:root {
  --bg: #0f172a;
  --bg-gradient: linear-gradient(180deg, #0f172a 0%, #111827 35%, #111f2f 100%);
  --surface: rgba(15, 23, 42, 0.75);
  --surface-light: rgba(30, 41, 59, 0.85);
  --surface-strong: rgba(30, 41, 59, 0.95);
  --border: rgba(148, 163, 184, 0.25);
  --shadow: 0 24px 60px rgba(15, 23, 42, 0.5);
  --accent: #ef7e3b;
  --accent-strong: #ea580c;
  --accent-soft: rgba(239, 126, 59, 0.16);
  --text: #e2e8f0;
  --text-invert: #f8fafc;
  --text-muted: #94a3b8;
  --radius: 24px;
  --radius-small: 16px;
  --radius-tiny: 12px;
  --space-xs: clamp(0.4rem, 0.3rem + 0.2vw, 0.6rem);
  --space-sm: clamp(0.75rem, 0.6rem + 0.3vw, 1rem);
  --space-md: clamp(1rem, 0.9rem + 0.4vw, 1.5rem);
  --space-lg: clamp(1.5rem, 1.3rem + 0.6vw, 2.2rem);
  --space-xl: clamp(2.5rem, 2.1rem + 1vw, 3.4rem);
  --font-base: "Outfit", system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
}

* {
  box-sizing: border-box;
}

html,
body {
  height: 100%;
}

body {
  margin: 0;
  font-family: var(--font-base);
  color: var(--text);
  background: var(--bg);
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

body::before {
  content: "";
  position: fixed;
  inset: 0;
  background: var(--bg-gradient);
  z-index: -2;
}

body::after {
  content: "";
  position: fixed;
  inset: 0;
  background: radial-gradient(circle at 20% 20%, rgba(14, 165, 233, 0.12), transparent 45%),
    radial-gradient(circle at 80% 10%, rgba(239, 126, 59, 0.18), transparent 40%),
    radial-gradient(circle at 40% 80%, rgba(45, 212, 191, 0.12), transparent 35%);
  z-index: -1;
  pointer-events: none;
}

img,
svg {
  max-width: 100%;
  display: block;
}

a {
  color: inherit;
}

.hero {
  padding: var(--space-xl) var(--space-lg) var(--space-lg);
}

.hero__content {
  max-width: 960px;
  margin: 0 auto;
  text-align: center;
}

.hero__title {
  margin: 0;
  font-size: clamp(2.5rem, 2.1rem + 1vw, 3.2rem);
  letter-spacing: 0.02em;
  color: var(--text-invert);
}

.hero__subtitle {
  margin: var(--space-sm) auto var(--space-md);
  max-width: 700px;
  color: var(--text-muted);
  font-size: clamp(1rem, 0.9rem + 0.4vw, 1.3rem);
}

.hero__cta {
  display: inline-flex;
  gap: var(--space-sm);
}

.button {
  border: 1px solid transparent;
  border-radius: 999px;
  padding: 0.65rem 1.5rem;
  font-weight: 600;
  background: rgba(148, 163, 184, 0.14);
  color: var(--text-invert);
  cursor: pointer;
  transition: transform 0.15s ease, box-shadow 0.3s ease, background 0.2s ease, border-color 0.2s ease;
}

.button:hover,
.button:focus-visible {
  transform: translateY(-1px);
  box-shadow: 0 14px 36px rgba(15, 23, 42, 0.45);
}

.button--accent {
  background: linear-gradient(135deg, var(--accent-strong), var(--accent));
  border-color: rgba(234, 88, 12, 0.4);
  color: var(--text-invert);
}

.button--accent:hover,
.button--accent:focus-visible {
  background: linear-gradient(135deg, var(--accent), var(--accent-strong));
}

.button--ghost {
  background: rgba(148, 163, 184, 0.1);
  border-color: rgba(148, 163, 184, 0.3);
}

.layout {
  width: min(1320px, calc(100% - 2 * var(--space-lg)));
  margin: 0 auto var(--space-xl);
  display: grid;
  grid-template-columns: minmax(280px, 1fr) minmax(420px, 1.3fr);
  gap: var(--space-lg);
  align-items: start;
}

.card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: var(--space-md);
  backdrop-filter: blur(16px);
  box-shadow: var(--shadow);
  position: relative;
  overflow: hidden;
}

.card::after {
  content: "";
  position: absolute;
  inset: 0;
  background: linear-gradient(145deg, rgba(255, 255, 255, 0.02), transparent 55%);
  pointer-events: none;
}

.card__header {
  display: flex;
  justify-content: space-between;
  gap: var(--space-sm);
  align-items: flex-start;
  margin-bottom: var(--space-md);
}

.card__subtitle {
  margin: 0.25rem 0 0;
  color: var(--text-muted);
  font-size: 0.95rem;
}

.scoreboard__grid {
  margin: 0;
  display: grid;
  gap: var(--space-sm);
  grid-template-columns: repeat(auto-fit, minmax(120px, 1fr));
}

.scoreboard__item {
  padding: var(--space-sm);
  background: rgba(148, 163, 184, 0.08);
  border-radius: var(--radius-small);
  border: 1px solid rgba(148, 163, 184, 0.18);
}

.scoreboard__item dt {
  font-size: 0.85rem;
  color: var(--text-muted);
  margin: 0 0 0.25rem;
}

.scoreboard__item dd {
  font-size: 1.8rem;
  font-weight: 700;
  margin: 0;
  color: var(--text-invert);
}

