Add chunk constructor

src/falling_sand/mod.rs

@@ -46,14 +46,7 @@ fn setup(mut commands: Commands, mut images: ResMut<Assets<Image>>) {
 
     let image_handle = images.add(image);
 
-    commands
+    commands.spawn(Chunk::new(256, 256)).insert(SpriteBundle {
-        .spawn(Chunk {
-            width: 256,
-            height: 256,
-            cells: vec![Elements::Air; 256 * 256],
-            dirty_rect: DirtyRect::default(),
-        })
-        .insert(SpriteBundle {
         sprite: Sprite {
             flip_y: true,
             ..default()
@@ -73,6 +66,17 @@ pub struct Chunk {
     dirty_rect: DirtyRect,
 }
 
+impl Chunk {
+    pub fn new(width: usize, height: usize) -> Self {
+        Self {
+            width,
+            height,
+            cells: vec![Elements::Air; width * height],
+            dirty_rect: DirtyRect::default(),
+        }
+    }
+}
+
 pub fn place_sand_system(mut chunk: Query<&mut Chunk>) {
     // We know for now there's only one chunk
     let chunk = chunk.get_single_mut();