Update style.css

style.css

-a{font-size: 20px
-spacing: 20px}
+h1
+{ color: blue;}
+button
+{color: greenyellow;
+border-spacing: 20px;
+size: 4000000px;
+
+}
+
+li {
+  display: inline;
+  border-right: 1px solid #bbb;
+  float:left;
+  border-top-right-radius: 1000%;
+  border-bottom-right-radius: 1000%;
+}
+
+li:last-child {
+  color: red;
+background-color: red;
+  border-right: none;
+  border-top-left-radius: 1000%;
+  border-bottom-left-radius: 1000%;
+}
+ul {
+  list-style-type: none;
+  margin: 0;
+  padding: 0;
+  overflow: hidden;
+  background-color: #333;
+}
+
+
+li a {
+  display: block;
+  color: white;
+  text-align: center;
+  padding: 14px 16px;
+  text-decoration: none;
+}
+
+
+li a:hover {
+  border-bottom-right-radius: 1000%;
+  border-top-right-radius: 1000%;
+  border-top-left-radius: -1000%;
+  border-radius: 1000;
+  background-color: #111;
+}
+
+li a:hover:last-child {
+  border-bottom-right-radius: 1000%;
+  border-top-right-radius: 1000%;
+  border-top-left-radius: 1000%;
+  border-radius: 50%;
+
+  background-color: #111;
+}