body {
  margin: 0;
  font-family: "Segoe UI", sans-serif;
  background-color: #f4f6fa;
  color: #222;
}

header {
  background-color: #ffffff;
  color: #1e3a8a;
  box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
  padding: 15px 40px;
}

.container.header-container {
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.logo img {
  height: 50px;
}

.nav-links {
  display: flex;
  list-style: none;
  gap: 20px;
  margin: 0;
  padding: 0;
}

.nav-links li a {
  text-decoration: none;
  color: #1e3a8a;
  font-weight: 500;
  transition: 0.3s;
}

.nav-links li a:hover,
.nav-links li a.active {
  color: #1e88e5;
}

/* Nội dung chính */
.discussion-container {
  display: flex;
  gap: 30px;
  margin-top: 40px;
  margin-bottom: 60px;
}

.user-list {
  width: 250px;
  background: #1e3a8a;
  color: white;
  padding: 20px;
  border-radius: 8px;
}

.user-list ul {
  list-style: none;
  padding: 0;
  margin: 0;
}

.user-list li {
  padding: 8px 0;
}

.chat-section {
  flex: 1;
  background: #ffffff;
  padding: 20px;
  border-radius: 8px;
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.05);
}

.chat-box {
  height: 400px;
  overflow-y: auto;
  border: 1px solid #ccc;
  border-radius: 6px;
  padding: 15px;
  background-color: #f9fafc;
}

.username {
  color: #1e88e5;
  margin-bottom: 0;
}

.chat-input {
  margin-top: 20px;
}

.chat-input textarea {
  width: 100%;
  height: 80px;
  padding: 10px;
  border: 1px solid #ccc;
  border-radius: 6px;
  resize: none;
}

.chat-input button {
  margin-top: 10px;
  background-color: #1e88e5;
  color: white;
  border: none;
  padding: 10px 20px;
  border-radius: 6px;
  font-weight: bold;
  cursor: pointer;
  transition: background 0.3s ease;
}

.chat-input button:hover {
  background-color: #1669c1;
}

footer {
  text-align: center;
  padding: 20px;
  background-color: #1e3a8a;
  color: white;
}