:root {
  --bg: #0f172a;
  --bg-elevated: #020617;
  --accent: #38bdf8;
  --accent-soft: rgba(56, 189, 248, 0.12);
  --accent-strong: rgba(56, 189, 248, 0.3);
  --text-main: #e5e7eb;
  --text-muted: #9ca3af;
  --error: #f97373;
  --border-subtle: rgba(148, 163, 184, 0.35);
  --radius-lg: 18px;
  --radius-sm: 10px;
  --shadow-soft: 0 18px 45px rgba(15, 23, 42, 0.75);
  --transition-fast: 0.18s ease-out;
  --font-main: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI",
    sans-serif;
}

*,
*::before,
*::after {
  box-sizing: border-box;
}

body {
  margin: 0;
  min-height: 100vh;
  font-family: var(--font-main);
  background: radial-gradient(circle at top, #1f2937 0, var(--bg) 55%, #020617 100%);
  color: var(--text-main);
  display: flex;
  justify-content: center;
  align-items: stretch;
}

.app {
  width: 100%;
  max-width: 720px;
  padding: 32px 16px;
  display: flex;
  flex-direction: column;
  gap: 20px;
}

.app__header {
  text-align: center;
}

.app__header h1 {
  margin: 0;
  font-size: 1.8rem;
  letter-spacing: 0.03em;
  background: linear-gradient(120deg, #f9fafb, #bae6fd);
  -webkit-background-clip: text;
  color: transparent;
}

.app__main {
  flex: 1;
  display: flex;
  flex-direction: column;
  gap: 16px;
}

.card {
  background: linear-gradient(145deg, rgba(15, 23, 42, 0.96), #020617);
  border-radius: var(--radius-lg);
  padding: 24px 22px 22px;
  box-shadow: var(--shadow-soft);
  border: 1px solid var(--border-subtle);
  backdrop-filter: blur(18px);
}

.card--hidden {
  display: none;
}

.field-label {
  display: block;
  margin-bottom: 6px;
  font-size: 0.9rem;
  color: var(--text-muted);
}

.text-input {
  width: 100%;
  padding: 10px 12px;
  border-radius: var(--radius-sm);
  border: 1px solid rgba(148, 163, 184, 0.5);
  background-color: rgba(15, 23, 42, 0.85);
  color: var(--text-main);
  font-size: 1rem;
  outline: none;
  transition: border-color var(--transition-fast), box-shadow var(--transition-fast),
    background-color var(--transition-fast), transform var(--transition-fast);
}

.text-input::placeholder {
  color: var(--text-muted);
}

.text-input:focus {
  border-color: var(--accent);
  box-shadow: 0 0 0 1px rgba(56, 189, 248, 0.4);
  background-color: rgba(15, 23, 42, 0.98);
  transform: translateY(-1px);
}

.primary-button,
.secondary-button {
  margin-top: 14px;
  padding: 10px 16px;
  border-radius: 999px;
  border: none;
  cursor: pointer;
  font-size: 0.95rem;
  font-weight: 600;
  letter-spacing: 0.02em;
  transition: background-color var(--transition-fast), transform var(--transition-fast),
    box-shadow var(--transition-fast), color var(--transition-fast),
    border-color var(--transition-fast), opacity var(--transition-fast);
}

.primary-button {
  background: radial-gradient(circle at top left, #38bdf8, #0ea5e9);
  color: #0b1120;
  box-shadow: 0 10px 30px rgba(56, 189, 248, 0.4);
}

.primary-button:hover:not(:disabled) {
  transform: translateY(-1px);
  box-shadow: 0 16px 40px rgba(56, 189, 248, 0.55);
}

.primary-button:disabled {
  opacity: 0.5;
  cursor: default;
  box-shadow: none;
}

.secondary-button {
  background-color: transparent;
  color: var(--accent);
  border: 1px solid rgba(56, 189, 248, 0.6);
}

.secondary-button:hover {
  background-color: var(--accent-soft);
  transform: translateY(-1px);
}

.secondary-button--small {
  margin-top: 0;
  padding: 6px 12px;
  font-size: 0.8rem;
}

.error-message {
  min-height: 1.2em;
  margin-top: 8px;
  font-size: 0.85rem;
  color: var(--error);
}

.auth-buttons {
  display: flex;
  gap: 8px;
  margin-top: 14px;
}

.auth-hint {
  margin-top: 10px;
  font-size: 0.85rem;
  color: var(--text-muted);
}

.quiz-header {
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
  align-items: center;
  gap: 8px;
  margin-bottom: 18px;
  font-size: 0.9rem;
  color: var(--text-muted);
}

.quiz-header-actions {
  display: flex;
  align-items: center;
  gap: 8px;
}

.quiz-progress {
  display: flex;
  flex-direction: column;
  gap: 4px;
  min-width: 0;
}

