body {
  background: #111;
  color: #fff;
  font-family: Arial, sans-serif;
}

.chat {
  width: 320px;
  margin: 40px auto;
  background: #000;
  padding: 15px;
  border-radius: 8px;
}

#messages {
  height: 200px;
  border: 1px solid #333;
  padding: 5px;
  margin-bottom: 10px;
  overflow-y: auto;
}

input, button {
  width: 100%;
  margin-bottom: 6px;
  padding: 6px;
  box-sizing: border-box;
}