body {
  background:#0d1117;
  color:#fff;
  font-family:Arial;
}
.container {
  max-width:900px;
  margin:auto;
}
.topbar {
  background:#161b22;
  padding:15px;
  position:sticky;
  top:0;
}
input, textarea, select {
  width:100%;
  margin:10px 0;
  padding:12px;
}
.tab { display:none; }
.btn {
  background:#238636;
  padding:12px;
  border:none;
  color:#fff;
}
.danger {
  background:#da3633;
}