), w, self.h()]
-    }
-    fn set_h (&self, h: N) -> [N;4] {
-        [self.x(), self.y(), self.w(), h]
-    }
-    fn x2 (&self) -> N {
-        self.x().plus(self.w())
-    }
-    fn y2 (&self) -> N {
-        self.y().plus(self.h())
-    }
-    fn lrtb (&self) -> [N;4] {
-        [self.x(), self.x2(), self.y(), self.y2()]
-    }
-    fn center (&self) -> [N;2] {
-        [self.x().plus(self.w()/2.into()), self.y().plus(self.h()/2.into())]
-    }
-    fn center_x (&self, n: N) -> [N;4] {
-        let [x, y, w, h] = self.xywh();
-        [(x.plus(w / 2.into())).minus(n / 2.into()), y.plus(h / 2.into()), n, 1.into()]
-    }
-    fn center_y (&self, n: N) -> [N;4] {
-        let [x, y, w, h] = self.xywh();
-        [x.plus(w / 2.into()), (y.plus(h / 2.into())).minus(n / 2.into()), 1.into(), n]
-    }
-    fn center_xy (&self, [n, m]: [N;2]) -> [N;4] {
-        let [x, y, w, h] = self.xywh();
-        [(x.plus(w / 2.into())).minus(n / 2.into()), (y.plus(h / 2.into())).minus(m / 2.into()), n, m]
-    }
-    fn centered (&self) -> [N;2] {
-        [self.x().minus(self.w()/2.into()), self.y().minus(self.h()/2.into())]
-    }
-    fn iter_x (&self) -> impl Iterator<Item = N> where N: std::iter::Step {
-        self.x()..(self.x()+self.w())
-    }
-    fn iter_y (&self) -> impl Iterator<Item = N> where N: std::iter::Step {
-        self.y()..(self.y()+self.h())
-    }
-}
-
-impl<N: Coordinate> Area<N> for (N, N, N, N) {
-    fn x (&self) -> N { self.0 }
-    fn y (&self) -> N { self.1 }
-    fn w (&self) -> N { self.2 }
-    fn h (&self) -> N { self.3 }
-}
-
-impl<N: Coordinate> Area<N> for [N;4] {
-    fn x (&self) -> N { self[0] }
-    fn y (&self) -> N { self[1] }
-    fn w (&self) -> N { self[2] }
-    fn h (&self) -> N { self[3] }
-}
diff --git a/output/src/space/coordinate.rs b/output/src/space/coordinate.rs
deleted file mode 100644
index 262be9e..0000000
--- a/output/src/space/coordinate.rs
+++ /dev/null
@@ -1,31 +0,0 @@
-use std::fmt::{Debug, Display};
-use std::ops::{Add, Sub, Mul, Div};
-
-/// A linear coordinate.
-pub trait Coordinate: Send + Sync + Copy
-    + Add<Self, Output=Self>
-    + Sub<Self, Output=Self>
-    + Mul<Self, Output=Self>
-    + Div<Self, Output=Self>
-    + Ord + PartialEq + Eq
-    + Debug + Display + Default
-    + From<u16> + Into<u16>
-    + Into<usize>
-    + Into<f64>
-{
-    fn zero () -> Self { 0.into() }
-    fn plus (self, other: Self) -> Self;
-    fn minus (self, other: Self) -> Self {
-        if self >= other {
-            self - other
-        } else {
-            0.into()
-        }
-    }
-}
-
-impl Coordinate for u16 {
-    fn plus (self, other: Self) -> Self {
-        self.saturating_add(other)
-    }
-}
diff --git a/output/src/space/direction.rs b/output/src/space/direction.rs
deleted file mode 100644
index ed9df46..0000000
--- a/output/src/space/direction.rs
+++ /dev/null
@@ -1,22 +0,0 @@
-use crate::*;
-use crate::Direction::*;
-
-/// A cardinal direction.
