diff --git a/src/length.rs b/src/length.rs
index 19927e1..bbda7fa 100644
--- a/src/length.rs
+++ b/src/length.rs
@@ -9,8 +9,9 @@
 //! A one-dimensional length, tagged with its units.
 
 use scale_factor::ScaleFactor;
+use num::Zero;
 
-use std::num::{NumCast, cast, Zero};
+use std::num::{NumCast, cast};
 
 /// A one-dimensional distance, with value represented by `T` and unit of measurement `Unit`.
 ///
@@ -104,14 +105,10 @@ impl<Unit, T: Clone + Ord> Ord for Length<Unit, T> {
     fn cmp(&self, other: &Length<Unit, T>) -> Ordering { self.get().cmp(&other.get()) }
 }
 
-impl<Unit, T: Clone + Zero> Zero for Length<Unit, T> {
+impl<Unit, T: Zero> Zero for Length<Unit, T> {
     fn zero() -> Length<Unit, T> {
         Length(Zero::zero())
     }
-
-    fn is_zero(&self) -> bool {
-        self.get().is_zero()
-    }
 }
 
 #[cfg(test)]
diff --git a/src/lib.rs b/src/lib.rs
index 891e90f..f873bf8 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -31,9 +31,9 @@ pub mod approxeq;
 pub mod length;
 pub mod matrix;
 pub mod matrix2d;
+pub mod num;
 pub mod point;
 pub mod rect;
 pub mod scale_factor;
 pub mod side_offsets;
 pub mod size;
-
diff --git a/src/matrix.rs b/src/matrix.rs
index f82a396..9e92b15 100644
--- a/src/matrix.rs
+++ b/src/matrix.rs
@@ -8,8 +8,10 @@
 // except according to those terms.
 
 use approxeq::ApproxEq;
+use num::{One, Zero};
+
 use std::num;
-use std::num::{NumCast, One, Zero};
+use std::num::NumCast;
 
 pub fn Matrix4<T:Add<T,T> + Clone + ApproxEq<T> + Mul<T,T> + One + Zero>(
         m11: T, m12: T, m13: T, m14: T,
diff --git a/src/matrix2d.rs b/src/matrix2d.rs
index 7ed91d3..7013a9d 100644
--- a/src/matrix2d.rs
+++ b/src/matrix2d.rs
@@ -7,7 +7,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use std::num::{One, Zero};
+use num::{One, Zero};
 
 pub struct Matrix2D<T> {
     m11: T, m12: T,
@@ -31,7 +31,7 @@ impl<T:Add<T,T> + Clone + Mul<T,T> + One + Zero> Matrix2D<T> {
                       m.m21*self.m12 + m.m22*self.m22,
                       m.m31*self.m11 + m.m32*self.m21 + self.m31,
                       m.m31*self.m12 + m.m32*self.m22 + self.m32)
-    } 
+    }
 
     pub fn translate(&self, x: T, y: T) -> Matrix2D<T> {
          let (_0, _1): (T, T) = (Zero::zero(), One::one());
@@ -53,14 +53,13 @@ impl<T:Add<T,T> + Clone + Mul<T,T> + One + Zero> Matrix2D<T> {
                              _0.clone(), _1.clone(),
                              _0.clone(), _0.clone());
     }
-        
+
     pub fn to_array(&self) -> [T, ..6] {
         [
             self.m11.clone(), self.m12.clone(),
             self.m21.clone(), self.m22.clone(),
             self.m31.clone(), self.m32.clone()
         ]
-    } 
-
+    }
 }
 
