Fix nav overflow

sass/components/modal.sass

@@ -75,7 +75,7 @@
   justify-content: center
   overflow: hidden
   position: fixed
-  z-index: 1986
+  z-index: 20
   // Modifiers
   &.is-active
     display: flex

sass/components/nav.sass

@@ -62,11 +62,15 @@ a.nav-item
 
 .nav-left,
 .nav-right
+  +overflow-touch
   align-items: stretch
   display: flex
-  flex-basis: 0
   flex-grow: 1
   flex-shrink: 0
+  max-width: 100%
+  overflow: auto
+  +widescreen
+    flex-basis: 0
 
 .nav-left
   justify-content: flex-start
@@ -107,10 +111,10 @@ a.nav-item
   align-items: stretch
   background-color: $white
   display: flex
-  min-height: $nav-height
+  height: $nav-height
   position: relative
   text-align: center
-  z-index: 2
+  z-index: 10
   & > .container
     align-items: stretch
     display: flex

sass/components/tabs.sass

@@ -1,5 +1,6 @@
 .tabs
   +block
+  +overflow-touch
   +unselectable
   align-items: stretch
   display: flex