-#[derive(Copy, Clone, PartialEq, Debug)]
-#[cfg_attr(test, derive(Arbitrary))]
-pub enum Direction {
-    North, South, East, West, Above, Below
-}
-
-impl Direction {
-    pub fn split_fixed <N: Coordinate> (self, area: impl Area<N>, a: N) -> ([N;4],[N;4]) {
-        let [x, y, w, h] = area.xywh();
-        match self {
-            North => ([x, y.plus(h).minus(a), w, a], [x, y, w, h.minus(a)]),
-            South => ([x, y, w, a], [x, y.plus(a), w, h.minus(a)]),
-            East  => ([x, y, a, h], [x.plus(a), y, w.minus(a), h]),
-            West  => ([x.plus(w).minus(a), y, a, h], [x, y, w.minus(a), h]),
-            Above | Below => (area.xywh(), area.xywh())
-        }
-    }
-}
diff --git a/output/src/space/measure.rs b/output/src/space/measure.rs
deleted file mode 100644
index 9ed5c2c..0000000
--- a/output/src/space/measure.rs
+++ /dev/null
@@ -1,91 +0,0 @@
-use crate::*;
-use std::sync::{Arc, atomic::{AtomicUsize, Ordering::Relaxed}};
-
-pub trait HasSize<E: Output> {
-    fn size (&self) -> &Measure<E>;
-    fn width (&self) -> usize {
-        self.size().w()
-    }
-    fn height (&self) -> usize {
-        self.size().h()
-    }
-}
-
-impl<E: Output, T: Has<Measure<E>>> HasSize<E> for T {
-    fn size (&self) -> &Measure<E> {
-        self.get()
-    }
-}
-
-/// A widget that tracks its render width and height
-#[derive(Default)]
-pub struct Measure<E: Output> {
-    _engine: PhantomData<E>,
-    pub x: Arc<AtomicUsize>,
-    pub y: Arc<AtomicUsize>,
-}
-
-// TODO: 🡘  🡙 ←🡙→ indicator to expand window when too small
-impl<E: Output> Content<E> for Measure<E> {
-    fn render (&self, to: &mut E) {
-        self.x.store(to.area().w().into(), Relaxed);
-        self.y.store(to.area().h().into(), Relaxed);
-    }
-}
-
-impl<E: Output> Clone for Measure<E> {
-    fn clone (&self) -> Self {
-        Self {
-            _engine: Default::default(),
-            x: self.x.clone(),
-            y: self.y.clone(),
-        }
-    }
-}
-
-impl<E: Output> std::fmt::Debug for Measure<E> {
-    fn fmt (&self, f: &mut std::fmt::Formatter<'_>) -> std::result::Result<(), std::fmt::Error> {
-        f.debug_struct("Measure")
-            .field("width",  &self.x)
-            .field("height", &self.y)
-            .finish()
-    }
-}
-
-impl<E: Output> Measure<E> {
-    pub fn new () -> Self {
-        Self {
-            _engine: PhantomData::default(),
-            x: Arc::new(0.into()),
-            y: Arc::new(0.into()),
-        }
-    }
-    pub fn set_w (&self, w: impl Into<usize>) -> &Self {
-        self.x.store(w.into(), Relaxed);
-        self
-    }
-    pub fn set_h (&self, h: impl Into<usize>) -> &Self {
-        self.y.store(h.into(), Relaxed);
-        self
-    }
-    pub fn set_wh (&self, w: impl Into<usize>, h: impl Into<usize>) -> &Self {
-        self.set_w(w);
-        self.set_h(h);
-        self
-    }
-    pub fn w (&self) -> usize {
-        self.x.load(Relaxed)
