diff --git a/src/dashboard.rs b/src/dashboard.rs
index eeb9caa..7ad7d70 100644
--- a/src/dashboard.rs
+++ b/src/dashboard.rs
@@ -3,7 +3,7 @@
 
 #![allow(clippy::type_complexity)]
 
-use super::{Player, Velocity};
+use super::{physics, Player};
 use bevy::prelude::*;
 
 #[derive(Component, Debug)]
@@ -91,7 +91,7 @@ fn spawn_dashboard(mut commands: Commands, asset_server: Res<AssetServer>) {
 }
 
 fn update_speedo(
-    player: Query<(&Velocity, With<Player>)>,
+    player: Query<(&physics::Velocity, With<Player>)>,
     mut speedo: Query<(&mut Transform, With<Speedometer>)>,
 ) {
     let (vp, _) = player.single();
diff --git a/src/main.rs b/src/main.rs
index c970717..ef3f61d 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -3,26 +3,19 @@
 
 #![allow(clippy::type_complexity)]
 
-use bevy::{
-    math::{vec2, vec3},
-    prelude::*,
-    render::camera::ScalingMode,
-    window,
-};
+use bevy::{math::vec3, prelude::*, render::camera::ScalingMode, window};
 use bevy_ecs_tilemap::prelude as ecs_tilemap;
 use clap::Parser;
-use slicetools::*;
 use std::f32::consts::PI;
 
 mod assets;
 mod dashboard;
 mod editor;
 mod mapping;
+mod physics;
 mod tilemap;
 mod util;
 
-use util::IteratorToArrayExt;
-
 #[derive(Clone, Debug, Parser, Resource)]
 #[command(author, version, about, long_about = None)]
 struct Preferences {
@@ -90,13 +83,13 @@ fn main() {
             (
                 handle_keyboard,
                 handle_ai_players,
-                apply_velocity
+                physics::apply_velocity
                     .after(handle_ai_players)
                     .after(handle_keyboard),
-                apply_friction.after(apply_velocity),
-                track_player.after(apply_velocity),
-                collision_detection
-                    .after(apply_velocity)
+                physics::apply_friction.after(physics::apply_velocity),
+                track_player.after(physics::apply_velocity),
+                physics::collision_detection
+                    .after(physics::apply_velocity)
                     .after(handle_keyboard)
                     .after(handle_ai_players),
             ),
@@ -116,27 +109,6 @@ struct Racer {
 #[derive(Component, Default, Debug)]
 struct Track;
 
-#[derive(Component, Debug, Reflect)]
-struct Velocity(Vec2);
-
-#[derive(Component, Clone, Debug, Reflect)]
-struct Angle(f32);
-
-impl Angle {
-    fn normalize(&mut self) {
-        while self.0 > PI {
-            self.0 -= 2.0 * PI;
-        }
-        while self.0 < -PI {
-            self.0 += 2.0 * PI;
-        }
-    }
-
-    fn to_quat(&self) -> Quat {
-        Quat::from_rotation_z(self.0 - PI / 2.0)
-    }
-}
-
 fn spawn_camera(mut commands: Commands) {
     let mut camera = Camera2dBundle::default();
     // Request a constant width projection. 24 is the width in world units.
@@ -171,8 +143,8 @@ fn spawn_player(
     commands.spawn((
         Player,
         Racer::default(),
-        Angle(0.0),
-        Velocity(Vec2::new(0.0, 20.0)),
+        physics::Angle(0.0),
+        physics::Velocity(Vec2::new(0.0, 20.0)),
         SpriteSheetBundle {
             texture_atlas: texture_atlas.add(atlas),
             transform: Transform {
@@ -196,8 +168,8 @@ fn spawn_ai_players(
 
     commands.spawn((
         Racer::default(),
-        Angle(PI / 12.0),
-        Velocity(Vec2::new(0.0, 20.0)),
+        physics::Angle(PI / 12.0),
+        physics::Velocity(Vec2::new(0.0, 20.0)),
         SpriteSheetBundle {
             texture_atlas: texture_atlas.add(atlas),
             transform: Transform {
@@ -214,8 +186,8 @@ fn spawn_ai_players(
     let atlas = TextureAtlas::from_grid(handle, Vec2::new(70., 121.), 1, 1, None, None);
     commands.spawn((
         Racer::default(),
-        Angle(PI / 12.0),
-        Velocity(Vec2::new(0.0, 20.0)),
+        physics::Angle(PI / 12.0),
+        physics::Velocity(Vec2::new(0.0, 20.0)),
         SpriteSheetBundle {
             texture_atlas: texture_atlas.add(atlas),
             transform: Transform {
@@ -232,8 +204,8 @@ fn spawn_ai_players(
     let atlas = TextureAtlas::from_grid(handle, Vec2::new(70., 121.), 1, 1, None, None);
     commands.spawn((
         Racer::default(),
-        Angle(PI / 12.0),
-        Velocity(Vec2::new(0.0, 20.0)),
+        physics::Angle(PI / 12.0),
+        physics::Velocity(Vec2::new(0.0, 20.0)),
         SpriteSheetBundle {
             texture_atlas: texture_atlas.add(atlas),
             transform: Transform {
@@ -246,160 +218,10 @@ fn spawn_ai_players(
     ));
 }
 