diff --git a/src/num.rs b/src/num.rs
new file mode 100644
index 0000000..b81dcd9
--- /dev/null
+++ b/src/num.rs
@@ -0,0 +1,50 @@
+// Copyright 2014 The Servo Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+//! A one-dimensional length, tagged with its units.
+
+use std::num::Int;
+
+
+pub trait Zero {
+    fn zero() -> Self;
+}
+
+impl<T: Int> Zero for T {
+    #[inline]
+    fn zero() -> T { Int::zero() }
+}
+
+impl Zero for f32 {
+    #[inline]
+    fn zero() -> f32 { 0. }
+}
+
+impl Zero for f64 {
+    #[inline]
+    fn zero() -> f64 { 0. }
+}
+
+pub trait One {
+    fn one() -> Self;
+}
+
+impl<T: Int> One for T {
+    #[inline]
+    fn one() -> T { Int::one() }
+}
+
+impl One for f32 {
+    #[inline]
+    fn one() -> f32 { 1. }
+}
+
+impl One for f64 {
+    #[inline]
+    fn one() -> f64 { 1. }
+}
diff --git a/src/point.rs b/src/point.rs
index 6960e60..434b8c1 100644
--- a/src/point.rs
+++ b/src/point.rs
@@ -9,9 +9,10 @@
 
 use length::Length;
 use size::Size2D;
+use num::Zero;
 
 use std::fmt;
-use std::num::{NumCast, Zero};
+use std::num::NumCast;
 
 #[deriving(Clone, Decodable, Encodable, Eq, Hash, PartialEq)]
 pub struct Point2D<T> {
@@ -19,14 +20,10 @@ pub struct Point2D<T> {
     pub y: T
 }
 
-impl<T: Zero + Clone> Zero for Point2D<T> {
-    fn zero() -> Point2D<T> {
+impl<T: Zero> Point2D<T> {
+    pub fn zero() -> Point2D<T> {
         Point2D { x: Zero::zero(), y: Zero::zero() }
     }
-
-    fn is_zero(&self) -> bool {
-        self.x.is_zero() && self.y.is_zero()
-    }
 }
 
 impl<T: fmt::Show> fmt::Show for Point2D<T> {
@@ -35,7 +32,7 @@ impl<T: fmt::Show> fmt::Show for Point2D<T> {
     }
 }
 
-pub fn Point2D<T:Clone>(x: T, y: T) -> Point2D<T> {
+pub fn Point2D<T>(x: T, y: T) -> Point2D<T> {
     Point2D {x: x, y: y}
 }
 
diff --git a/src/rect.rs b/src/rect.rs
index 348f86e..776f0e0 100644
--- a/src/rect.rs
+++ b/src/rect.rs
@@ -8,12 +8,13 @@
 // except according to those terms.
 
 use length::Length;
+use num::Zero;
 
 use point::Point2D;
 use size::Size2D;
-use std::cmp::{PartialEq, PartialOrd};
+use std::cmp::PartialOrd;
 use std::fmt;
-use std::num::{NumCast, Zero};
+use std::num::NumCast;
 
 #[deriving(Clone, Decodable, Encodable, PartialEq)]
 pub struct Rect<T> {
@@ -126,16 +127,16 @@ impl<Scale, T: Clone + Mul<Scale,T>> Rect<T> {
     }
 }
 
-impl<T:Clone + Zero> Rect<T> {
+impl<T: PartialEq + Zero> Rect<T> {
     pub fn zero() -> Rect<T> {
         Rect {
-            origin: Zero::zero(),
+            origin: Point2D::zero(),
             size: Size2D::zero(),
         }
     }
 
     pub fn is_empty(&self) -> bool {
-        self.size.is_empty()
+        self.size == Size2D::zero()
     }
 }
 
diff --git a/src/scale_factor.rs b/src/scale_factor.rs
index a010ccf..8b9a3f9 100644
--- a/src/scale_factor.rs
+++ b/src/scale_factor.rs
@@ -8,7 +8,8 @@
 // except according to those terms.
 //! A type-checked scaling factor between units.
 
-use std::num::{NumCast, cast, One};
+use num::One;
+use std::num::{NumCast, cast};
 
 /// A scaling factor between two different units of measurement.
 ///
diff --git a/src/side_offsets.rs b/src/side_offsets.rs
index bf84dff..286fe3d 100644
--- a/src/side_offsets.rs
+++ b/src/side_offsets.rs
@@ -10,7 +10,8 @@
 //! A group of side offsets, which correspond to top/left/bottom/right for borders, padding,
 //! and margins in CSS.
 
