:root {
  color-scheme: dark;
  --bg: #0d1117;
  --panel: #161b22;
  --panel-strong: #21262d;
  --text: #f0f6fc;
  --muted: #8b949e;
  --accent: #58a6ff;
  --success: #3fb950;
  --warning: #d29922;
  --error: #f85149;
  font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  min-height: 100vh;
  background: radial-gradient(circle at top left, rgba(88, 166, 255, 0.16), transparent 32rem), var(--bg);
  color: var(--text);
}

.login-only {
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
}

a {
  color: inherit;
  text-decoration: none;
}

.site-header {
  display: flex;
  align-items: center;
  gap: 1rem;
  padding: 1rem clamp(1rem, 4vw, 3rem);
  background: rgba(13, 17, 23, 0.86);
  border-bottom: 1px solid var(--panel-strong);
  backdrop-filter: blur(14px);
  position: sticky;
  top: 0;
}

.brand {
  font-weight: 800;
  letter-spacing: 0.04em;
}

.main-nav {
  display: flex;
  flex: 1;
  flex-wrap: wrap;
  gap: 0.75rem;
}

.main-nav a,
button {
  border: 1px solid var(--panel-strong);
  border-radius: 999px;
  padding: 0.55rem 0.9rem;
  background: var(--panel);
  color: var(--text);
}

button {
  cursor: pointer;
  font: inherit;
}

button:hover,
.main-nav a:hover {
  border-color: var(--accent);
}

.logout-form {
  margin: 0;
}

.page {
  width: min(1100px, calc(100% - 2rem));
  margin: 0 auto;
  padding: 3rem 0;
}

.hero,
.card {
  border: 1px solid var(--panel-strong);
  border-radius: 24px;
  background: rgba(22, 27, 34, 0.88);
  box-shadow: 0 24px 80px rgba(0, 0, 0, 0.28);
}

.hero {
  padding: clamp(2rem, 7vw, 5rem);
  margin-bottom: 1.5rem;
  text-align: center;
}

.hero h1,
.card h1 {
  margin: 0 0 1rem;
  font-size: clamp(2rem, 8vw, 4.5rem);
  line-height: 1;
}

.eyebrow {
  margin: 0 0 0.75rem;
  color: var(--accent);
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.12em;
}

.grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 1rem;
}

.dashboard-grid {
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
}

.card {
  display: block;
  padding: 1.5rem;
}

.dashboard-grid .card {
  text-align: center;
}

.card h2 {
  margin-top: 0;
}

.card p,
.hero p {
  color: var(--muted);
  line-height: 1.7;
}

.login-card {
  width: 100%;
  max-width: 460px;
  margin: 0 auto;
  text-align: center;
}

.login-only .page {
  width: min(460px, calc(100% - 2rem));
  margin: 0 auto;
  padding: 0;
}

.login-only .login-card {
  width: 100%;
}

.form-stack {
  display: grid;
  gap: 0.75rem;
}

.login-form {
  justify-items: center;
}

.login-form label {
  width: 100%;
  max-width: 360px;
  text-align: center;
}

input {
  width: 100%;
  border: 1px solid var(--panel-strong);
  border-radius: 14px;
  padding: 0.85rem 1rem;
  background: #0d1117;
  color: var(--text);
  font: inherit;
}

.login-form input,
.login-form button {
  width: 100%;
  max-width: 360px;
  text-align: center;
}

.flash-list {
  display: grid;
  gap: 0.75rem;
  margin-bottom: 1rem;
}

.flash {
  margin: 0;
  border-radius: 14px;
  padding: 0.85rem 1rem;
  background: var(--panel);
  border: 1px solid var(--panel-strong);
}

.flash-success {
  border-color: var(--success);
}

.flash-warning {
  border-color: var(--warning);
}

.flash-error {
  border-color: var(--error);
}

.quiz-card {
  width: min(780px, 100%);
  margin: 0 auto;
}

.quiz-card h1 {
  font-size: clamp(2.25rem, 6vw, 3.8rem);
}

.difficulty-panel {
  display: flex;
  flex-wrap: wrap;
  gap: 0.6rem;
  margin: 0 0 1.5rem;
  padding: 0.45rem;
  border: 1px solid var(--panel-strong);
  border-radius: 18px;
  background: rgba(13, 17, 23, 0.45);
}

