* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

:root {
  --primary-color: #5dade2;
  --secondary-color: #7f8c8d;
  --danger-color: #e74c3c;
  --success-color: #27ae60;
  --warning-color: #f39c12;
  --background-color: #1a1a1a;
  --text-color: #e0e0e0;
  --border-color: #404040;
  --card-bg: #2d2d2d;
  --input-bg: #242424;
  --hover-bg: #353535;
}

html {
  height: 100%;
  width: 100%;
}

body {
  font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
  background: linear-gradient(135deg, #1a1a2e 0%, #16213e 100%);
  min-height: 100vh;
  color: var(--text-color);
  margin: 0;
  padding: 0;
  width: 100%;
}

.container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 20px;
}

/* Auth Section */
.auth-section {
  display: flex;
  justify-content: center;
  align-items: center;
  min-height: 100vh;
  padding: 20px;
  flex-direction: column;
  width: 100%;
}

.auth-box {
  background: var(--card-bg);
  border-radius: 12px;
  box-shadow: 0 10px 40px rgba(0, 0, 0, 0.5);
  padding: 40px;
  width: 100%;
  max-width: 400px;
  animation: slideUp 0.3s ease-out;
}

@keyframes slideUp {
  from {
    opacity: 0;
    transform: translateY(20px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

.auth-header {
  text-align: center;
  margin-bottom: 30px;
  padding-bottom: 20px;
  border-bottom: 1px solid var(--border-color);
}

.auth-header h1 {
  margin: 0;
  margin-bottom: 8px;
  color: var(--primary-color);
  font-size: 32px;
  font-weight: 700;
  letter-spacing: -0.5px;
}

.auth-subtitle {
  margin: 0;
  font-size: 14px;
  color: var(--secondary-color);
  font-weight: 400;
}

.auth-tabs {
  display: flex;
  gap: 10px;
  margin-bottom: 20px;
  border-bottom: 2px solid var(--border-color);
}

.tab-button {
  flex: 1;
  padding: 12px;
  border: none;
  background: none;
  color: var(--secondary-color);
  font-size: 16px;
  font-weight: 500;
  cursor: pointer;
  border-bottom: 3px solid transparent;
  transition: all 0.3s ease;
}

.tab-button.active {
  color: var(--primary-color);
  border-bottom-color: var(--primary-color);
}

.tab-content {
  display: none;
}

.tab-content.active {
  display: block;
  animation: fadeIn 0.3s ease-out;
}

@keyframes fadeIn {
  from {
    opacity: 0;
  }
  to {
    opacity: 1;
  }
}

.auth-box form {
  display: flex;
  flex-direction: column;
  gap: 15px;
}

.auth-box input {
  padding: 12px;
  border: 2px solid var(--border-color);
  border-radius: 6px;
  font-size: 14px;
  transition: border-color 0.3s ease;
  background: var(--input-bg);
  color: var(--text-color);
}

.auth-box input:focus {
  outline: none;
  border-color: var(--primary-color);
  box-shadow: 0 0 0 3px rgba(93, 173, 226, 0.2);
}

.demo-info {
  display: none;
  text-align: center;
  font-size: 12px;
  color: var(--secondary-color);
  margin-top: 15px;
  padding: 10px;
  background: var(--input-bg);
  border-radius: 6px;
}

.hint-text {
  text-align: center;
  font-size: 12px;
  color: var(--secondary-color);
  margin-top: 10px;
  padding: 8px;
  background: var(--input-bg);
  border-radius: 4px;
  border-left: 3px solid var(--primary-color);
}

/* App Section */
.app-section {
  padding-top: 0;
  min-height: calc(100vh - 80px);
}

#todoPage,
#adminPage {
  display: none;
}

#todoPage.active,
#adminPage.active {
  display: block;
}

.navbar {
  background: var(--card-bg);
  padding: 20px;
  border-radius: 12px 12px 0 0;
  display: flex;
  justify-content: space-between;
  align-items: center;
  box-shadow: 0 2px 8px rgba(0, 0, 0, 0.3);
  margin-bottom: 0;
}

.navbar h1 {
  color: var(--primary-color);
  margin: 0;
}

.navbar-right {
  display: flex;
  align-items: center;
  gap: 15px;
}

.navbar-right span {
  font-size: 14px;
  color: var(--secondary-color);
}

/* Sections */
.section {
  background: var(--card-bg);
  padding: 30px;
  margin-bottom: 20px;
  border-radius: 12px;
  box-shadow: 0 2px 8px rgba(0, 0, 0, 0.3);
}

