Very roughly using the spotlight valid move indicators

src/display3d.rs

@@ -1,5 +1,5 @@
 use crate::{
-    game::{Board, BoardIndex, Piece, Side},
+    game::{Board, BoardIndex, Piece, Side, BoardComponent},
     prelude::*,
 };
 use bevy::{
@@ -40,6 +40,9 @@ impl Plugin for Display3dPlugin {
                     switch_sides
                         .run_if(in_state(GameState::Play))
                         .run_if(state_changed::<game::TurnState>()),
+                    create_valid_move_entity.run_if(any_component_added::<game::Selected>),
+                    remove_valid_move_entity.run_if(any_component_removed::<game::Selected>()),
+                    set_valid_move_model.run_if(any_component_added::<game::ValidMove>),
                 ),
             )
             .add_systems(
@@ -562,6 +565,59 @@ fn moves_gizmo(
     });
 }
 
+/// Spawn 3d "Valid move" indicators when a piece is selected
+/// Another system registers these new entities and associates the correct models and plays animations.
+fn create_valid_move_entity(
+    events: Query<&BoardIndex, (With<game::Piece>, Added<game::Selected>, With<Display3d>)>,
+    board: Res<Board>,
+    root: Query<Entity, With<game::BoardComponent>>,
+    mut commands: Commands,
+) {
+    events.iter().for_each(|idx| {
+        if let Ok(board_entity) = root.get_single() {
+            board
+                .valid_moves(*idx)
+                .iter()
+                .map(|i| Transform::from_translation(board_translation(i)))
+                .for_each(|t| {
+                    commands.entity(board_entity).with_children(|parent| {
+                        parent.spawn((Display3d, game::ValidMove, SceneBundle { ..default() })).insert(t);
+                    });
+                });
+        }
+    });
+}
+
+fn set_valid_move_model(
+    mut events: Query<&mut Handle<Scene>, (With<Display3d>, Added<game::ValidMove>)>,
+    gltfs: Res<Assets<Gltf>>,
+    assets_map: Res<AssetsMap>,
+) {
+    if let Some(gltf) = gltfs.get(&assets_map.models) {
+        events.iter_mut().for_each(|mut handle| *handle = gltf.named_scenes.get("Valid Move Spot").unwrap().clone())
+    }
+}
+
+fn play_valid_move_animation(
+    players: Query<&AnimationPlayer>,
+) {
+    todo!();
+}
+
+// TODO: Move this to game.rs
+/// Remove "Valid Move" indicators when a piece is de-selected
+fn remove_valid_move_entity(
+    mut events: RemovedComponents<game::Selected>,
+    valid_moves: Query<Entity, With<game::ValidMove>>,
+    mut commands: Commands,
+) {
+    events.iter().for_each(|_| {
+        valid_moves.iter().for_each(|entity| {
+            commands.entity(entity).despawn_recursive();
+        });
+    });
+}
+
 fn pick_up(
     mut events: Query<
         (Entity, &game::Piece),

src/game.rs

@@ -80,6 +80,9 @@ pub(crate) fn tiles() -> impl Iterator<Item = (BoardIndex, Tile)> {
 #[derive(Debug, Component)]
 pub(crate) struct BoardComponent;
 
+#[derive(Debug, Component)]
+pub(crate) struct ValidMove;
+
 #[derive(Debug, Component)]
 pub(crate) struct Captured;