pseudo-states appear to be working + variables only exist within the scope where they are created

src/App/App.css

@@ -1,28 +1,3 @@
-/* .layoutVertical {
-  display: flex;
-  flex-direction: column;
-  width: 100%;
-  height: 100vh;
-}
-.panel {
-  height: 1.5rem;
-  background-color: lightgrey;
-}
-.layout {
-  display: flex;
-  width: 100%;
-  height: calc(100vh - 1.5rem);
-}
-
-.sidebar {
-  flex: 0 0 content;
-  padding-right: 4px;
-}
-.content {
-  flex: 1 1 auto;
-  overflow: auto;
-} */
-
 details {
   padding-left: 20;
   /* margin-left: 30; */
@@ -68,4 +43,10 @@ summary {
 }
 .toolbar > input {
   height: 20px;
+}
+
+button.active {
+  border: solid blue 2px;
+  background-color: rgba(0,0,255,0.2);
+  color: black;
 }