bevy_mod_parallax scaling

change.diff

diff --git a/examples/cyberpunk.rs b/examples/cyberpunk.rs
index 1d27172..45ff7eb 100644
--- a/examples/cyberpunk.rs
+++ b/examples/cyberpunk.rs
@@ -1,9 +1,11 @@
 use bevy::prelude::*;
 use bevy_parallax::{
-    LayerData, LayerSpeed, ParallaxCameraComponent, ParallaxMoveEvent, ParallaxPlugin,
-    ParallaxResource,
+    LayerComponent, LayerData, LayerSpeed, ParallaxCameraComponent, ParallaxMoveEvent,
+    ParallaxPlugin, ParallaxResource,
 };
 
+const INITIAL_SCALE: f32 = 4.5;
+
 fn main() {
     // Define window
     let primary_window = Window {
@@ -23,7 +25,7 @@ fn main() {
                     tile_size: Vec2::new(96.0, 160.0),
                     cols: 1,
                     rows: 1,
-                    scale: 4.5,
+                    scale: INITIAL_SCALE,
                     z: 0.0,
                     ..Default::default()
                 },
@@ -33,7 +35,7 @@ fn main() {
                     tile_size: Vec2::new(144.0, 160.0),
                     cols: 1,
                     rows: 1,
-                    scale: 4.5,
+                    scale: INITIAL_SCALE,
                     z: 1.0,
                     ..Default::default()
                 },
@@ -43,7 +45,7 @@ fn main() {
                     tile_size: Vec2::new(272.0, 160.0),
                     cols: 1,
                     rows: 1,
-                    scale: 4.5,
+                    scale: INITIAL_SCALE,
                     z: 2.0,
                     ..Default::default()
                 },
@@ -61,7 +63,9 @@ fn main() {
         )
         .add_plugin(ParallaxPlugin)
         .add_startup_system(initialize_camera_system)
+        .add_startup_system(setup_player)
         .add_system(move_camera_system)
+        .add_system(zoom)
         .run();
 }
 
@@ -72,6 +76,40 @@ pub fn initialize_camera_system(mut commands: Commands) {
         .insert(ParallaxCameraComponent);
 }
 
+fn setup_player(mut commands: Commands) {
+    commands.spawn(SpriteBundle {
+        sprite: Sprite {
+            custom_size: Some(Vec2::splat(50.)),
+            color: Color::RED,
+            ..default()
+        },
+        transform: Transform::from_xyz(0., 0., 100.),
+        ..default()
+    });
+}
+
+fn zoom(
+    input: Res<Input<KeyCode>>,
+    mut query_camera: Query<&mut OrthographicProjection>,
+    mut container: Query<&mut Transform, With<LayerComponent>>,
+) {
+    let mut proj = query_camera.single_mut();
+
+    if input.pressed(KeyCode::Minus) {
+        proj.scale += 0.2;
+    }
+
+    if input.pressed(KeyCode::Equals) {
+        proj.scale -= 0.2;
+    }
+
+    proj.scale = proj.scale.clamp(0.2, 5.);
+
+    for mut transform in container.iter_mut() {
+        transform.scale = Vec2::splat(INITIAL_SCALE * proj.scale).extend(1.);
+    }
+}
+
 // Send a ParallaxMoveEvent with the desired camera movement speed
 pub fn move_camera_system(
     keyboard_input: Res<Input<KeyCode>>,