/* Thiết lập kiểu cơ bản */
body {
  font-family: Arial, Helvetica, sans-serif;
  background-color: #f8f9fa; /* Màu nền trang */
  height: 100vh;
  margin: 0;
  display: flex;
  flex-direction: column;
  justify-content: space-between;
}

h1 {
  text-align: center;
  color:rgb(42, 132, 235);
  margin-top: 20px;
}
h2 {
  text-align: center;
  color: black;
}

button {
  cursor: pointer;
  border: none;
  outline: none;
}

a {
  text-decoration: none;
}

/* Kiểu cho trang danh sách môn học */
.materials-container {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 20px;
  padding: 20px;
}

.material-card {
  width: 250px;
  padding: 30px;
  background-color: #fff;
  box-shadow: 0 4px 10px rgba(0, 0, 0, 0.1);
  border-radius: 8px;
  text-align: center;
  transition: transform 0.3s ease;
}

.material-card:hover {
  transform: scale(1.05);
}

.material-card h3 {
  font-size: 18px;
  color: #333;
  margin-bottom: 15px;
}

.material-card button {
  font-size: 14px;
  padding: 10px 20px;
  color: #0056b3;
  background-color: #fff;
  border: 1px solid #0056b3;
  border-radius: 5px;
  transition: background-color 0.3s ease, color 0.3s ease;
}

.material-card button:hover {
  background-color: #0056b3;
  color: #fff;
}

/* Kiểu cho trang chi tiết bài học */
.lessons-container {
  display: flex;
  justify-content: space-between; /* Giãn đều nội dung sang 2 bên */

  height: 520px;
  width: 80%;
  max-width: 1000px;
  margin: 20px auto;
  border-radius: 8px;
  overflow: hidden;
  box-shadow: 0 4px 10px rgba(0, 0, 0, 0.1);
  padding: 20px; /* Thêm khoảng cách bên trong */
  background-color: #fff; /* Nền trắng (tuỳ chỉnh) */
}

.sidebar {
  width: 200px;
  background-color: #f5f5f5;
  padding: 0px;
  border-right: 1px solid #ddd;
}

.sidebar h2 {
  font-size: 18px;
  color: #333;
}

.sidebar ul {
  list-style: none;
  padding: 0;
  margin-top: 20px;
}

.sidebar li {
  font-size: 16px;
  color: #333;
  margin-bottom: 10px;
  padding: 12px 16px;
  border-radius: 5px;
  cursor: pointer;
  transition: background-color 0.3s ease;
}

.sidebar li:hover {
  background-color: #e0e0e0;
}

.sidebar li.active {
  background-color: #d0e2ff;
  color: #0056b3;
  font-weight: bold;
}

.content-area3 {
  flex-grow: 1;
  background-color: #ffffff;
}

.content-area3 h2 {
  font-size: 24px;
  color: #333;
  margin-bottom: 20px;
}

#content-display {
  color: #666;
}

#content-display p {
  font-size: 16px;
  line-height: 1.6;
}

/* Nút quay lại */
.back-button {
  display: inline-block;

  padding: 10px 20px;
  font-size: 14px;
  color: #0056b3;
  background-color: #fff;
  border: 1px solid #0056b3;
  border-radius: 5px;
  transition: background-color 0.3s ease, color 0.3s ease;
}

.back-button:hover {
  background-color: #0056b3;
  color: #fff;
}
/* Container cho nút Back to list */
.back-button-container {
display: flex;
justify-content: center;
margin-top: auto;
padding: 20px;
}

/* Kiểu dáng cho nút Back to list */
.back-button {
font-size: 14px;
color: #0056b3;
background-color: #ffffff;
border: 1px solid #0056b3;
padding: 10px 20px;
border-radius: 5px;
text-decoration: none;
transition: background-color 0.3s ease, color 0.3s ease;
}

.back-button:hover {
background-color: #0056b3;
color: #ffffff;
}