mudança no botão

style.css

@@ -81,11 +81,15 @@ body * {
   left: 0;
   transform: translateY(-50%); /* isso é para alinhar */
   top: 50%;
+  animation: slide-back 0.4s;
 }
 
 .light #switch button {
-  right: 0;
-  left: initial;
+  animation: slide-in 0.4s forwards; /*forwards serve para mantar as propriedades do slide-in*/
+}
+
+#switch button.houver {
+  outline: 8px solid var(--highlight-color);
 }
 
 #switch span {
@@ -165,3 +169,21 @@ ul li a:hover {
     --bg-url: url(./assets/bg-desktop-light.jpg);
   }
 }
+
+@keyframes slide-in {
+  from {
+    left: 0;
+  }
+  to {
+    left: 50%;
+  }
+}
+
+@keyframes slide-back {
+  from {
+    left: 50%;
+  }
+  to {
+    left: 0;
+  }
+}