header nav: switch to dropdown menus

frontend/src/main.sass

@@ -1,13 +1,11 @@
 header
   width: 100vw
-  min-height: 3em
 
   background-color: green
   color: white
   font-weight: 600
   font-size: 1.2em
   line-height: 1.5em
-  white-space: nowrap
 
   a
     color: white
@@ -17,25 +15,30 @@ header
       text-decoration: none
 
   // parent menu
-  & > nav ul
+  & > nav > ul
     display: inline
     list-style-type: none
     margin: 0
     padding: 0
-    overflow: hidden
 
     // menu items
     & > li
-      display: inline
+      display: inline-block
       padding: 4px 20px
+      white-space: nowrap
 
-      // submenus
-      & > ul
-        display: none
-        position: absolute
-        width: 100vw
-        z-index: 1
       &:hover
         background-color: red
         & > ul
           display: block
+
+      // submenus
+      & > ul
+        background-color: black
+        display: none
+        position: absolute
+        z-index: 1
+        list-style-type: none
+
+        & > li:hover
+          background-color: red