body {
  font-family: Arial, sans-serif;
  padding: 20px;
  background: #f7f7f7;
  color: #222;
}

body.dark {
  background: #111;
  color: #eee;
}

input, button {
  padding: 8px;
  margin: 5px 0;
  width: 100%;
  max-width: 400px;
}

#calendar {
  max-width: 800px;
  margin: 40px auto;
}

.container {
  max-width: 800px;
  margin: auto;
  padding: 20px;
  border-radius: 10px;
  background: #fff;
}

body.dark .container {
  background: #222;
}