add some basic camera movement

src/main.rs

@@ -1,21 +1,25 @@
 use bevy::prelude::*;
 
 #[derive(Component)]
-struct Rotator;
+struct Mover;
 
 fn main() {
     App::new()
+        .insert_resource(Movement { dx: 0.0, dy: 0.0 })
         .add_plugins(DefaultPlugins)
         .add_systems(Startup, setup)
-        .add_systems(Update, rotate)
+        .add_systems(Update, (input, decay, movement))
         .run();
 }
 
 fn setup(mut commands: Commands, asset_server: Res<AssetServer>) {
-    commands.spawn(Camera3dBundle {
-        transform: Transform::from_xyz(0.0, 12.0, 18.0).looking_at(Vec3::ZERO, Vec3::Y),
-        ..default()
-    });
+    commands.spawn((
+        Camera3dBundle {
+            transform: Transform::from_xyz(0.0, 12.0, 18.0).looking_at(Vec3::ZERO, Vec3::Y),
+            ..default()
+        },
+        Mover,
+    ));
 
     commands.spawn(PointLightBundle {
         point_light: PointLight {
@@ -51,8 +55,59 @@ fn setup(mut commands: Commands, asset_server: Res<AssetServer>) {
     }
 }
 
-fn rotate(mut query: Query<&mut Transform, With<Rotator>>, time: Res<Time>) {
+#[derive(Debug, Resource)]
+struct Movement {
+    dx: f32,
+    dy: f32,
+}
+
+impl Default for Movement {
+    fn default() -> Movement {
+        Movement { dx: 0.0, dy: 0.0 }
+    }
+}
+
+const ACCEL: f32 = 0.002;
+
+fn input(keyboard: Res<ButtonInput<KeyCode>>, mut mvmt: ResMut<Movement>) {
+    if keyboard.pressed(KeyCode::ArrowUp) {
+        mvmt.dy = (mvmt.dy - ACCEL).clamp(-0.5, 0.5);
+    }
+    if keyboard.pressed(KeyCode::ArrowDown) {
+        mvmt.dy = (mvmt.dy + ACCEL).clamp(-0.5, 0.5);
+    }
+    if keyboard.pressed(KeyCode::ArrowLeft) {
+        mvmt.dx = (mvmt.dx - ACCEL).clamp(-0.5, 0.5);
+    }
+    if keyboard.pressed(KeyCode::ArrowRight) {
+        mvmt.dx = (mvmt.dx + ACCEL).clamp(-0.5, 0.5);
+    }
+}
+
+fn decay(mut mvmt: ResMut<Movement>) {
+    if mvmt.dx.abs() < 0.001 {
+        mvmt.dx = 0.0;
+    } else {
+        mvmt.dx *= 0.90;
+    }
+
+    if mvmt.dy.abs() < 0.001 {
+        mvmt.dy = 0.0;
+    } else {
+        mvmt.dy *= 0.90;
+    }
+}
+
+fn movement(mut query: Query<&mut Transform, With<Mover>>, mvmt: Res<Movement>, time: Res<Time>) {
+    if time.delta_seconds() == 0.0 {
+        return;
+    }
+
     for mut transform in &mut query {
-        transform.rotate_y(time.delta_seconds() / 2.);
+        transform.translation += Vec3::new(
+            mvmt.dx / time.delta_seconds(),
+            0.0,
+            mvmt.dy / time.delta_seconds(),
+        );
     }
 }