completed first steps

src/main.rs

@@ -2,16 +2,10 @@ use bevy::prelude::*;
 
 fn main() {
     App::new()
-        .add_plugins(DefaultPlugins)
-        .add_systems(Startup, add_people)
-        .add_systems(Update, (hello_world, (update_people, greet_people).chain()))
+        .add_plugins((DefaultPlugins, HelloPlugin))
         .run();
 }
 
-fn hello_world() {
-    println!("hi!");
-}
-
 #[derive(Component)]
 struct Person;
 
@@ -24,9 +18,18 @@ fn add_people(mut commands: Commands) {
     commands.spawn((Person, Name("Marie Skłodowska".to_string())));
 }
 
-fn greet_people(query: Query<&Name, With<Person>>) {
-    for name in &query {
-        println!("hello {}!", name.0);
+#[derive(Resource)]
+struct GreetTimer(Timer);
+
+fn greet_people(
+    time: Res<Time>,
+    mut timer: ResMut<GreetTimer>,
+    query: Query<&Name, With<Person>>
+) {
+    if timer.0.tick(time.delta()).just_finished() {
+        for name in &query {
+            println!("hello {}!", name.0);
+       }
     }
 }
 
@@ -38,3 +41,13 @@ fn update_people(mut query: Query<&mut Name, With<Person>>) {
         }
     }
 }
+
+pub struct HelloPlugin;
+
+impl Plugin for HelloPlugin {
+    fn build(&self, app: &mut App) {
+        app.insert_resource(GreetTimer(Timer::from_seconds(2.0, TimerMode::Repeating)))
+            .add_systems(Startup,add_people)
+            .add_systems(Update, (update_people, greet_people).chain());
+    }
+}