Create index.css

static/index.css

@@ -0,0 +1,27 @@
+
+.loader {
+    border: 16px solid #f3f3f3;
+    /* Light grey */
+    border-top: 16px solid #3498db;
+    /* Blue */
+    border-radius: 50%;
+    width: 120px;
+    height: 120px;
+    animation: spin 2s linear infinite;
+    display: none;
+    /* Initially hidden */
+    position: absolute;
+    top: 50%;
+    left: 50%;
+    transform: translate(-50%, -50%);
+}
+
+@keyframes spin {
+    0% {
+        transform: rotate(0deg);
+    }
+
+    100% {
+        transform: rotate(360deg);
+    }
+}