-fn apply_friction(
-    mut query: Query<(&mut Velocity, &mut Transform)>,
-    time: Res<Time>,
-    guide: Option<Res<mapping::GuidanceField>>,
-) {
-    let delta = time.delta_seconds();
-    for (mut v, t) in query.iter_mut() {
-        v.0 *= 1.0 - (delta * 1.2);
-
-        if let Some(guide) = &guide {
-            let pos = Vec2::new(t.translation.x, t.translation.y);
-            let pixel = guide.get(&pos);
-            if pixel < 140 {
-                let factor = 1.2 + 1.2 * (1.0 - (pixel as f32 / 140.0));
-                v.0 *= 1.0 - (delta * factor);
-            }
-        }
-    }
-}
-
-fn apply_velocity(mut query: Query<(&Velocity, &mut Transform)>, time: Res<Time>) {
-    let delta = time.delta_seconds();
-    for (v, mut t) in query.iter_mut() {
-        t.translation.x += delta * v.0.x;
-        t.translation.y += delta * v.0.y;
-    }
-}
-
-fn same_side(p1: Vec2, p2: Vec2, line: (Vec2, Vec2)) -> bool {
-    let p1 = Vec3::from((p1, 0.0));
-    let p2 = Vec3::from((p2, 0.0));
-    let line = (Vec3::from((line.0, 0.0)), Vec3::from((line.1, 0.0)));
-
-    let cp1 = (line.1 - line.0).cross(p1 - line.0);
-    let cp2 = (line.1 - line.0).cross(p2 - line.0);
-
-    cp1.dot(cp2) >= 0.0
-}
-
-fn point_in_polygon(pt: Vec2, shape: &[Vec2]) -> bool {
-    let n = shape.len();
-    shape
-        .windows(3)
-        .chain(std::iter::once(
-            [shape[n - 2], shape[n - 1], shape[0]].as_slice(),
-        ))
-        .chain(std::iter::once(
-            [shape[n - 1], shape[0], shape[1]].as_slice(),
-        ))
-        .all(|x| same_side(pt, x[0], (x[1], x[2])))
-}
-
-struct CollisionBox {
-    points: [Vec2; 8],
-}
-
-impl CollisionBox {
-    fn from_transform(tf: &Transform, sz: &Vec2) -> Self {
-        let w = sz.x * 0.5;
-        let h = sz.y * 0.5;
-
-        // c is used to round the corners of the box, choosing
-        // 2.5 is a little arbitrary but it gives a good "feel"
-        // for most artwork... and you could handle special cases
-        // by creating the box by hand.
-        let c = w.min(h) / 2.5;
-
-        Self {
-            points: [
-                vec2(c - w, h),
-                vec2(w - c, h),
-                vec2(w, h - c),
-                vec2(w, c - h),
-                vec2(w - c, -h),
-                vec2(c - w, -h),
-                vec2(-w, c - h),
-                vec2(-w, h - c),
-            ]
-            .iter()
-            .map(|v2| {
-                let v3 = Vec3::from((*v2, 0.0));
-                let pt = tf.transform_point(v3);
-                vec2(pt.x, pt.y)
-            })
-            .to_array(),
-        }
-    }
-
-    /// Test whether two rectangles are touching.
-    fn is_touching(&self, other: &CollisionBox) -> bool {
-        other
-            .points
-            .iter()
-            .any(|pt| point_in_polygon(*pt, &self.points))
-            || self
-                .points
-                .iter()
-                .any(|pt| point_in_polygon(*pt, &other.points))
-    }
-
-    fn draw(&self, gizmos: &mut Gizmos) {
-        for w in self.points.windows(2) {
-            gizmos.line_2d(w[0], w[1], Color::BLUE);
-        }
-        gizmos.line_2d(self.points[7], self.points[0], Color::BLUE);
-    }
-}
-
-fn collision_detection(
-    mut query: Query<(&mut Transform, &Handle<TextureAtlas>, &mut Velocity)>,
-    texture_atlases: Res<Assets<TextureAtlas>>,
-    prefs: Res<Preferences>,
-    mut gizmos: Gizmos,
-) {
-    let mut colliders = query.iter_mut().collect::<Vec<_>>();
-    let mut it = colliders.pairs_mut();
-    while let Some((a, b)) = it.next() {
-        let atx = match texture_atlases.get(a.1) {
-            Some(tx) => tx,
-            None => continue,
-        };
-        let btx = match texture_atlases.get(b.1) {
-            Some(tx) => tx,
-            None => continue,
-        };
-
-        let mut abox = CollisionBox::from_transform(&a.0, &atx.size);
-        let mut bbox = CollisionBox::from_transform(&b.0, &btx.size);
-        if prefs.debug_low() {
-            abox.draw(&mut gizmos);
-            bbox.draw(&mut gizmos);
-        }
-
-        if abox.is_touching(&bbox) {
-            std::mem::swap(&mut a.2 .0, &mut b.2 .0);
-
-            let a2 = vec2(a.0.translation.x, a.0.translation.y);
-            let b2 = vec2(b.0.translation.x, b.0.translation.y);
-            let nudge = Vec3::from(((b2 - a2).normalize() * 0.5, 0.0));
-            while abox.is_touching(&bbox) {
-                a.0.translation -= nudge;
-                b.0.translation += nudge;
-
-                abox = CollisionBox::from_transform(&a.0, &atx.size);
-                bbox = CollisionBox::from_transform(&b.0, &btx.size);
-            }
-        }
-    }
-}
-
 fn handle_keyboard(
     mut query: Query<(
-        &mut Angle,
-        &mut Velocity,
+        &mut physics::Angle,
+        &mut physics::Velocity,
         &mut Transform,
         &mut Racer,
         With<Player>,
@@ -436,8 +258,8 @@ fn handle_keyboard(
 
