diff --git a/input/input.rs b/input/input.rs
index b251232..aa72db1 100644
--- a/input/input.rs
+++ b/input/input.rs
@@ -19,6 +19,37 @@ pub trait Input: Sized {
     fn done (&self);
 }
 
+/// Define a trait an implement it for various mutation-enabled wrapper types. */
+#[macro_export] macro_rules! flex_trait_mut (
+    ($Trait:ident $(<$($A:ident:$T:ident),+>)? {
+        $(fn $fn:ident (&mut $self:ident $(, $arg:ident:$ty:ty)*) -> $ret:ty $body:block)*
+    })=>{
+        pub trait $Trait $(<$($A: $T),+>)? {
+            $(fn $fn (&mut $self $(,$arg:$ty)*) -> $ret $body)*
+        }
+        impl<$($($A: $T,)+)? _T_: $Trait $(<$($A),+>)?> $Trait $(<$($A),+>)? for &mut _T_ {
+            $(fn $fn (&mut $self $(,$arg:$ty)*) -> $ret { (*$self).$fn($($arg),*) })*
+        }
+        impl<$($($A: $T,)+)? _T_: $Trait $(<$($A),+>)?> $Trait $(<$($A),+>)? for Option<_T_> {
+            $(fn $fn (&mut $self $(,$arg:$ty)*) -> $ret {
+                if let Some(this) = $self { this.$fn($($arg),*) } else { Ok(None) }
+            })*
+        }
+        impl<$($($A: $T,)+)? _T_: $Trait $(<$($A),+>)?> $Trait $(<$($A),+>)? for ::std::sync::Mutex<_T_> {
+            $(fn $fn (&mut $self $(,$arg:$ty)*) -> $ret { $self.get_mut().unwrap().$fn($($arg),*) })*
+        }
+        impl<$($($A: $T,)+)? _T_: $Trait $(<$($A),+>)?> $Trait $(<$($A),+>)? for ::std::sync::Arc<::std::sync::Mutex<_T_>> {
+            $(fn $fn (&mut $self $(,$arg:$ty)*) -> $ret { $self.lock().unwrap().$fn($($arg),*) })*
+        }
+        impl<$($($A: $T,)+)? _T_: $Trait $(<$($A),+>)?> $Trait $(<$($A),+>)? for ::std::sync::RwLock<_T_> {
+            $(fn $fn (&mut $self $(,$arg:$ty)*) -> $ret { $self.write().unwrap().$fn($($arg),*) })*
+        }
+        impl<$($($A: $T,)+)? _T_: $Trait $(<$($A),+>)?> $Trait $(<$($A),+>)? for ::std::sync::Arc<::std::sync::RwLock<_T_>> {
+            $(fn $fn (&mut $self $(,$arg:$ty)*) -> $ret { $self.write().unwrap().$fn($($arg),*) })*
+        }
+    };
+);
+
 flex_trait_mut!(Handle <E: Input> {
     fn handle (&mut self, _input: &E) -> Perhaps<E::Handled> {
         Ok(None)
diff --git a/output/src/view.rs b/output/src/view.rs
index 8e62c91..fc6411a 100644
--- a/output/src/view.rs
+++ b/output/src/view.rs
@@ -1,30 +1,30 @@
 use crate::*;
-use ::dizzle::{Dsl, DslExpr, DslWord, DslNs};
+use ::dizzle::{Language, Expression, Symbol, Namespace};
 
 pub trait View<O, U> {
-    fn view_expr <'a> (&'a self, output: &mut O, expr: &'a impl DslExpr) -> Usually<U> {
+    fn view_expr <'a> (&'a self, _output: &mut O, expr: &'a impl Expression) -> Usually<U> {
         Err(format!("View::view_expr: no exprs defined: {expr:?}").into())
     }
-    fn view_word <'a> (&'a self, output: &mut O, word: &'a impl DslWord) -> Usually<U> {
+    fn view_word <'a> (&'a self, _output: &mut O, word: &'a impl Symbol) -> Usually<U> {
         Err(format!("View::view_word: no words defined: {word:?}").into())
     }
-    fn view <'a> (&'a self, output: &mut O, dsl: &'a impl Dsl) -> Usually<U> {
+    fn view <'a> (&'a self, output: &mut O, dsl: &'a impl Language) -> Usually<U> {
         if let Ok(Some(expr)) = dsl.expr() {
             self.view_expr(output, &expr)
         } else if let Ok(Some(word)) = dsl.word() {
             self.view_word(output, &word)
         } else {
-            panic!("{dsl:?}: invalid")
+            Err(format!("{dsl:?}: invalid").into())
         }
     }
 }
 
 pub fn evaluate_output_expression <'a, O: Out + 'a, S> (
-    state: &S, output: &mut O, expr: &'a impl DslExpr
+    state: &S, output: &mut O, expr: &'a impl Expression
 ) -> Usually<bool> where
     S: View<O, ()>
-        + for<'b>DslNs<'b, bool>
-        + for<'b>DslNs<'b, O::Unit>
+        + for<'b>Namespace<'b, bool>
+        + for<'b>Namespace<'b, O::Unit>
 {
     // First element of expression is used for dispatch.
     // Dispatch is proto-namespaced using separator character
@@ -43,12 +43,12 @@ pub fn evaluate_output_expression <'a, O: Out + 'a, S> (
     match frags.next() {
 
