diff --git a/style.css b/style.css
index be77ea1..3f77f97 100644
--- a/style.css
+++ b/style.css
@@ -68,6 +68,11 @@
   --border-field: inset -1px -1px var(--button-highlight),
     inset 1px 1px var(--button-shadow), inset -2px -2px var(--button-face),
     inset 2px 2px var(--window-frame);
+
+  --border-tab: inset -1px 0 var(--window-frame),
+    inset 1px 1px var(--button-highlight),
+    inset -2px 0 var(--button-shadow),
+    inset 2px 2px var(--button-face)
 }
 
 @font-face {
@@ -732,3 +737,45 @@ summary:focus {
   width: 16px;
   background-image: svg-load("./icon/button-right.svg");
 }
+
+menu.tabs {
+  position: relative;
+  margin: 0 0 -2px 0;
+  text-indent: 0;
+  list-style-type: none;
+  display: flex;
+  padding-left: 3px;
+}
+
+menu.tabs li {
+  border-top-left-radius: 3px;
+  border-top-right-radius: 3px;
+  box-shadow: var(--border-tab);
+  z-index: 1;
+}
+menu.tabs > li.active {
+  padding-bottom: 2px;
+  margin-top: -2px;
+  background-color: var(--surface);
+  position: relative;
+  z-index: 8;
+  margin-left: -3px;
+}
+
+menu.tabs > li > a {
+  display: block;
+  color: #222;
+  margin: 6px;
+  text-decoration: none;
+}
+menu.tabs > li.active > a:focus {
+  outline: none;
+}
+menu.tabs > li > a:focus {
+  outline: 1px dotted #222;
+}
+
+menu.tabs.justified > li {
+  flex-grow: 1;
+  text-align: center;
+}