add button to turn volume on and off

script/audio.js

@@ -176,6 +176,26 @@ var AudioEngine = {
                 });
             });
         }
+    },
+    mute: function () {
+        AudioEngine.master.gain.linearRampToValueAtTime(
+            0.0,
+            AudioEngine.audioContext.currentTime + AudioEngine.FADE_TIME
+        );
+    },
+    setVolume: function (volume) {
+        if (!AudioEngine.master) return; // master may not be ready yet
+        if (!volume) {
+            volume = 1.0;
+        }
+        AudioEngine.master.gain.setValueAtTime(
+            AudioEngine.master.gain.value,
+            AudioEngine.audioContext.currentTime
+        );
+        AudioEngine.master.gain.linearRampToValueAtTime(
+            volume,
+            AudioEngine.audioContext.currentTime + AudioEngine.FADE_TIME / 2
+        );
     }
 };
 

script/engine.js

@@ -133,6 +133,12 @@
 				});
 			}
 
+			$('<span>')
+				.addClass('volume menuBtn')
+				.text(_('sound off.'))
+				.click(Engine.toggleVolume)
+				.appendTo(menu);
+
 			$('<span>')
 				.addClass('appStore menuBtn')
 				.text(_('get the app.'))
@@ -215,6 +221,10 @@
 				Ship.init();
 			}
 
+			if(!$SM.get('config.soundOn')){
+				Engine.toggleVolume();
+			}
+
 			if($SM.get('config.lightsOff', true)){
 				Engine.turnLightsOff();
 			}
@@ -782,6 +792,18 @@
 			}
 		},
 
+		toggleVolume: function() {
+			if ($SM.get('config.soundOn')) {
+				$('.volume').text(_('sound on.'));
+				$SM.set('config.soundOn', false);
+				AudioEngine.mute();
+			} else {
+				$('.volume').text(_('sound off.'));
+				$SM.set('config.soundOn', true);
+				AudioEngine.setVolume(1.0);
+			}
+		},
+
 		setInterval: function(callback, interval, skipDouble){
 			if( Engine.options.doubleTime && !skipDouble ){
 				Engine.log('Double time, cutting interval in half');