 fn handle_ai_players(
     mut query: Query<(
-        &mut Angle,
-        &mut Velocity,
+        &mut physics::Angle,
+        &mut physics::Velocity,
         &mut Transform,
         &mut Racer,
         Without<Player>,
@@ -508,7 +330,7 @@ fn handle_ai_players(
 }
 
 fn track_player(
-    player: Query<(&Transform, &Velocity, With<Player>)>,
+    player: Query<(&Transform, &physics::Velocity, With<Player>)>,
     mut camera: Query<(&mut Transform, With<Camera>, Without<Player>)>,
 ) {
     let (txp, _, _) = player.single();
diff --git a/src/physics.rs b/src/physics.rs
new file mode 100644
index 0000000..969c385
--- /dev/null
+++ b/src/physics.rs
@@ -0,0 +1,181 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+// Copyright (C) 2023-2024 Daniel Thompson
+
+#![allow(clippy::type_complexity)]
+
+use bevy::{math::vec2, prelude::*};
+use slicetools::*;
+use std::f32::consts::PI;
+
+use crate::{mapping, util::IteratorToArrayExt, Preferences};
+
+#[derive(Component, Debug, Reflect)]
+pub struct Velocity(pub Vec2);
+
+#[derive(Component, Clone, Debug, Reflect)]
+pub struct Angle(pub f32);
+
+impl Angle {
+    pub fn normalize(&mut self) {
+        while self.0 > PI {
+            self.0 -= 2.0 * PI;
+        }
+        while self.0 < -PI {
+            self.0 += 2.0 * PI;
+        }
+    }
+
+    pub fn to_quat(&self) -> Quat {
+        Quat::from_rotation_z(self.0 - PI / 2.0)
+    }
+}
+
+pub fn apply_friction(
+    mut query: Query<(&mut Velocity, &mut Transform)>,
+    time: Res<Time>,
+    guide: Option<Res<mapping::GuidanceField>>,
+) {
+    let delta = time.delta_seconds();
+    for (mut v, t) in query.iter_mut() {
+        v.0 *= 1.0 - (delta * 1.2);
+
+        if let Some(guide) = &guide {
+            let pos = Vec2::new(t.translation.x, t.translation.y);
+            let pixel = guide.get(&pos);
+            if pixel < 140 {
+                let factor = 1.2 + 1.2 * (1.0 - (pixel as f32 / 140.0));
+                v.0 *= 1.0 - (delta * factor);
+            }
+        }
+    }
+}
+
+pub fn apply_velocity(mut query: Query<(&Velocity, &mut Transform)>, time: Res<Time>) {
+    let delta = time.delta_seconds();
+    for (v, mut t) in query.iter_mut() {
+        t.translation.x += delta * v.0.x;
+        t.translation.y += delta * v.0.y;
+    }
+}
+
+fn same_side(p1: Vec2, p2: Vec2, line: (Vec2, Vec2)) -> bool {
+    let p1 = Vec3::from((p1, 0.0));
+    let p2 = Vec3::from((p2, 0.0));
+    let line = (Vec3::from((line.0, 0.0)), Vec3::from((line.1, 0.0)));
+
+    let cp1 = (line.1 - line.0).cross(p1 - line.0);
+    let cp2 = (line.1 - line.0).cross(p2 - line.0);
+
+    cp1.dot(cp2) >= 0.0
+}
+
+fn point_in_polygon(pt: Vec2, shape: &[Vec2]) -> bool {
+    let n = shape.len();
+    shape
+        .windows(3)
+        .chain(std::iter::once(
+            [shape[n - 2], shape[n - 1], shape[0]].as_slice(),
+        ))
+        .chain(std::iter::once(
+            [shape[n - 1], shape[0], shape[1]].as_slice(),
+        ))
+        .all(|x| same_side(pt, x[0], (x[1], x[2])))
+}
+
+pub struct CollisionBox {
+    points: [Vec2; 8],