-    }
-    pub fn h (&self) -> usize {
-        self.y.load(Relaxed)
-    }
-    pub fn wh (&self) -> [usize;2] {
-        [self.w(), self.h()]
-    }
-    pub fn format (&self) -> Arc<str> {
-        format!("{}x{}", self.w(), self.h()).into()
-    }
-    pub fn of <T: Render<E>> (&self, item: T) -> Bsp<Fill<&Self>, T> {
-        Bsp::b(Fill::xy(self), item)
-    }
-}
diff --git a/output/src/space/size.rs b/output/src/space/size.rs
deleted file mode 100644
index f9e2d19..0000000
--- a/output/src/space/size.rs
+++ /dev/null
@@ -1,40 +0,0 @@
-use crate::*;
-use std::fmt::Debug;
-
-pub trait Size<N: Coordinate>: From<[N;2]> + Debug + Copy {
-    fn x (&self) -> N;
-    fn y (&self) -> N;
-    fn w (&self) -> N { self.x() }
-    fn h (&self) -> N { self.y() }
-    fn wh (&self) -> [N;2] { [self.x(), self.y()] }
-    fn clip_w (&self, w: N) -> [N;2] { [self.w().min(w), self.h()] }
-    fn clip_h (&self, h: N) -> [N;2] { [self.w(), self.h().min(h)] }
-    fn expect_min (&self, w: N, h: N) -> Usually<&Self> {
-        if self.w() < w || self.h() < h {
-            Err(format!("min {w}x{h}").into())
-        } else {
-            Ok(self)
-        }
-    }
-    fn zero () -> [N;2] {
-        [N::zero(), N::zero()]
-    }
-    fn to_area_pos (&self) -> [N;4] {
-        let [x, y] = self.wh();
-        [x, y, 0.into(), 0.into()]
-    }
-    fn to_area_size (&self) -> [N;4] {
-        let [w, h] = self.wh();
-        [0.into(), 0.into(), w, h]
-    }
-}
-
-impl<N: Coordinate> Size<N> for (N, N) {
-    fn x (&self) -> N { self.0 }
-    fn y (&self) -> N { self.1 }
-}
-
-impl<N: Coordinate> Size<N> for [N;2] {
-    fn x (&self) -> N { self[0] }
-    fn y (&self) -> N { self[1] }
-}
diff --git a/proc/src/proc_view.rs b/proc/src/proc_view.rs
index 5e11c0f..9edf714 100644
--- a/proc/src/proc_view.rs
+++ b/proc/src/proc_view.rs
@@ -50,7 +50,7 @@ impl ToTokens for ViewDef {
 
 impl ViewDef {
     fn generated (&self) -> impl ToTokens {
-        let Self(ViewMeta { output }, ViewImpl { block, exposed }) = self;
+        let Self(ViewMeta { output }, ViewImpl { block, .. }) = self;
         let self_ty  = &block.self_ty;
         let builtins = self.builtins();
         let exposed  = self.exposed();
@@ -74,7 +74,7 @@ impl ViewDef {
     /// Expressions are handled by built-in functions
     /// that operate over constants and symbols.
     fn builtins (&self) -> impl ToTokens {
-        let Self(ViewMeta { output }, ViewImpl { block, exposed }) = self;
+        let Self(ViewMeta { output }, ViewImpl { .. }) = self;
         let builtins = builtins_with_boxes_output(quote! { #output }).map(|builtin|quote! {
             ::tengri::dsl::Val::Exp(_, expr) => return Ok(Some(
                 #builtin::from_dsl(self, expr, ||Box::new("failed to load builtin".into()))?
@@ -85,7 +85,7 @@ impl ViewDef {
     }
     /// Symbols are handled by user-taked functions that take no parameters but `&self`.
