add css

apps/core/static/css/accordion.css

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+/* see https://supfort.com/pure-css-accordion-without-javascript */
+
+label {
+    display: block;
+    padding: 8px 22px;
+    margin: 0 0 1px 0;
+    cursor: pointer;
+    background: #6AAB95;
+    border-radius: 3px;
+    color: #FFF;
+    transition: ease .5s;
+}
+
+label:hover {
+    background: #4E8774;
+}
+
+.content {
+    background: #E2E5F6;
+    padding: 10px 25px;
+    border: 1px solid #A7A7A7;
+    margin: 0 0 1px 0;
+    border-radius: 3px;
+}
+
+input + label + .content {
+    display: none;
+}
+
+input:checked + label + .content {
+    display: block;
+}
+
+input[type="checkbox"] {
+    display: none;
+}

apps/core/static/css/style.css

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+.form-box {
+  max-width: 500px;
+  margin: auto;
+  padding: 50px;
+  background: #ffffff;
+  border: 10px solid #f2f2f2;
+}
+input, textarea {
+  width: 100%;
+}
+h3 {
+  padding-top: 30px;
+}

apps/core/static/css/topnav.css

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+/* see https://www.w3schools.com/howto/howto_js_topnav_responsive.asp */
+
+.topnav {
+  overflow: hidden;
+  background-color: #333;
+}
+
+.topnav a {
+  float: left;
+  color: #f2f2f2;
+  text-align: center;
+  padding: 14px 16px;
+  text-decoration: none;
+  font-size: 17px;
+}
+
+.topnav a:hover {
+  background-color: #ddd;
+  color: black;
+}
+
+.topnav a.active {
+  background-color: #4CAF50;
+  color: white;
+}
+
+.topnav .right {
+  float: right !important;
+}