body {
  font-family: 'Noto Sans KR', sans-serif;
  background-color: #f9f9f9;
  color: #333;
  margin: 0;
  padding: 0;
}
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<style>
  body {
    font-family: sans-serif;
    margin: 0;
    padding: 20px;
    max-width: 600px;
    margin: auto;
  }
  input, textarea, button {
    width: 100%;
    margin: 5px 0;
    padding: 10px;
    font-size: 1em;
  }
</style>
header, footer {
  background-color: #ffcccb;
  padding: 20px;
  text-align: center;
}
nav a {
  margin: 0 10px;
  text-decoration: none;
  color: #444;
}
main {
  padding: 30px;
}
#chat-box {
  border: 1px solid #ccc;
  padding: 15px;
  height: 300px;
  overflow-y: auto;
  background-color: #fff;
  margin-bottom: 10px;
}
.message {
  margin: 5px 0;
  padding: 8px;
  border-radius: 5px;
}
.message.user {
  background-color: #e0f7fa;
  text-align: right;
}
.message.ruby {
  background-color: #ffe0e0;
  text-align: left;
}
#user-input {
  width: 70%;
  padding: 10px;
}
button {
  padding: 10px 15px;
  background-color: #ff9999;
  border: none;
  color: white;
  cursor: pointer;
}
body {
  font-family: 'Arial', sans-serif;
  background: #f9f9f9;
  margin: 0;
  padding: 0;
}

header, footer {
  background: #333;
  color: white;
  padding: 10px;
  text-align: center;
}

main {
  padding: 20px;
}

a {
  color: #0077cc;
  text-decoration: none;
}
#chatbox {
  background: #fff;
  border: 1px solid #ccc;
  padding: 15px;
  max-width: 600px;
  margin: auto;
}

#messages div {
  margin-bottom: 10px;
}