     fn exposed (&self) -> impl ToTokens {
-        let Self(ViewMeta { output }, ViewImpl { block, exposed }) = self;
+        let Self(ViewMeta { .. }, ViewImpl { exposed, .. }) = self;
         let exposed = exposed.iter().map(|(key, value)|write_quote(quote! {
             #key => return Ok(Some(self.#value().boxed())),
         }));
diff --git a/tui/src/tui_engine.rs b/tui/src/tui_engine.rs
index b8d60f4..9cd527d 100644
--- a/tui/src/tui_engine.rs
+++ b/tui/src/tui_engine.rs
@@ -3,7 +3,6 @@ use std::time::Duration;
 
 mod tui_buffer; pub use self::tui_buffer::*;
 mod tui_input;  pub use self::tui_input::*;
-mod tui_keys;   pub use self::tui_keys::*;
 mod tui_output; pub use self::tui_output::*;
 mod tui_perf;   pub use self::tui_perf::*;
 
@@ -72,8 +71,7 @@ pub trait TuiRun<R: Render<TuiOut> + Handle<TuiIn> + 'static> {
     fn run (&self, state: &Arc<RwLock<R>>) -> Usually<()>;
 }
 
-impl<T: Render<TuiOut> + Handle<TuiIn> + Send + Sync + 'static>
-TuiRun<T> for Arc<RwLock<Tui>> {
+impl<T: Render<TuiOut> + Handle<TuiIn> + Send + Sync + 'static> TuiRun<T> for Arc<RwLock<Tui>> {
     fn run (&self, state: &Arc<RwLock<T>>) -> Usually<()> {
         let _input_thread = TuiIn::run_input(self, state, Duration::from_millis(100));
         self.write().unwrap().setup()?;
diff --git a/tui/src/tui_engine/tui_input.rs b/tui/src/tui_engine/tui_input.rs
index 9ee6be6..b58c594 100644
--- a/tui/src/tui_engine/tui_input.rs
+++ b/tui/src/tui_engine/tui_input.rs
@@ -4,21 +4,36 @@ use std::thread::{spawn, JoinHandle};
 use crossterm::event::{poll, read};
 
 #[derive(Debug, Clone)]
-pub struct TuiIn(
+pub struct TuiIn {
     /// Exit flag
-    pub Arc<AtomicBool>,
+    pub exited: Arc<AtomicBool>,
     /// Input event
-    pub crossterm::event::Event,
-);
-
-impl Input for TuiIn {
-    type Event = crossterm::event::Event;
-    type Handled = bool;
-    fn event   (&self) -> &crossterm::event::Event { &self.1 }
-    fn is_done (&self) -> bool { self.0.fetch_and(true, Relaxed) }
-    fn done    (&self) { self.0.store(true, Relaxed); }
+    pub event: TuiEvent,
+}
+impl Input for TuiIn {
+    type Event   = TuiEvent;
+    type Handled = bool;
+    fn event   (&self) -> &TuiEvent { &self.event }
+    fn is_done (&self) -> bool { self.exited.fetch_and(true, Relaxed) }
+    fn done    (&self) { self.exited.store(true, Relaxed); }
+}
+#[derive(Debug, Clone, Eq, PartialEq, PartialOrd)]
+pub struct TuiEvent(crossterm::event::Event);
+impl Ord for TuiEvent {
+    fn cmp (&self, other: &Self) -> std::cmp::Ordering {
+        self.partial_cmp(other) .unwrap_or_else(||format!("{:?}", self).cmp(&format!("{other:?}"))) // FIXME perf
+    }
+}
+impl From<crossterm::event::Event> for TuiEvent {
+    fn from (event: crossterm::event::Event) -> Self {
+        Self(event)
+    }
+}
+impl From<Arc<str>> for TuiEvent {
+    fn from (x: Arc<str>) -> Self {
+        TuiEvent(TuiKey::new(x.as_ref()).build().unwrap_or_else(||panic!("invalid key: {x}")))
+    }
 }
-
 impl TuiIn {
     /// Spawn the input thread.
