* {
  box-sizing: border-box;
}

body {
  font-family: "Segoe UI", Arial, sans-serif;
  background: #f2f5f9;
  margin: 0;
  color: #333;
}

/* Hiệu ứng */
.fade-in {
  animation: fadeIn 0.8s ease-in;
}

@keyframes fadeIn {
  from {
    opacity: 0;
    transform: translateY(10px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

/* Header */
header {
  background: linear-gradient(135deg, #0a4fa3, #0d6efd);
  color: white;
  padding: 24px 16px;
  text-align: center;
}

.header-container {
  max-width: 1000px;
  margin: auto;
}

header h1 {
  margin: 0;
  font-size: 26px;
}

header p {
  margin-top: 8px;
  font-size: 15px;
}

/* Menu */
nav {
  background: #ffffff;
  border-bottom: 1px solid #ddd;
}

nav ul {
  display: flex;
  list-style: none;
  padding: 10px;
  margin: 0;
  justify-content: center;
  gap: 30px;
}

nav li {
  font-weight: 500;
  cursor: pointer;
  color: #0a4fa3;
}

nav li:hover {
  text-decoration: underline;
}

/* Main */
main {
  max-width: 1000px;
  margin: 20px auto;
  padding: 0 16px;
}

.intro {
  background: white;
  padding: 20px;
  border-left: 5px solid #0a4fa3;
  margin-bottom: 20px;
}

/* Chat */
.chat-section {
  background: white;
  padding: 20px;
}

.chat-box {
  border: 1px solid #ccc;
  height: 350px;
  padding: 10px;
  overflow-y: auto;
  background: #fafafa;
  margin-bottom: 10px;
}

.bot-msg {
  background: #e9f2ff;
  padding: 8px;
  border-radius: 4px;
  margin-bottom: 8px;
}

.user-msg {
  background: #e6ffe6;
  padding: 8px;
  border-radius: 4px;
  margin-bottom: 8px;
}

/* Input */
.input-area textarea {
  width: 100%;
  height: 80px;
  padding: 8px;
  font-size: 14px;
}

button {
  margin-top: 10px;
  padding: 10px 24px;
  background: #0a4fa3;
  color: white;
  border: none;
  cursor: pointer;
  font-size: 14px;
  border-radius: 3px;
}

button:hover {
  background: #083d7a;
}

.note {
  margin-top: 15px;
  font-size: 13px;
  color: #555;
}

/* Footer */
footer {
  background: #ffffff;
  border-top: 1px solid #ddd;
  text-align: center;
  padding: 12px;
  font-size: 13px;
  margin-top: 30px;
}