         Some("when") => output.place(&When::new(
-            state.from(arg0?)?.unwrap(),
+            state.resolve(arg0?)?.unwrap(),
             Thunk::new(move|output: &mut O|state.view(output, &arg1).unwrap())
         )),
 
         Some("either") => output.place(&Either::new(
-            state.from(arg0?)?.unwrap(),
+            state.resolve(arg0?)?.unwrap(),
             Thunk::new(move|output: &mut O|state.view(output, &arg1).unwrap()),
             Thunk::new(move|output: &mut O|state.view(output, &arg2).unwrap())
         )),
@@ -96,9 +96,9 @@ pub fn evaluate_output_expression <'a, O: Out + 'a, S> (
             let arg  = match axis { Some("x") | Some("y") => arg1, Some("xy") | None => arg2, _ => panic!("fixed: unsupported axis {axis:?}") };
             let cb   = Thunk::new(move|output: &mut O|state.view(output, &arg).unwrap());
             match axis {
-                Some("xy") | None => Fixed::XY(state.from(arg0?)?.unwrap(), state.from(arg1?)?.unwrap(), cb),
-                Some("x") => Fixed::X(state.from(arg0?)?.unwrap(), cb),
-                Some("y") => Fixed::Y(state.from(arg0?)?.unwrap(), cb),
+                Some("xy") | None => Fixed::XY(state.resolve(arg0?)?.unwrap(), state.resolve(arg1?)?.unwrap(), cb),
+                Some("x") => Fixed::X(state.resolve(arg0?)?.unwrap(), cb),
+                Some("y") => Fixed::Y(state.resolve(arg0?)?.unwrap(), cb),
                 frag => unimplemented!("fixed/{frag:?} ({expr:?}) ({head:?}) ({:?})",
                     head.src()?.unwrap_or_default().split("/").next())
             }
@@ -109,9 +109,9 @@ pub fn evaluate_output_expression <'a, O: Out + 'a, S> (
             let arg  = match axis { Some("x") | Some("y") => arg1, Some("xy") | None => arg2, _ => panic!("fixed: unsupported axis {axis:?}") };
             let cb   = Thunk::new(move|output: &mut O|state.view(output, &arg).unwrap());
             match axis {
-                Some("xy") | None => Min::XY(state.from(arg0?)?.unwrap(), state.from(arg1?)?.unwrap(), cb),
-                Some("x") => Min::X(state.from(arg0?)?.unwrap(), cb),
-                Some("y") => Min::Y(state.from(arg0?)?.unwrap(), cb),
+                Some("xy") | None => Min::XY(state.resolve(arg0?)?.unwrap(), state.resolve(arg1?)?.unwrap(), cb),
+                Some("x") => Min::X(state.resolve(arg0?)?.unwrap(), cb),
+                Some("y") => Min::Y(state.resolve(arg0?)?.unwrap(), cb),
                 frag => unimplemented!("min/{frag:?}")
             }
         }),
@@ -121,9 +121,9 @@ pub fn evaluate_output_expression <'a, O: Out + 'a, S> (
             let arg  = match axis { Some("x") | Some("y") => arg1, Some("xy") | None => arg2, _ => panic!("fixed: unsupported axis {axis:?}") };
             let cb   = Thunk::new(move|output: &mut O|state.view(output, &arg).unwrap());
             match axis {
-                Some("xy") | None => Max::XY(state.from(arg0?)?.unwrap(), state.from(arg1?)?.unwrap(), cb),
-                Some("x") => Max::X(state.from(arg0?)?.unwrap(), cb),
-                Some("y") => Max::Y(state.from(arg0?)?.unwrap(), cb),
+                Some("xy") | None => Max::XY(state.resolve(arg0?)?.unwrap(), state.resolve(arg1?)?.unwrap(), cb),
+                Some("x") => Max::X(state.resolve(arg0?)?.unwrap(), cb),
+                Some("y") => Max::Y(state.resolve(arg0?)?.unwrap(), cb),
                 frag => unimplemented!("max/{frag:?}")
             }
         }),
@@ -133,9 +133,9 @@ pub fn evaluate_output_expression <'a, O: Out + 'a, S> (
             let arg  = match axis { Some("x") | Some("y") => arg1, Some("xy") | None => arg2, _ => panic!("fixed: unsupported axis {axis:?}") };
             let cb   = Thunk::new(move|output: &mut O|state.view(output, &arg).unwrap());
             match axis {
-                Some("xy") | None => Push::XY(state.from(arg0?)?.unwrap(), state.from(arg1?)?.unwrap(), cb),
-                Some("x") => Push::X(state.from(arg0?)?.unwrap(), cb),
-                Some("y") => Push::Y(state.from(arg0?)?.unwrap(), cb),
+                Some("xy") | None => Push::XY(state.resolve(arg0?)?.unwrap(), state.resolve(arg1?)?.unwrap(), cb),
+                Some("x") => Push::X(state.resolve(arg0?)?.unwrap(), cb),
+                Some("y") => Push::Y(state.resolve(arg0?)?.unwrap(), cb),
                 frag => unimplemented!("push/{frag:?}")
             }
         }),
diff --git a/tui/src/tui_engine.rs b/tui/src/tui_engine.rs
index 52a84a0..1c53261 100644
--- a/tui/src/tui_engine.rs
+++ b/tui/src/tui_engine.rs
@@ -88,7 +88,7 @@ impl<T: TuiWidget + 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()?;
-        let render_thread = TuiOut::run_output(self, state, Duration::from_millis(10));
+        let render_thread = TuiOut::run_output(self, state, Duration::from_millis(10))?;
         match render_thread.join() {
             Ok(result) => {
                 self.write().unwrap().teardown()?;
@@ -96,7 +96,7 @@ impl<T: TuiWidget + Send + Sync + 'static> TuiRun<T> for Arc<RwLock<Tui>> {
             },
             Err(error) => {
                 self.write().unwrap().teardown()?;
-                panic!("\n\rDraw thread failed: {error:?}.\n\r")
+                panic!("\n\rDraw thread failed: error={error:?}.\n\r")
             },
         }
         Ok(())
@@ -105,22 +105,22 @@ impl<T: TuiWidget + Send + Sync + 'static> TuiRun<T> for Arc<RwLock<Tui>> {
 