     pub fn run_input <T: Handle<TuiIn> + Send + Sync + 'static> (
@@ -35,7 +50,6 @@ impl TuiIn {
             if poll(timer).is_ok() {
                 let event = read().unwrap();
                 match event {
-
                     crossterm::event::Event::Key(KeyEvent {
                         code:      KeyCode::Char('c'),
                         modifiers: KeyModifiers::CONTROL,
@@ -46,7 +60,8 @@ impl TuiIn {
                     },
                     _ => {
                         let exited = exited.clone();
-                        if let Err(e) = state.write().unwrap().handle(&TuiIn(exited, event)) {
+                        let event  = event.into();
+                        if let Err(e) = state.write().unwrap().handle(&TuiIn { exited, event }) {
                             panic!("{e}")
                         }
                     }
@@ -59,10 +74,101 @@ impl TuiIn {
 //#[cfg(feature = "dsl")]
 //impl DslInput for TuiIn {
     //fn matches_dsl (&self, token: &str) -> bool {
-        //if let Some(event) = KeyMatcher::new(token).build() {
+        //if let Some(event) = TuiKey::new(token).build() {
             //&event == self.event()
         //} else {
             //false
         //}
     //}
 //}
+
+pub struct TuiKey {
+    valid: bool,
+    key:   Option<KeyCode>,
+    mods:  KeyModifiers,
+}
+
+impl TuiKey {
+    pub fn new (token: impl AsRef<str>) -> Self {
+        let token = token.as_ref();
+        if token.len() < 2 {
+            Self { valid: false, key: None, mods: KeyModifiers::NONE }
+        } else if token.chars().next() != Some('@') {
+            Self { valid: false, key: None, mods: KeyModifiers::NONE }
+        } else {
+            Self { valid: true, key: None, mods: KeyModifiers::NONE }.next(&token[1..])
+        }
+    }
+    pub fn build (self) -> Option<Event> {
+        if self.valid && self.key.is_some() {
+            Some(Event::Key(KeyEvent::new(self.key.unwrap(), self.mods)))
+        } else {
+            None
+        }
+    }
+    fn next (mut self, token: &str) -> Self {
+        let mut tokens = token.split('-').peekable();
+        while let Some(token) = tokens.next() {
+            if tokens.peek().is_some() {
+                match token {
+                    "ctrl"  | "Ctrl"  | "c" | "C" => self.mods |= KeyModifiers::CONTROL,
+                    "alt"   | "Alt"   | "m" | "M" => self.mods |= KeyModifiers::ALT,
+                    "shift" | "Shift" | "s" | "S" => {
+                        self.mods |= KeyModifiers::SHIFT;
+                        // + TODO normalize character case, BackTab, etc.
+                    },
+                    _ => panic!("unknown modifier {token}"),
+                }
+            } else {
+                self.key = if token.len() == 1 {
+                    Some(KeyCode::Char(token.chars().next().unwrap()))
+                } else {
+                    Some(Self::named_key(token).unwrap_or_else(||panic!("unknown character {token}")))
+                }
+            }
+        }
+        self
+    }
+    fn named_key (token: &str) -> Option<KeyCode> {
+        use KeyCode::*;
+        Some(match token {
+            "up"                => Up,
+            "down"              => Down,
+            "left"              => Left,
+            "right"             => Right,
+            "esc"    | "escape" => Esc,
+            "enter"  | "return" => Enter,
+            "delete" | "del"    => Delete,
+            "tab"               => Tab,
+            "space"             => Char(' '),
+            "comma"             => Char(','),
+            "period"            => Char('.'),
+            "plus"              => Char('+'),
+            "minus" | "dash"    => Char('-'),
+            "equal" | "equals"  => Char('='),
+            "underscore"        => Char('_'),
+            "backtick"          => Char('`'),
+            "lt"                => Char('<'),
+            "gt"                => Char('>'),
+            "cbopen"  | "openbrace"  => Char('{'),
+            "cbclose" | "closebrace" => Char('}'),
+            "bropen"  | "openbracket"  => Char('['),
+            "brclose" | "closebracket" => Char(']'),
+            "pgup" | "pageup"   => PageUp,
+            "pgdn" | "pagedown" => PageDown, 
+            "f1"                => F(1),
+            "f2"                => F(2),
+            "f3"                => F(3),
+            "f4"                => F(4),
+            "f5"                => F(5),
+            "f6"                => F(6),
+            "f7"                => F(7),
+            "f8"                => F(8),
+            "f9"                => F(9),
+            "f10"               => F(10),
+            "f11"               => F(11),
+            "f12"               => F(12),
+            _ => return None,
+        })
+    }
+}
diff --git a/tui/src/tui_engine/tui_keys.rs b/tui/src/tui_engine/tui_keys.rs
deleted file mode 100644
index cda5899..0000000
--- a/tui/src/tui_engine/tui_keys.rs
+++ /dev/null
@@ -1,92 +0,0 @@
-use crate::*;
-
-pub struct KeyMatcher {
-    valid: bool,
-    key:   Option<KeyCode>,
-    mods:  KeyModifiers,
-}
-
-impl KeyMatcher {
-    pub fn new (token: impl AsRef<str>) -> Self {
-        let token = token.as_ref();
-        if token.len() < 2 {
-            Self { valid: false, key: None, mods: KeyModifiers::NONE }
-        } else if token.chars().next() != Some('@') {
-            Self { valid: false, key: None, mods: KeyModifiers::NONE }
-        } else {
-            Self { valid: true, key: None, mods: KeyModifiers::NONE }.next(&token[1..])
