Added mobile layout

_sass/partials/_helpers.scss

@@ -5,3 +5,12 @@
     clear: both;
    }
 }
+
+.visually-hidden {
+  position:absolute;
+  left:-10000px;
+  top:auto;
+  width:1px;
+  height:1px;
+  overflow:hidden;
+}

_sass/partials/_media-queries.scss

@@ -0,0 +1,43 @@
+/*============================================================================
+  Media queries
+==============================================================================*/
+
+$phone-width: 321px;
+$tablet-width: 768px;
+$desktop-width: 1024px;
+
+@mixin phone {
+  @media (max-width: #{$phone-width}) {
+    @content;
+  }
+}
+
+@mixin phone-and-up {
+  @media (min-width: #{$phone-width}) {
+    @content;
+  }
+}
+
+@mixin phone-to-tablet {
+  @media (min-width: #{$phone-width}) and (max-width: #{$tablet-width - 1px}) {
+    @content;
+  }
+}
+
+@mixin tablet {
+  @media (min-width: #{$tablet-width}) and (max-width: #{$desktop-width - 1px}) {
+    @content;
+  }
+}
+
+@mixin tablet-and-up {
+  @media (min-width: #{$tablet-width}) {
+    @content;
+  }
+}
+
+@mixin desktop {
+  @media (min-width: #{$desktop-width}) {
+    @content;
+  }
+}