.section h2 {
  color: var(--primary-color);
  margin-bottom: 20px;
  font-size: 24px;
  border-bottom: 2px solid var(--border-color);
  padding-bottom: 10px;
}

.section h3 {
  color: var(--text-color);
  margin: 15px 0 10px 0;
  font-size: 18px;
}

/* Buttons */
.btn {
  padding: 10px 16px;
  border: none;
  border-radius: 6px;
  font-size: 14px;
  font-weight: 500;
  cursor: pointer;
  transition: all 0.3s ease;
  display: inline-block;
}

.btn-primary {
  background: var(--primary-color);
  color: white;
}

.btn-primary:hover {
  background: #2980b9;
  transform: translateY(-2px);
  box-shadow: 0 4px 12px rgba(52, 152, 219, 0.3);
}

.btn-secondary {
  background: var(--secondary-color);
  color: white;
}

.btn-secondary:hover {
  background: #7f8c8d;
}

.btn-danger {
  background: var(--danger-color);
  color: white;
}

.btn-danger:hover {
  background: #c0392b;
}

.btn-success {
  background: var(--success-color);
  color: white;
}

.btn-success:hover {
  background: #229954;
}

.btn-warning {
  background: var(--warning-color);
  color: white;
}

.btn-warning:hover {
  background: #e67e22;
}

.btn-small {
  padding: 6px 12px;
  font-size: 12px;
}

.btn:disabled,
.btn.loading {
  opacity: 0.6;
  cursor: not-allowed;
  transform: none !important;
}

.btn.loading {
  position: relative;
  color: transparent;
}

.btn.loading::after {
  content: '';
  position: absolute;
  width: 16px;
  height: 16px;
  top: 50%;
  left: 50%;
  margin-left: -8px;
  margin-top: -8px;
  border: 2px solid transparent;
  border-radius: 50%;
  border-top-color: white;
  animation: spin 0.6s linear infinite;
}

@keyframes spin {
  0% { transform: rotate(0deg); }
  100% { transform: rotate(360deg); }
}

/* Todo Input Group */
.todo-input-group {
  display: flex;
  gap: 10px;
  margin-bottom: 20px;
  flex-wrap: wrap;
}

.todo-input-group input {
  flex: 1;
  min-width: 150px;
  padding: 12px;
  border: 2px solid var(--border-color);
  border-radius: 6px;
  font-size: 14px;
  background: var(--input-bg);
  color: var(--text-color);
}

.todo-input-group input:focus {
  outline: none;
  border-color: var(--primary-color);
  box-shadow: 0 0 0 3px rgba(93, 173, 226, 0.2);
}

.todo-input-group button {
  padding: 12px 24px;
}

/* Todo List */
.todo-list {
  list-style: none;
}

.todo-item {
  background: var(--input-bg);
  padding: 16px;
  border-radius: 8px;
  margin-bottom: 10px;
  display: flex;
  justify-content: space-between;
  align-items: center;
  border-left: 4px solid var(--primary-color);
  transition: all 0.3s ease;
}

.todo-item:hover {
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.3);
  transform: translateY(-2px);
  background: var(--hover-bg);
}

.todo-item.completed {
  opacity: 0.6;
  border-left-color: var(--success-color);
}

.todo-item.completed .todo-title {
  text-decoration: line-through;
  color: var(--secondary-color);
}

.todo-content {
  flex: 1;
}

.todo-title {
  font-weight: 600;
  color: var(--text-color);
  margin-bottom: 4px;
  font-size: 16px;
}

.todo-description {
  color: var(--secondary-color);
  font-size: 14px;
}

.todo-actions {
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
  justify-content: flex-end;
}

.todo-checkbox {
  width: 24px;
  height: 24px;
  cursor: pointer;
  margin-right: 12px;
  accent-color: var(--primary-color);
}

/* Admin Controls */
.admin-controls {
  margin-bottom: 20px;
}

.form-group {
  background: var(--input-bg);
  padding: 20px;
  border-radius: 8px;
  margin-bottom: 20px;
  border: 2px solid var(--border-color);
}

.form-group input,
.form-group label {
  display: block;
  width: 100%;
  margin-bottom: 12px;
  padding: 10px;
  border: 2px solid var(--border-color);
  border-radius: 6px;
  font-size: 14px;
  background: var(--card-bg);
  color: var(--text-color);
}