-use std::num::{Num, NumCast, Zero};
+use num::Zero;
+use std::num::Num;
 
 /// A group of side offsets, which correspond to top/left/bottom/right for borders, padding,
 /// and margins in CSS.
@@ -60,8 +61,8 @@ impl<T:Num> Add<SideOffsets2D<T>, SideOffsets2D<T>> for SideOffsets2D<T> {
     }
 }
 
-impl<T:Num> Zero for SideOffsets2D<T> {
-    fn zero() -> SideOffsets2D<T> {
+impl<T: Zero> SideOffsets2D<T> {
+    pub fn zero() -> SideOffsets2D<T> {
         SideOffsets2D {
             top: Zero::zero(),
             right: Zero::zero(),
@@ -69,10 +70,6 @@ impl<T:Num> Zero for SideOffsets2D<T> {
             left: Zero::zero(),
         }
     }
-
-    fn is_zero(&self) -> bool {
-        self.top.is_zero() && self.right.is_zero() && self.bottom.is_zero() && self.left.is_zero()
-    }
 }
 
 /// A SIMD enabled version of SideOffsets2D specialized for i32.
@@ -123,26 +120,26 @@ impl Add<SideOffsets2DSimdI32, SideOffsets2DSimdI32> for SideOffsets2DSimdI32 {
     }
 }
 
-impl Zero for SideOffsets2DSimdI32 {
+impl SideOffsets2DSimdI32 {
     #[inline]
-    fn zero() -> SideOffsets2DSimdI32 {
+    pub fn zero() -> SideOffsets2DSimdI32 {
         SideOffsets2DSimdI32 {
-            top: Zero::zero(),
-            bottom: Zero::zero(),
-            right: Zero::zero(),
-            left: Zero::zero(),
+            top: 0,
+            bottom: 0,
+            right: 0,
+            left: 0,
         }
     }
 
     #[cfg(not(target_arch = "x86_64"))]
     #[inline]
-    fn is_zero(&self) -> bool {
-        self.top.is_zero() && self.right.is_zero() && self.bottom.is_zero() && self.left.is_zero()
+    pub fn is_zero(&self) -> bool {
+        self.top == 0 && self.right == 0 && self.bottom == 0 && self.left == 0
     }
 
     #[cfg(target_arch = "x86_64")]
     #[inline]
-    fn is_zero(&self) -> bool {
+    pub fn is_zero(&self) -> bool {
         let is_zero: bool;
         unsafe {
             asm! {
diff --git a/src/size.rs b/src/size.rs
index 0025539..02f8809 100644
--- a/src/size.rs
+++ b/src/size.rs
@@ -8,10 +8,10 @@
 // except according to those terms.
 
 use length::Length;
+use num::Zero;
 
-use std::cmp::PartialEq;
 use std::fmt;
-use std::num::{NumCast, Zero};
+use std::num::NumCast;
 
 #[deriving(Clone, Decodable, Encodable, PartialEq)]
 pub struct Size2D<T> {
@@ -36,17 +36,13 @@ impl<T:Clone + Mul<T,U>, U> Size2D<T> {
     pub fn area(&self) -> U { self.width * self.height }
 }
 
-impl<T:Clone + Zero> Size2D<T> {
+impl<T: Zero> Size2D<T> {
     pub fn zero() -> Size2D<T> {
         Size2D {
             width: Zero::zero(),
             height: Zero::zero(),
         }
     }
-
-    pub fn is_empty(&self) -> bool {
-        self.width.is_zero() || self.height.is_zero()
-    }
 }
 
 impl<Scale, T0: Mul<Scale, T1>, T1: Clone> Mul<Scale, Size2D<T1>> for Size2D<T0> {