follow getting started guide

src/main.rs

@@ -2,8 +2,8 @@ use bevy::prelude::*;
 
 fn main() {
     App::new()
-        .add_systems(Startup, add_people)
-        .add_systems(Update, hello_world)
+        .add_plugins(DefaultPlugins)
+        .add_plugins(HelloPlugin)
         .run();
 }
 //region first app
@@ -24,5 +24,31 @@ fn add_people(mut commands: Commands) {
     commands.spawn((Person, Name("Renzo Hume".to_string())));
     commands.spawn((Person, Name("Zayna Nieves".to_string())));
 }
+#[derive(Component)]
+struct GreetTimer(Timer);
+//endregion
+//region query
+fn greet_people(query: Query<&Name, With<Person>>) {
+    for name in &query {
+        println!("hello {}!", name.0);
+    }
+}
+fn update_people(mut query: Query<&mut Name, With<Person>>) {
+    for mut name in &mut query {
+        if name.0 == "Elaina Proctor" {
+            name.0 = "Elaina Hume".to_string();
+            break;
+        }
+    }
+}
+//endregion
+//region Plugin
+pub struct HelloPlugin;
+impl Plugin for HelloPlugin {
+    fn build(&self, app: &mut App) {
+        app.add_systems(Startup, add_people)
+            .add_systems(Update, (hello_world, (update_people, greet_people).chain()));
+    }
+}
 //endregion
 //endregion