menu-controls allow unselecting / going back, remove unnoticable animations for perf

src/components/intro-song.js

@@ -1,9 +1,33 @@
 AFRAME.registerComponent('intro-song', {
-  multiple: true,
+  schema: {
+    isPlaying: {default: true}
+  },
+
+  init: function () {
+    this.analyserEl = document.getElementById('audioAnalyser');
+    this.audio = document.getElementById('introSong');
+  },
+
+  update: function (oldData) {
+    const audio = this.audio;
+
+    if (!this.el.sceneEl.isPlaying) { return; }
+
+    if (!oldData.isPlaying && this.data.isPlaying) {
+      setTimeout(() => {
+        // TODO: Fade in volume.
+        this.analyserEl.setAttribute('audioanalyser', 'src', audio);
+        audio.play();
+      }, 1000);
+    }
+
+    if (oldData.isPlaying && !this.data.isPlaying) {
+      audio.pause();
+    }
+  },
 
   play: function () {
-    const audio = document.getElementById('introSong');
-    audio.volume = 0.5;
-    audio.play();
+    this.audio.volume = 0.5;
+    this.audio.play();
   }
 });

src/components/menu-controls.js

@@ -111,7 +111,9 @@ AFRAME.registerComponent('menu-controls', {
 
   unselect: function () {
     if (!this.data.enabled) { return; }
-    this.el.sceneEl.emit('menuunselect', null, false);
+    if (this.data.selectedChallengeId) {
+      this.el.sceneEl.emit('menuchallengeunselect', null, false);
+    }
   },
 
   hoverResult: function (i) {

src/components/song-preview.js

@@ -9,6 +9,7 @@ AFRAME.registerComponent('song-preview-system', {
   },
 
   init: function () {
+    this.analyserEl = document.getElementById('audioAnalyser');
     this.audio = null;
     this.audioStore = {};
     this.preloadedAudioIds = [];
@@ -162,8 +163,7 @@ AFRAME.registerComponent('song-preview-system', {
   },
 
   updateAnalyser: function () {
-    document.getElementById('audioAnalyser').setAttribute('audioanalyser', 'src', this.audio);
-    document.getElementById('introSong').pause();
+    this.analyserEl.setAttribute('audioanalyser', 'src', this.audio);
   },
 
   /**