use bevy states

despawn plugin
buiding plugin

game/shared/src/despawn.rs

@@ -0,0 +1,47 @@
+use crate::states::GameState;
+use bevy::prelude::*;
+
+pub struct DespawnPuglin;
+
+#[derive(Component)]
+pub struct DespawnAt(f32);
+
+#[derive(Component)]
+pub struct DespawnAfter(Timer);
+
+#[derive(Component)]
+pub struct Despawn;
+
+impl Plugin for DespawnPuglin {
+	fn build(&self, app: &mut App) {
+		app.add_systems(PostUpdate, despawn_at);
+		app.add_systems(
+			PreUpdate,
+			(despawn, despawn_after).run_if(not(in_state(GameState::Paused))),
+		);
+	}
+}
+
+fn despawn_at(mut commands: Commands, time: Res<Time>, entities: Query<(Entity, &DespawnAt), Without<DespawnAfter>>) {
+	for (entity, at) in entities.iter() {
+		let d = at.0 - time.elapsed_seconds();
+		commands
+			.entity(entity)
+			.insert(DespawnAfter(Timer::from_seconds(d, TimerMode::Once)));
+	}
+}
+
+fn despawn_after(mut commands: Commands, mut entities: Query<(&mut DespawnAfter, Entity)>, time: Res<Time>) {
+	for (mut after, entity) in &mut entities.iter_mut() {
+		after.0.tick(time.delta());
+		if after.0.finished() {
+			commands.entity(entity).despawn();
+		}
+	}
+}
+
+fn despawn(mut commands: Commands, entities: Query<Entity, With<Despawn>>) {
+	for entity in entities.iter() {
+		commands.entity(entity).despawn();
+	}
+}