 #[cfg(feature = "dsl")] 
 pub fn evaluate_output_expression_tui <'a, S> (
-    state: &S, mut output: &mut TuiOut, expr: impl DslExpr + 'a
+    state: &S, output: &mut TuiOut, expr: impl Expression + 'a
 ) -> Usually<bool> where
     S: View<TuiOut, ()>
-        + for<'b>DslNs<'b, bool>
-        + for<'b>DslNs<'b, u16>
-        + for<'b>DslNs<'b, Color>
+        + for<'b>Namespace<'b, bool>
+        + for<'b>Namespace<'b, u16>
+        + for<'b>Namespace<'b, Color>
 {
     // See `tengri_output::evaluate_output_expression`
     let head = expr.head()?;
     let mut frags = head.src()?.unwrap_or_default().split("/");
-    let args = expr.tail();
-    let arg0 = args.head();
+    let args  = expr.tail();
+    let arg0  = args.head();
     let tail0 = args.tail();
-    let arg1 = tail0.head();
+    let arg1  = tail0.head();
     let tail1 = tail0.tail();
-    let arg2 = tail1.head();
+    let _arg2 = tail1.head();
     match frags.next() {
 
         Some("text") => if let Some(src) = args?.src()? { output.place(&src) },
@@ -128,7 +128,7 @@ pub fn evaluate_output_expression_tui <'a, S> (
         Some("fg") => {
             let arg0 = arg0?.expect("fg: expected arg 0 (color)");
             output.place(&Tui::fg(
-                DslNs::<Color>::from(state, arg0)?.unwrap_or_else(||panic!("fg: {arg0:?}: not a color")),
+                Namespace::<Color>::resolve(state, arg0)?.unwrap_or_else(||panic!("fg: {arg0:?}: not a color")),
                 Thunk::new(move|output: &mut TuiOut|state.view(output, &arg1).unwrap()),
             ))
         },
@@ -136,7 +136,7 @@ pub fn evaluate_output_expression_tui <'a, S> (
         Some("bg") => {
             let arg0 = arg0?.expect("bg: expected arg 0 (color)");
             output.place(&Tui::bg(
-                DslNs::<Color>::from(state, arg0)?.unwrap_or_else(||panic!("bg: {arg0:?}: not a color")),
+                Namespace::<Color>::resolve(state, arg0)?.unwrap_or_else(||panic!("bg: {arg0:?}: not a color")),
                 Thunk::new(move|output: &mut TuiOut|state.view(output, &arg1).unwrap()),
             ))
         },
diff --git a/tui/src/tui_engine/tui_event.rs b/tui/src/tui_engine/tui_event.rs
index 1245a30..ead67fc 100644
--- a/tui/src/tui_engine/tui_event.rs
+++ b/tui/src/tui_engine/tui_event.rs
@@ -11,7 +11,7 @@ impl TuiEvent {
         Self(event)
     }
     #[cfg(feature = "dsl")]
-    pub fn from_dsl (dsl: impl Dsl) -> Perhaps<Self> {
+    pub fn from_dsl (dsl: impl Language) -> Perhaps<Self> {
         Ok(TuiKey::from_dsl(dsl)?.to_crossterm().map(Self))
     }
 }
@@ -19,7 +19,7 @@ pub struct TuiKey(Option<KeyCode>, KeyModifiers);
 impl TuiKey {
     const SPLIT: char = '/';
     #[cfg(feature = "dsl")]
-    pub fn from_dsl (dsl: impl Dsl) -> Usually<Self> {
+    pub fn from_dsl (dsl: impl Language) -> Usually<Self> {
         if let Some(word) = dsl.word()? {
             let word = word.trim();
             Ok(if word == ":char" {