.difficulty-pill {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 40px;
  padding: 0.5rem 0.85rem;
  border: 1px solid transparent;
  border-radius: 999px;
  color: var(--muted);
  font-weight: 700;
}

.difficulty-pill:hover {
  border-color: var(--accent);
  color: var(--text);
}

.difficulty-pill.is-active {
  border-color: var(--accent);
  background: rgba(88, 166, 255, 0.14);
  color: var(--text);
}

.quiz-form {
  display: grid;
  gap: 1.25rem;
}

.quiz-form fieldset {
  display: grid;
  gap: 1rem;
  margin: 0;
  padding: 0;
  border: 0;
}

.quiz-form legend {
  margin-bottom: 0.25rem;
  font-size: clamp(1.25rem, 4vw, 1.8rem);
  font-weight: 800;
  line-height: 1.25;
}

.quiz-options {
  display: grid;
  gap: 0.75rem;
}

.quiz-option {
  display: grid;
  grid-template-columns: auto minmax(0, 1fr);
  gap: 0.75rem;
  align-items: center;
  min-height: 54px;
  padding: 0.85rem 1rem;
  border: 1px solid var(--panel-strong);
  border-radius: 14px;
  background: rgba(13, 17, 23, 0.58);
  cursor: pointer;
}

.quiz-option input {
  width: auto;
  margin: 0;
  accent-color: var(--accent);
}

.quiz-option span {
  overflow-wrap: anywhere;
  line-height: 1.4;
}

.quiz-option:hover,
.quiz-option.is-selected {
  border-color: var(--accent);
}

.quiz-option.is-correct-answer {
  border-color: var(--success);
}

.quiz-result,
.quiz-empty {
  display: grid;
  gap: 0.35rem;
  margin: 1.25rem 0;
  padding: 1rem;
  border: 1px solid var(--panel-strong);
  border-radius: 16px;
  background: rgba(13, 17, 23, 0.55);
}

.quiz-result.is-correct {
  border-color: var(--success);
}

.quiz-result.is-wrong {
  border-color: var(--warning);
}

.quiz-result span,
.quiz-empty p {
  color: var(--muted);
  line-height: 1.55;
}

.quiz-actions {
  display: flex;
  justify-content: center;
}

.quiz-actions button,
.button-link {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-width: 180px;
  min-height: 42px;
  border: 1px solid var(--panel-strong);
  border-radius: 999px;
  padding: 0.55rem 1rem;
  background: var(--panel);
  color: var(--text);
  font: inherit;
}

.button-link:hover {
  border-color: var(--accent);
}

.quiz-statistics {
  display: grid;
  gap: 1rem;
  margin-top: 1.75rem;
  padding-top: 1.5rem;
  border-top: 1px solid var(--panel-strong);
}

.quiz-statistics h2,
.participant-stats h3 {
  margin: 0;
}

.stat-summary {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 0.75rem;
}

.stat-summary div {
  display: grid;
  gap: 0.25rem;
  min-width: 0;
  padding: 0.85rem;
  border: 1px solid var(--panel-strong);
  border-radius: 14px;
  background: rgba(13, 17, 23, 0.48);
}

.stat-summary span,
.stat-summary small,
.participant-stats p {
  color: var(--muted);
}

.stat-summary strong {
  overflow-wrap: anywhere;
  font-size: 1.35rem;
}

.participant-stats {
  display: grid;
  gap: 0.75rem;
}

.stats-table-wrap {
  overflow-x: auto;
  border: 1px solid var(--panel-strong);
  border-radius: 14px;
}

.stats-table {
  width: 100%;
  min-width: 620px;
  border-collapse: collapse;
}

.stats-table th,
.stats-table td {
  padding: 0.8rem 0.9rem;
  border-bottom: 1px solid var(--panel-strong);
  text-align: left;
  vertical-align: top;
}

.stats-table th {
  color: var(--muted);
  font-size: 0.9rem;
  font-weight: 700;
}

.stats-table tr:last-child td {
  border-bottom: 0;
}

.stats-table td {
  overflow-wrap: anywhere;
}

code {
  color: var(--text);
}

@media (max-width: 720px) {
  .site-header {
    align-items: flex-start;
    flex-direction: column;
  }

  .main-nav {
    flex-direction: column;
    width: 100%;
  }

  .difficulty-panel,
  .stat-summary {
    display: grid;
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }
}