Music player in the sound settings: pick any calm track or automatic

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/main.rs

@@ -481,7 +481,8 @@ impl MusicDirector {
         t
     }
 
-    fn update(&mut self, g: &Game, title: bool, cam: (f32, f32)) {
+    // `chosen`: a track picked in the music player; it replaces the calm music
+    fn update(&mut self, g: &Game, title: bool, cam: (f32, f32), chosen: Option<usize>) {
         use audio::Category as C;
         let alive = |f: &dyn Fn(&game::Ent) -> bool| g.ents.iter().any(|e| e.alive && f(e));
         let near_room = |k: map::Kind| {
@@ -535,8 +536,19 @@ impl MusicDirector {
             C::Build | C::Torture | C::Temple if above => C::Surface,
             w => w,
         };
+        let calm = matches!(want, C::Build | C::Title | C::Surface | C::Torture | C::Temple);
+        if let (true, Some(t)) = (calm, chosen) {
+            if audio::current_track() != Some(t) {
+                let fade = if self.current.map_or(false, |c| matches!(c, C::Victory | C::Defeat)) { 1.0 } else { 2.5 };
+                audio::play_music(t, fade);
+            }
+            self.current = Some(want);
+            return;
+        }
         let rotate = matches!(want, C::Build | C::Title | C::Surface) && self.current == Some(want) && audio::music_loops() >= 2;
-        if self.current != Some(want) || rotate || audio::current_track().is_none() {
+        // after the chosen track was let go, the director picks again
+        let foreign = chosen.is_none() && audio::current_track().map_or(false, |t| crate::tracks::TRACKS.get(t).map_or(false, |x| x.1 != want)) && calm && self.current == Some(want);
+        if self.current != Some(want) || rotate || foreign || audio::current_track().is_none() {
             let before = self.current;
             self.current = Some(want);
             let t = self.pick(want);
@@ -2005,7 +2017,7 @@ app.pending_briefing = briefing_of(&campaign, i);
                     | Some(Page::Match { from_title: true })
                     | Some(Page::Achievements { from_title: true })
             );
-        music.update(&app.game, on_title, (app.cam.rx, app.cam.rz));
+        music.update(&app.game, on_title, (app.cam.rx, app.cam.rz), audio::track_by_id(&app.settings.music_track));
         // ---------------- achievements: count the game, unlock, store and share the profile
         {
             let ctx = achievements::Context { coop: app.coop, editor_test: app.editor_testing };