Add mobile classes

static/css/app.css

@@ -44,18 +44,6 @@ body {
     padding: 0px 5px;
 }
 
-.mgn-btm-10px {
-    margin-bottom: 10px;
-}
-
-.mgn-top-8px {
-    margin-top: 8px;
-}
-
-.black-text {
-    color: black;
-}
-
 .footer {
     margin-top: 10em;
     text-align: center;
@@ -69,4 +57,12 @@ body {
 .footer {
     margin-top: 10em;
     text-align: center;
+}
+
+.mobile-app-show {
+    visibility: hidden;
+}
+
+.mobile-app-display {
+    display: none;
 }