intro with basic animation

assets/martian.tweak.toml

@@ -30,6 +30,8 @@ Background 2D art by NASA: LINK HERE
 """
 
 [intro]
+# Higher rate is slower typing speed. Integers only!
+rate = 5
 text = """
 At the intersection of humanity's wildest imaginations and the infinite of the cosmos, the lines between possible and real fall apart like dissolving paper.
 

src/intro.rs

@@ -1,3 +1,5 @@
+use bevy::core::FrameCount;
+
 use crate::prelude::*;
 
 pub(crate) struct IntroPlugin;
@@ -8,11 +10,16 @@ impl Plugin for IntroPlugin {
             OnExit(GameState::Loading),
             init_intro_text.run_if(resource_exists::<tweak::GameTweaks>()),
         )
+        .init_resource::<IntroProgress>()
         .add_systems(OnEnter(GameState::Intro), activate::<Intro>)
         .add_systems(OnExit(GameState::Intro), deactivate::<Intro>)
-		.add_systems(Update, play_intro
-			.run_if(in_state(GameState::<Intro>()))
+        .add_systems(Update, manage_intro_progress
+            .run_if(in_state(GameState::Intro))
             .run_if(not(resource_exists::<IntroPlayed>()))
+        )
+		.add_systems(Update, play_intro
+            .run_if(in_state(GameState::Intro))
+            .run_if(resource_changed::<IntroProgress>())
         )
         // Continue to play state if the intro is done playing out
         .add_systems(
@@ -30,6 +37,9 @@ struct Intro;
 #[derive(Debug, Resource)]
 struct IntroPlayed;
 
+#[derive(Debug, Resource, Default)]
+struct IntroProgress(usize);
+
 // Draw the intro text (invisible) on startup
 // Requires the Tweakfile to be loaded
 fn init_intro_text(
@@ -67,7 +77,7 @@ fn init_intro_text(
                     value: c.to_string(),
                     style: TextStyle {
                         font_size: 16.0,
-                        color: Color::WHITE,
+                        color: Color::WHITE.with_a(0.0),
                         ..default()
                     },
                 }))
@@ -76,14 +86,65 @@ fn init_intro_text(
         });
 }
 
+fn manage_intro_progress(
+    keys: Res<Input<KeyCode>>,
+    mut start: Local<u32>,
+	mut progress: ResMut<IntroProgress>,
+    framecount: Res<FrameCount>,
+	mut commands: Commands,
+    tweaks_file: Res<tweak::GameTweaks>,
+    tweaks: Res<Assets<tweak::Tweaks>>,
+) {
+    // If this is the first run, initialize the starting point
+    if *start == 0 {
+        *start = framecount.0;
+    }
+
+    // If the user hits 'return' set this to the end of the animation
+    if keys.just_pressed(KeyCode::Return) {
+        progress.0 = usize::MAX;
+	    commands.insert_resource(IntroPlayed);
+    // Otherwise progress by N characters (1)
+    } else {
+        let tweak = tweaks
+            .get(tweaks_file.handle.clone())
+            .expect("Load tweaks");
+        let rate = tweak.get::<u32>("intro_rate").expect("[intro] rate = #");
+
+        progress.0 = ((framecount.0 - *start) / rate) as usize;
+    }
+}
+
 // Upon entering the Intro state, start the intro "animation"
 fn play_intro(
-	mut text: Query<&mut Text, With<Intro>>,
-	progress: Local<f32>,
+	mut text: Query<(&mut Text, &mut Visibility), With<Intro>>,
+    progress: Res<IntroProgress>,
 	mut commands: Commands,
 ) {
-	todo!("Play the intro animation, typing each character one at a time...");
+    // Iterate over all (one) text
+    text.iter_mut().for_each(|(mut t, mut v)| {
+        // If this is the first frame of the animation, make the object visibility
+        if progress.0 == 0 {
+            *v = Visibility::Inherited;
+        }
+
+        // Iterate over all characters in the intro text
+        t.sections
+            .iter_mut()
+            .enumerate()
+            // Only operate on sections up to this point
+            .filter_map(|(i, s)| {
+                (i <= progress.0).then_some(s)
+            })
+            // Set the alpha to 1.0 making it visible
+            .for_each(|s| {
+                s.style.color.set_a(1.0);
+            });
+
+        if t.sections.iter().all(|s| s.style.color.a() == 1.0) {
             commands.insert_resource(IntroPlayed);
+        }
+    });
 }
 // Intro animation reveals one character every nth frame