small ad for the c3nav android app

src/c3nav/site/static/site/css/c3nav.scss

@@ -1075,6 +1075,34 @@ ul.messages li.alert-danger {
     background-color:#FFEEEE;
 }
 
+.app-ads {
+    position:absolute;
+    z-index: 10;
+    bottom:0;
+    right:0;
+    left:0;
+    padding:0;
+    text-align: center;
+    display:none;
+}
+.app-ads div {
+    background-color: #ffffff;
+    -webkit-box-shadow: 1px 1px 3px rgba(0, 0, 0, 0.2);
+            box-shadow: 1px 1px 3px rgba(0, 0, 0, 0.2);
+    border-radius: 2px;
+    overflow: hidden;
+    display: inline-block;
+    margin: 0 10px 25px;
+    padding: 10px;
+    vertical-align: middle;
+}
+.app-ads .close {
+    float: right;
+    color: inherit;
+    line-height: 16px;
+    margin-left: 10px;
+}
+
 #messages {
     z-index: 5;
     position: absolute;

src/c3nav/site/static/site/js/c3nav.js

@@ -50,6 +50,16 @@ c3nav = {
             );
         });
 
+        if ((!localStorage || !localStorage.getItem('hideAppAds')) && navigator.userAgent.toLowerCase().indexOf("android") > -1) {
+            $('.app-ads').show();
+            $('.app-ads .close').click(function() {
+                localStorage.setItem('hideAppAds', true);
+                $('.app-ads').remove();
+            });
+        } else {
+            $('.app-ads').remove();
+        }
+
         if (window.mobileclient) {
             var $body = $('body');
             $body.addClass('mobileclient');

src/c3nav/site/templates/site/map.html

@@ -144,6 +144,12 @@
                     </section>
                 </div>
             </section>
+            <div class="app-ads">
+                <div id="android-app-ad">
+                    <a href="#" class="close"><i class="material-icons">close</i></a>
+                    <a href="https://play.google.com/store/apps/details?id=de.c3nav.droid">{% trans 'Get the c3nav Android app!' %}</a>
+                </div>
+            </div>
         {% else %}
             <a id="embed-logo" class="embed-link" target="_blank">{% if header_logo %}<img src="{% static header_logo %}">{% else %}<span>c3nav</span>{% endif %}</a>
             <a id="embed-open" class="embed-link" target="_blank">{% trans 'open in c3nav' %}</a>