-        }
-    }
-    pub fn build (self) -> Option<Event> {
-        if self.valid && self.key.is_some() {
-            Some(Event::Key(KeyEvent::new(self.key.unwrap(), self.mods)))
-        } else {
-            None
-        }
-    }
-    fn next (mut self, token: &str) -> Self {
-        let mut tokens = token.split('-').peekable();
-        while let Some(token) = tokens.next() {
-            if tokens.peek().is_some() {
-                match token {
-                    "ctrl"  | "Ctrl"  | "c" | "C" => self.mods |= KeyModifiers::CONTROL,
-                    "alt"   | "Alt"   | "m" | "M" => self.mods |= KeyModifiers::ALT,
-                    "shift" | "Shift" | "s" | "S" => {
-                        self.mods |= KeyModifiers::SHIFT;
-                        // + TODO normalize character case, BackTab, etc.
-                    },
-                    _ => panic!("unknown modifier {token}"),
-                }
-            } else {
-                self.key = if token.len() == 1 {
-                    Some(KeyCode::Char(token.chars().next().unwrap()))
-                } else {
-                    Some(Self::named_key(token).unwrap_or_else(||panic!("unknown character {token}")))
-                }
-            }
-        }
-        self
-    }
-    fn named_key (token: &str) -> Option<KeyCode> {
-        use KeyCode::*;
-        Some(match token {
-            "up"                => Up,
-            "down"              => Down,
-            "left"              => Left,
-            "right"             => Right,
-            "esc"    | "escape" => Esc,
-            "enter"  | "return" => Enter,
-            "delete" | "del"    => Delete,
-            "tab"               => Tab,
-            "space"             => Char(' '),
-            "comma"             => Char(','),
-            "period"            => Char('.'),
-            "plus"              => Char('+'),
-            "minus" | "dash"    => Char('-'),
-            "equal" | "equals"  => Char('='),
-            "underscore"        => Char('_'),
-            "backtick"          => Char('`'),
-            "lt"                => Char('<'),
-            "gt"                => Char('>'),
-            "cbopen"  | "openbrace"  => Char('{'),
-            "cbclose" | "closebrace" => Char('}'),
-            "bropen"  | "openbracket"  => Char('['),
-            "brclose" | "closebracket" => Char(']'),
-            "pgup" | "pageup"   => PageUp,
-            "pgdn" | "pagedown" => PageDown, 
-            "f1"                => F(1),
-            "f2"                => F(2),
-            "f3"                => F(3),
-            "f4"                => F(4),
-            "f5"                => F(5),
-            "f6"                => F(6),
-            "f7"                => F(7),
-            "f8"                => F(8),
-            "f9"                => F(9),
-            "f10"               => F(10),
-            "f11"               => F(11),
-            "f12"               => F(12),
-            _ => return None,
-        })
-    }
-}