.quiz-progress-text {
  font-size: 0.9rem;
}

.quiz-progress-bar {
  width: 120px;
  height: 6px;
  background: rgba(148, 163, 184, 0.25);
  border-radius: 3px;
  overflow: hidden;
}

.quiz-progress-fill {
  height: 100%;
  background: var(--accent);
  border-radius: 3px;
  transition: width var(--transition-fast);
}

.session-mode-options {
  margin: 10px 0 16px;
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.session-mode-options .radio-label {
  display: flex;
  align-items: center;
  gap: 10px;
  cursor: pointer;
  font-size: 1rem;
  color: var(--text-main);
}

.session-mode-options input[type="radio"] {
  accent-color: var(--accent);
}

.session-tag-block {
  margin-bottom: 16px;
}

.session-tag-block .text-input {
  max-width: 320px;
}

.quiz-question h2 {
  margin: 0 0 16px;
  font-size: 1.2rem;
}

.quiz-options {
  display: grid;
  grid-template-columns: 1fr;
  gap: 10px;
  margin-bottom: 16px;
}

.fill-answer-block {
  margin-bottom: 16px;
}

.fill-answer-block.card--hidden {
  display: none;
}

.fill-answer-input {
  max-width: 12rem;
  font-size: 1.25rem;
  text-align: center;
  letter-spacing: 0.1em;
}

.option-button {
  width: 100%;
  text-align: left;
  padding: 10px 12px;
  border-radius: 12px;
  border: 1px solid rgba(148, 163, 184, 0.6);
  background-color: rgba(15, 23, 42, 0.85);
  color: var(--text-main);
  cursor: pointer;
  font-size: 0.98rem;
  transition: background-color var(--transition-fast), border-color var(--transition-fast),
    transform var(--transition-fast), box-shadow var(--transition-fast),
    color var(--transition-fast), opacity var(--transition-fast);
}

.option-button:hover {
  background-color: rgba(15, 23, 42, 0.98);
  border-color: rgba(56, 189, 248, 0.7);
  box-shadow: 0 10px 25px rgba(15, 23, 42, 0.8);
  transform: translateY(-1px);
}

.option-button--selected {
  border-color: rgba(56, 189, 248, 0.95);
  background: linear-gradient(135deg, rgba(56, 189, 248, 0.2), rgba(30, 64, 175, 0.2));
  box-shadow: 0 12px 30px rgba(56, 189, 248, 0.35);
}

.option-button--correct {
  border-color: #4ade80;
  background: linear-gradient(135deg, rgba(34, 197, 94, 0.16), rgba(22, 163, 74, 0.22));
}

.option-button--wrong {
  border-color: #f97373;
  background: linear-gradient(135deg, rgba(248, 113, 113, 0.18), rgba(220, 38, 38, 0.24));
}

.option-button:disabled {
  cursor: default;
  opacity: 0.9;
}

.quiz-controls {
  display: flex;
  justify-content: flex-end;
}

.feedback {
  min-height: 1.2em;
  margin-top: 8px;
  font-size: 0.9rem;
}

.text-input--multiline {
  resize: vertical;
}

.admin-section {
  margin-top: 18px;
}

.admin-section h3 {
  margin: 0 0 10px;
  font-size: 1rem;
}

.admin-question-type-options {
  display: flex;
  gap: 12px;
  margin-bottom: 10px;
}

.admin-question-type-options .radio-label {
  display: flex;
  align-items: center;
  gap: 6px;
  cursor: pointer;
  font-size: 0.95rem;
}

.admin-fill-answer-block.card--hidden,
.admin-options-block.card--hidden,
.edit-fill-answer-block.card--hidden,
.edit-options-block.card--hidden {
  display: none;
}

.admin-correct-answer-input {
  max-width: 8rem;
  font-size: 1.1rem;
}

.admin-create-student {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 10px;
  margin-bottom: 8px;
}

.admin-create-student .text-input {
  max-width: 200px;
}

.admin-options {
  display: grid;
  gap: 8px;
  margin-bottom: 8px;
}

.admin-option-row {
  display: flex;
  flex-direction: column;
}

.admin-stats-wrapper {
  margin-top: 8px;
  max-height: 260px;
  overflow: auto;
  border-radius: var(--radius-sm);
  border: 1px solid rgba(148, 163, 184, 0.4);
}

.admin-stats-table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.9rem;
}

.admin-stats-table th,
.admin-stats-table td {
  padding: 8px 10px;
  border-bottom: 1px solid rgba(148, 163, 184, 0.3);
}

.admin-stats-table thead {
  background-color: rgba(15, 23, 42, 0.9);
}

.admin-stats-table tbody tr:nth-child(even) {
  background-color: rgba(15, 23, 42, 0.8);
}

.admin-student-details {
  margin-top: 14px;
  padding-top: 10px;
  border-top: 1px dashed rgba(148, 163, 184, 0.6);
  font-size: 0.9rem;
  color: var(--text-muted);
}

.admin-student-details h4 {
  margin: 0 0 8px;
  font-size: 0.95rem;
  color: var(--text-main);
}

