/* Reset CSS */
* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
  font-family: Arial, sans-serif;
}

body {
  background: linear-gradient(135deg, #4facfe, #00f2fe);
  height: 100vh;
  display: flex;
  justify-content: center;
  align-items: center;
}

.login-container {
  display: flex;
  justify-content: center;
  align-items: center;
  width: 100%;
}

.login-box {
  background: #fff;
  padding: 40px 30px;
  border-radius: 12px;
  box-shadow: 0 8px 25px rgba(0,0,0,0.2);
  width: 350px;
  text-align: center;
}

.login-box h2 {
  margin-bottom: 25px;
  color: #333;
}

.login-box input {
  width: 100%;
  padding: 12px 15px;
  margin: 10px 0;
  border: 1px solid #ccc;
  border-radius: 8px;
  outline: none;
  font-size: 14px;
  transition: 0.3s;
}

.login-box input:focus {
  border-color: #4facfe;
  box-shadow: 0 0 6px rgba(79, 172, 254, 0.5);
}

.login-box button {
  width: 100%;
  padding: 12px 15px;
  background: linear-gradient(135deg, #4facfe, #00f2fe);
  border: none;
  border-radius: 8px;
  color: #fff;
  font-size: 16px;
  cursor: pointer;
  transition: 0.3s;
}

.login-box button:hover {
  opacity: 0.9;
}

.error {
  margin-top: 10px;
  color: red;
  font-size: 14px;
}
/* Responsive cho màn hình nhỏ hơn 768px (tablet, mobile) */
@media (max-width: 768px) {
  .sidebar {
    width: 100%;
    height: auto;
    position: relative;
  }

  .sidebar ul {
    display: flex;
    overflow-x: auto;
  }

  .content {
    margin-left: 0;
    padding: 10px;
  }

  .card {
    width: 100%;
    margin-bottom: 15px;
  }

  table {
    font-size: 14px;
    display: block;
    overflow-x: auto;
    white-space: nowrap;
  }
}

/* Responsive cho màn hình rất nhỏ (dưới 480px) */
@media (max-width: 480px) {
  .card h2 {
    font-size: 18px;
  }

  table th, table td {
    font-size: 12px;
    padding: 6px;
  }

  .btn {
    padding: 8px 12px;
    font-size: 14px;
  }
}