diff --git a/engine/src/engine.rs b/engine/src/engine.rs
index 713c802f..4371e7e6 100644
--- a/engine/src/engine.rs
+++ b/engine/src/engine.rs
@@ -126,6 +126,18 @@ pub trait Area<N: Coordinate> {
     #[inline] fn center (&self) -> [N;2] {
         [self.x() + self.w()/2.into(), self.y() + self.h()/2.into()]
     }
+    #[inline] fn center_x (&self, n: N) -> [N;4] {
+        let [x, y, w, h] = self.xywh();
+        [x + w / 2.into() - n, y + h / 2.into(), n, 1.into()]
+    }
+    #[inline] fn center_y (&self, m: N) -> [N;4] {
+        let [x, y, w, h] = self.xywh();
+        [x + w / 2.into(), y + h / 2.into() - m, 1.into(), m]
+    }
+    #[inline] fn center_xy (&self, [n, m]: [N;2]) -> [N;4] {
+        let [x, y, w, h] = self.xywh();
+        [x + w / 2.into() - n, y + h / 2.into() - n - m, n, m]
+    }
     #[inline] fn centered (&self) -> [N;2] {
         [self.x().minus(self.w()/2.into()), self.y().minus(self.h()/2.into())]
     }
diff --git a/engine/src/lib.rs b/engine/src/lib.rs
index 00fb8356..9a89169b 100644
--- a/engine/src/lib.rs
+++ b/engine/src/lib.rs
@@ -13,6 +13,10 @@ pub type Usually<T> = Result<T, Box<dyn Error>>;
 /// Standard optional result type.
 pub type Perhaps<T> = Result<Option<T>, Box<dyn Error>>;
 
+#[cfg(test)] #[test] fn test_dimensions () {
+    assert_eq!(Area::center(&[10u16, 10, 20, 20]), [20, 20]);
+}
+
 #[cfg(test)] #[test] fn test_stub_engine () -> Usually<()> {
     struct TestEngine(bool);
     struct TestInput(bool);
@@ -46,11 +50,11 @@ pub type Perhaps<T> = Result<Option<T>, Box<dyn Error>>;
         fn area_mut (&mut self) -> &mut [u16;4] {
             &mut self.0
         }
-        fn place (&mut self, _: [u16;4], _: &impl Layout<TestEngine>) {
+        fn place (&mut self, _: [u16;4], _: &impl Content<TestEngine>) {
             ()
         }
     }
-    impl Layout<TestEngine> for String {
+    impl Content<TestEngine> for String {
         fn render (&self, to: &mut TestOutput) {
             to.area_mut().set_w(self.len() as u16);
         }
@@ -62,8 +66,8 @@ pub type Perhaps<T> = Result<Option<T>, Box<dyn Error>>;
     use crate::tui::*;
     use std::sync::{Arc, RwLock};
     struct TestComponent(String);
-    impl Layout<Tui> for TestComponent {
-        fn layout (&self) -> Option<impl Layout<Tui>> {
+    impl Content<Tui> for TestComponent {
+        fn content (&self) -> Option<impl Content<Tui>> {
             Some(self.0.as_str())
         }
     }
diff --git a/engine/src/tui/tui_output.rs b/engine/src/tui/tui_output.rs
index ceab4c8a..387cc5dd 100644
--- a/engine/src/tui/tui_output.rs
+++ b/engine/src/tui/tui_output.rs
@@ -71,10 +71,7 @@ impl TuiOut {
 
 impl Content<Tui> for &str {
     fn layout (&self, to: [u16;4]) -> [u16;4] {
-        let w = self.chars().count() as u16;
-        let y = to.y() + to.h() / 2;
-        let x = (to.x() + to.w() / 2).minus(w / 2);
-        [x, y, w, 1]
+        to.center_x(self.chars().count() as u16)
     }
     fn render (&self, to: &mut TuiOut) {
         to.blit(self, to.area.x(), to.area.y(), None)
@@ -83,10 +80,7 @@ impl Content<Tui> for &str {
 
 impl Content<Tui> for String {
     fn layout (&self, to: [u16;4]) -> [u16;4] {
-        let w = self.chars().count() as u16;
-        let y = to.y() + to.h() / 2;
-        let x = (to.x() + to.w() / 2).minus(w / 2);
-        [x, y, w, 1]
+        to.center_x(self.chars().count() as u16)
     }
     fn render (&self, to: &mut TuiOut) {
         to.blit(self, to.area.x(), to.area.y(), None)
diff --git a/layout/src/direction.rs b/layout/src/direction.rs
index 8c189e3f..1b1f7c14 100644
--- a/layout/src/direction.rs
+++ b/layout/src/direction.rs
@@ -20,7 +20,7 @@ impl Direction {
             Self::East  => Self::South,
         }
     }
-    /// Return next direction counterclockwise
+    /// Return next direction counterclockwise01. 
     pub fn ccw (&self) -> Self {
         match self {
             Self::North => Self::West,
diff --git a/layout/src/lib.rs b/layout/src/lib.rs
index 5f4455be..0f293e73 100644
--- a/layout/src/lib.rs
+++ b/layout/src/lib.rs
@@ -14,12 +14,18 @@ pub(crate) use std::marker::PhantomData;
 
 #[cfg(test)] #[test] fn test_layout () -> Usually<()> {
     use crate::tui::Tui;
+
     let area: [u16;4] = [10, 10, 20, 20];
     let unit = ();
-     // should be independent over E, isn't
-    assert_eq!(Content::<Tui>::layout(&unit, area), [15, 15, 0, 0]);
-    assert_eq!(Fill::<Tui, _>::x(unit).layout(area), [10, 15, 20, 0]);
-    assert_eq!(Fill::<Tui, _>::y(unit).layout(area), [15, 10, 0, 20]);
+
+    assert_eq!(Content::<Tui>::layout(&unit, area), [20, 20, 0, 0]);
+
+    assert_eq!(Fill::<Tui, _>::x(unit).layout(area), [10, 20, 20, 0]);
+    assert_eq!(Fill::<Tui, _>::y(unit).layout(area), [20, 10, 0, 20]);
     assert_eq!(Fill::<Tui, _>::xy(unit).layout(area), area);
+
+    assert_eq!(Align::<Tui, _>::c(unit).layout(area), [20, 20, 0, 0]);
+    assert_eq!(Align::<Tui, _>::c("  ").layout(area), [20, 20, 0, 0]);
+
     Ok(())
 }