.admin-student-question-list {
  list-style: none;
  padding-left: 0;
  margin: 0;
  max-height: 220px;
  overflow-y: auto;
}

.admin-student-question-item {
  padding: 6px 0;
  border-bottom: 1px solid rgba(148, 163, 184, 0.25);
}

.admin-student-question-item span {
  display: inline-block;
}

.badge {
  display: inline-block;
  padding: 2px 8px;
  border-radius: 999px;
  font-size: 0.78rem;
  margin-left: 6px;
}

.badge--correct {
  background-color: rgba(34, 197, 94, 0.16);
  color: #bbf7d0;
}

.badge--wrong {
  background-color: rgba(248, 113, 113, 0.18);
  color: #fecaca;
}

/* Modal */
.modal {
  position: fixed;
  inset: 0;
  z-index: 100;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 16px;
}

.modal.card--hidden {
  display: none;
}

.modal-backdrop {
  position: absolute;
  inset: 0;
  background: rgba(2, 6, 23, 0.85);
  cursor: pointer;
}

.modal-content {
  position: relative;
  width: 100%;
  max-width: 560px;
  max-height: 90vh;
  overflow-y: auto;
  background: linear-gradient(145deg, rgba(15, 23, 42, 0.98), #020617);
  border-radius: var(--radius-lg);
  padding: 24px;
  box-shadow: var(--shadow-soft);
  border: 1px solid var(--border-subtle);
}

.modal-content h2 {
  margin: 0 0 16px;
  font-size: 1.2rem;
}

.modal-actions {
  display: flex;
  gap: 10px;
  margin-top: 16px;
}

/* Admin: all questions */
.admin-questions-toolbar {
  display: flex;
  align-items: center;
  gap: 12px;
  margin-bottom: 10px;
  flex-wrap: wrap;
}

.admin-questions-toolbar .radio-label {
  display: flex;
  align-items: center;
  gap: 6px;
  cursor: pointer;
  font-size: 0.9rem;
  color: var(--text-muted);
}

.admin-questions-table-wrapper {
  max-height: 320px;
  overflow: auto;
  border-radius: var(--radius-sm);
  border: 1px solid rgba(148, 163, 184, 0.4);
}

.admin-questions-table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.88rem;
}

.admin-questions-table th,
.admin-questions-table td {
  padding: 8px 10px;
  border-bottom: 1px solid rgba(148, 163, 184, 0.3);
}

.admin-questions-table thead {
  background-color: rgba(15, 23, 42, 0.9);
}

.admin-questions-table tbody tr:hover {
  background-color: rgba(56, 189, 248, 0.08);
}

.admin-questions-table .question-prompt-cell {
  max-width: 280px;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.admin-questions-table .question-tags-cell {
  max-width: 160px;
  font-size: 0.82rem;
  color: var(--text-muted);
}

/* Global loading indicator */
.global-loading {
  position: fixed;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  z-index: 9999;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 12px;
  padding: 20px 28px;
  background: rgba(15, 23, 42, 0.95);
  border-radius: var(--radius-lg);
  border: 1px solid var(--border-subtle);
  box-shadow: var(--shadow-soft);
}

.global-loading.card--hidden {
  display: none;
}

.global-loading-spinner {
  width: 32px;
  height: 32px;
  border: 3px solid rgba(148, 163, 184, 0.3);
  border-top-color: var(--accent);
  border-radius: 50%;
  animation: spin 0.8s linear infinite;
}

.global-loading-text {
  font-size: 0.9rem;
  color: var(--text-muted);
}

@keyframes spin {
  to {
    transform: rotate(360deg);
  }
}

@media (min-width: 640px) {
  .card {
    padding: 26px 26px 24px;
  }
}

/* Responsive: narrow screens */
@media (max-width: 640px) {
  .app {
    padding: 16px 12px;
  }

  .card {
    padding: 18px 14px;
  }

  .app__header h1 {
    font-size: 1.4rem;
  }

  .quiz-header {
    flex-direction: column;
    align-items: flex-start;
    gap: 10px;
  }

  .quiz-header-actions {
    width: 100%;
    flex-wrap: wrap;
  }

  .quiz-header-actions .secondary-button {
    flex: 1;
    min-width: 120px;
  }

  .quiz-progress-bar {
    width: 100%;
    max-width: 200px;
  }

  .primary-button,
  .secondary-button {
    width: 100%;
  }

  .auth-buttons .primary-button {
    width: 100%;
  }

  .admin-create-student {
    flex-direction: column;
  }

  .admin-create-student .text-input,
  .admin-create-student .primary-button {
    width: 100%;
  }

  .session-mode-options {
    gap: 6px;
  }

  .quiz-controls .primary-button {
    width: 100%;
  }

  .option-button {
    width: 100%;
    text-align: left;
  }

  .admin-questions-table .question-prompt-cell {
    max-width: 140px;
  }
}