add vue transition

src/components/HelloWorld.vue

@@ -111,6 +111,7 @@ const showSources = ref(true);
 <template>
   <div class="box" @click="showSources = !showSources">
     <p class="average">1 BTC = <span class="nobr">{{ format(average) }} USD</span></p>
+    <Transition>
       <div v-show="showSources">
         <p>Data Sources:</p>
         <ul>
@@ -120,10 +121,21 @@ const showSources = ref(true);
         </ul>
         <p>Standard Deviation: {{ stdev }}</p>
       </div>
+    </Transition>
   </div>
 </template>
 
 <style scoped>
+.v-enter-active,
+.v-leave-active {
+  transition: opacity 0.2s ease;
+}
+
+.v-enter-from,
+.v-leave-to {
+  opacity: 0;
+}
+
 .box {
   cursor: pointer;
 
@@ -137,7 +149,7 @@ const showSources = ref(true);
   backdrop-filter: blur(2px);
 
   color: #333;
-  padding: 10px 20px;
+  padding: 32px;
 }
 
 .average {