.form-group input[type="checkbox"] {
  width: auto;
  margin-right: 8px;
  display: inline-block;
}

.form-group label {
  border: none;
  padding: 0;
  display: flex;
  align-items: center;
  margin-bottom: 12px;
}

.form-group input:focus {
  outline: none;
  border-color: var(--primary-color);
}

/* Users Table */
.users-table {
  width: 100%;
  border-collapse: collapse;
  margin-top: 20px;
}

.users-table thead {
  background: var(--background-color);
}

.users-table th {
  padding: 12px;
  text-align: left;
  font-weight: 600;
  border-bottom: 2px solid var(--border-color);
  color: var(--text-color);
}

.users-table td {
  padding: 12px;
  border-bottom: 1px solid var(--border-color);
}

.users-table tr:hover {
  background: var(--hover-bg);
}

.user-actions {
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
}

/* Error Messages */
.error-message {
  color: #ff6b6b;
  font-size: 14px;
  margin-top: 10px;
  padding: 10px;
  background: rgba(231, 76, 60, 0.15);
  border-left: 4px solid var(--danger-color);
  border-radius: 4px;
  display: none;
}

.error-message.show {
  display: block;
  animation: slideDown 0.3s ease-out;
}

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

.success-message {
  color: #51cf66;
  font-size: 14px;
  margin-top: 10px;
  padding: 10px;
  background: rgba(39, 174, 96, 0.15);
  border-left: 4px solid var(--success-color);
  border-radius: 4px;
  display: none;
}

.success-message.show {
  display: block;
  animation: slideDown 0.3s ease-out;
}

/* Modal */
.modal {
  position: fixed;
  z-index: 1000;
  left: 0;
  top: 0;
  width: 100%;
  height: 100%;
  background: rgba(0, 0, 0, 0.7);
  animation: fadeIn 0.3s ease-out;
}

.modal-content {
  background: var(--card-bg);
  margin: 5% auto;
  padding: 30px;
  border-radius: 12px;
  width: 90%;
  max-width: 400px;
  box-shadow: 0 10px 40px rgba(0, 0, 0, 0.5);
}

.close {
  color: var(--secondary-color);
  float: right;
  font-size: 28px;
  font-weight: bold;
  cursor: pointer;
  transition: color 0.3s ease;
}

.close:hover {
  color: var(--danger-color);
}

.modal-content form {
  display: flex;
  flex-direction: column;
  gap: 15px;
  margin-top: 20px;
}

.modal-content input,
.modal-content label {
  padding: 10px;
  border: 2px solid var(--border-color);
  border-radius: 6px;
  font-size: 14px;
  background: var(--input-bg);
  color: var(--text-color);
}

.modal-content input:focus {
  outline: none;
  border-color: var(--primary-color);
  box-shadow: 0 0 0 3px rgba(93, 173, 226, 0.2);
}

.modal-content label {
  border: none;
  padding: 0;
  display: flex;
  align-items: center;
}

.modal-content input[type="checkbox"] {
  width: auto;
  margin-right: 8px;
  border: none;
}

/* Footer */
.app-footer {
  background: var(--card-bg);
  border-top: 1px solid var(--border-color);
  padding: 20px;
  margin-top: 40px;
  text-align: center;
}

.footer-content {
  max-width: 1200px;
  margin: 0 auto;
}

.footer-content p {
  margin: 5px 0;
  color: var(--secondary-color);
  font-size: 14px;
}

.footer-version {
  font-size: 12px;
  opacity: 0.8;
}

.footer-version span {
  font-weight: 600;
  color: var(--primary-color);
}

/* Responsive Design */
@media (max-width: 768px) {
  .container {
    padding: 10px;
  }

  .auth-box {
    padding: 25px;
  }

  .navbar {
    flex-direction: column;
    gap: 15px;
    text-align: center;
  }

  .navbar-right {
    flex-direction: column;
    width: 100%;
  }

  .navbar-right button {
    width: 100%;
  }

  .todo-input-group {
    flex-direction: column;
  }

  .todo-input-group input,
  .todo-input-group button {
    width: 100%;
  }

  .todo-item {
    flex-direction: column;
    align-items: flex-start;
  }

  .todo-actions {
    width: 100%;
    margin-top: 10px;
  }

  .users-table {
    font-size: 12px;
  }

  .users-table th,
  .users-table td {
    padding: 8px;
  }

  .user-actions {
    flex-direction: column;
  }

  .user-actions button {
    width: 100%;
  }
}