+}
+
+impl CollisionBox {
+    pub fn from_transform(tf: &Transform, sz: &Vec2) -> Self {
+        let w = sz.x * 0.5;
+        let h = sz.y * 0.5;
+
+        // c is used to round the corners of the box, choosing
+        // 2.5 is a little arbitrary but it gives a good "feel"
+        // for most artwork... and you could handle special cases
+        // by creating the box by hand.
+        let c = w.min(h) / 2.5;
+
+        Self {
+            points: [
+                vec2(c - w, h),
+                vec2(w - c, h),
+                vec2(w, h - c),
+                vec2(w, c - h),
+                vec2(w - c, -h),
+                vec2(c - w, -h),
+                vec2(-w, c - h),
+                vec2(-w, h - c),
+            ]
+            .iter()
+            .map(|v2| {
+                let v3 = Vec3::from((*v2, 0.0));
+                let pt = tf.transform_point(v3);
+                vec2(pt.x, pt.y)
+            })
+            .to_array(),
+        }
+    }
+
+    /// Test whether two rectangles are touching.
+    pub fn is_touching(&self, other: &CollisionBox) -> bool {
+        other
+            .points
+            .iter()
+            .any(|pt| point_in_polygon(*pt, &self.points))
+            || self
+                .points
+                .iter()
+                .any(|pt| point_in_polygon(*pt, &other.points))
+    }
+
+    pub fn draw(&self, gizmos: &mut Gizmos) {
+        for w in self.points.windows(2) {
+            gizmos.line_2d(w[0], w[1], Color::BLUE);
+        }
+        gizmos.line_2d(self.points[7], self.points[0], Color::BLUE);
+    }
+}
+
+pub fn collision_detection(
+    mut query: Query<(&mut Transform, &Handle<TextureAtlas>, &mut Velocity)>,
+    texture_atlases: Res<Assets<TextureAtlas>>,
+    prefs: Res<Preferences>,
+    mut gizmos: Gizmos,
+) {
+    let mut colliders = query.iter_mut().collect::<Vec<_>>();
+    let mut it = colliders.pairs_mut();
+    while let Some((a, b)) = it.next() {
+        let atx = match texture_atlases.get(a.1) {
+            Some(tx) => tx,
+            None => continue,
+        };
+        let btx = match texture_atlases.get(b.1) {
+            Some(tx) => tx,
+            None => continue,
+        };
+
+        let mut abox = CollisionBox::from_transform(&a.0, &atx.size);
+        let mut bbox = CollisionBox::from_transform(&b.0, &btx.size);
+        if prefs.debug_low() {
+            abox.draw(&mut gizmos);
+            bbox.draw(&mut gizmos);
+        }
+
+        if abox.is_touching(&bbox) {
+            std::mem::swap(&mut a.2 .0, &mut b.2 .0);
+
+            let a2 = vec2(a.0.translation.x, a.0.translation.y);
+            let b2 = vec2(b.0.translation.x, b.0.translation.y);
+            let nudge = Vec3::from(((b2 - a2).normalize() * 0.5, 0.0));
+            while abox.is_touching(&bbox) {
+                a.0.translation -= nudge;
+                b.0.translation += nudge;
+
+                abox = CollisionBox::from_transform(&a.0, &atx.size);
+                bbox = CollisionBox::from_transform(&b.0, &btx.size);
+            }
+        }
+    }
+}