body {
  margin: 0;
  display: flex;
  font-family: sans-serif;
  background: #111;
  color: #eee;
}
.sidebar {
  width: 200px;
  background: #1e1e1e;
  padding: 20px;
  height: 100vh;
}
.sidebar h1 {
  font-size: 1.2rem;
  color: #0ff;
}
.sidebar nav a {
  display: block;
  margin: 10px 0;
  color: #ccc;
  text-decoration: none;
}
.sidebar nav a.active {
  font-weight: bold;
  color: #fff;
}
main {
  flex: 1;
  padding: 20px;
}
section {
  margin-bottom: 30px;
}
textarea, input {
  width: 100%;
  padding: 10px;
  background: #222;
  border: 1px solid #444;
  color: #eee;
  margin-top: 10px;
}
button {
  padding: 10px 20px;
  background: #0ff;
  border: none;
  color: #000;
  font-weight: bold;
  margin-top: 10px;
  cursor: pointer;
}
button:hover {
  background: #0cc;
}
.mensaje {
  color: #0f0;
  font-weight: bold;
  text-align: center;
}