Wire the 'Start' button to a state changer

client/src/ui.rs

@@ -5,6 +5,8 @@ use bevy::{
     prelude::*,
 };
 
+use crate::GameState;
+
 pub const BTN_BORDER_COLOR: Color = Color::WHITE;
 pub const BTN_BG_COLOR: Color = Color::BLACK;
 pub const BTN_BG_SELECTED: Color = bevy::prelude::Color::Srgba(DARK_GRAY);
@@ -29,9 +31,11 @@ pub fn spawn_main_menu(mut commands: Commands) {
                 TextShadow::default(),
             ));
             let mut start_button = cmds.spawn(button_bundle("Start game"));
-            start_button.observe(|_trigger: On<Pointer<Click>>| {
-                info!("The start button was pressed.");
-            });
+            start_button.observe(
+                |_trigger: On<Pointer<Click>>, mut game_state: ResMut<NextState<GameState>>| {
+                    game_state.set(GameState::Playing);
+                },
+            );
             let mut quit_button = cmds.spawn(button_bundle("Quit Game"));
             quit_button.observe(
                 |_trigger: On<Pointer<Click>>, mut messages: MessageWriter<AppExit>| {