.setup__form {
  display: grid;
  gap: var(--space-md);
}

.setup__fieldset {
  margin: 0;
  padding: var(--space-sm);
  border-radius: var(--radius-small);
  border: 1px solid rgba(148, 163, 184, 0.2);
  background: rgba(148, 163, 184, 0.07);
  display: grid;
  gap: var(--space-xs);
}

.setup__fieldset legend {
  padding: 0 var(--space-xs);
  font-weight: 600;
  color: var(--text-invert);
}

.setup__option {
  display: flex;
  align-items: center;
  gap: var(--space-xs);
  font-size: 0.95rem;
  padding: 0.4rem 0.5rem;
  border-radius: var(--radius-tiny);
  transition: background 0.2s ease;
}

.setup__option:hover {
  background: rgba(239, 126, 59, 0.12);
}

.quiz__body {
  display: grid;
  gap: var(--space-sm);
}

.quiz__prompt {
  margin: 0;
  font-size: 1.05rem;
  color: var(--text-invert);
}

.quiz__form {
  display: grid;
  gap: var(--space-sm);
}

.quiz__input {
  border-radius: var(--radius-small);
  border: 1px solid rgba(148, 163, 184, 0.3);
  background: rgba(15, 23, 42, 0.6);
  padding: 0.85rem 1rem;
  color: var(--text-invert);
  font-size: 1rem;
  transition: border-color 0.2s ease, box-shadow 0.2s ease;
}

.quiz__input:focus {
  outline: none;
  border-color: var(--accent);
  box-shadow: 0 0 0 3px rgba(239, 126, 59, 0.25);
}

.quiz__choices {
  display: grid;
  gap: var(--space-xs);
}

.quiz__choice-button {
  border-radius: var(--radius-small);
  padding: 0.8rem 1rem;
  border: 1px solid rgba(148, 163, 184, 0.25);
  background: rgba(148, 163, 184, 0.08);
  color: var(--text-invert);
  text-align: left;
  cursor: pointer;
  font-size: 1rem;
  transition: transform 0.15s ease, background 0.2s ease, border-color 0.2s ease;
}

.quiz__choice-button:hover,
.quiz__choice-button:focus-visible {
  transform: translateY(-1px);
  background: rgba(239, 126, 59, 0.18);
  border-color: rgba(239, 126, 59, 0.4);
}

.quiz__choice-button.is-selected {
  background: rgba(239, 126, 59, 0.25);
  border-color: rgba(239, 126, 59, 0.55);
  box-shadow: 0 12px 30px rgba(239, 126, 59, 0.25);
}

.quiz__actions {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-xs);
}

.quiz__feedback {
  min-height: 1.5rem;
  margin: 0;
  font-weight: 600;
}

.quiz__feedback--correct {
  color: var(--accent);
}

.quiz__feedback--incorrect {
  color: #f87171;
}

.quiz__context {
  border-radius: var(--radius-small);
  border: 1px solid rgba(148, 163, 184, 0.2);
  background: rgba(148, 163, 184, 0.08);
  padding: var(--space-sm);
  display: grid;
  gap: 0.35rem;
}

.quiz__context strong {
  color: var(--text-invert);
}

.history__list {
  list-style: none;
  margin: 0;
  padding: 0;
  display: grid;
  gap: var(--space-xs);
  max-height: 420px;
  overflow-y: auto;
  padding-right: 0.25rem;
}

.history__item {
  padding: var(--space-xs) var(--space-sm);
  background: rgba(148, 163, 184, 0.07);
  border-radius: var(--radius-tiny);
  border: 1px solid rgba(148, 163, 184, 0.15);
  display: grid;
  gap: 0.15rem;
}

.history__item--correct {
  border-color: rgba(59, 130, 246, 0.5);
}

.history__item--incorrect {
  border-color: rgba(248, 113, 113, 0.5);
}

.history__item time {
  font-size: 0.8rem;
  color: var(--text-muted);
}

.timeline {
  display: grid;
  gap: var(--space-sm);
}

.timeline__legend {
  display: flex;
  justify-content: space-between;
  font-size: 0.85rem;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 0.08em;
}

.timeline__list {
  list-style: none;
  margin: 0;
  padding: 0;
  display: grid;
  gap: var(--space-sm);
}

.timeline__entry {
  border-radius: var(--radius-small);
  border: 1px solid rgba(148, 163, 184, 0.18);
  padding: var(--space-sm);
  background: rgba(148, 163, 184, 0.06);
  display: grid;
  gap: 0.35rem;
  position: relative;
}

.timeline__entry::before {
  content: "";
  position: absolute;
  inset: 0;
  border-radius: inherit;
  box-shadow: inset 0 0 0 2px transparent;
  transition: box-shadow 0.2s ease, transform 0.2s ease;
  pointer-events: none;
}

.timeline__entry.is-active::before {
  box-shadow: inset 0 0 0 2px rgba(239, 126, 59, 0.6);
  transform: translateY(-2px);
}

.timeline__range {
  margin: 0;
  font-size: 0.9rem;
  color: var(--text-muted);
}

.timeline__title {
  margin: 0;
  font-size: 1.2rem;
  font-weight: 600;
  color: var(--text-invert);
}

.timeline__events {
  margin: 0;
  padding-left: 1.2rem;
  display: grid;
  gap: 0.25rem;
}

.timeline__events li {
  font-size: 0.95rem;
  color: var(--text);
}

.timeline__events strong {
  color: var(--accent);
}

.period-picker {
  border-radius: var(--radius-small);
  border: 1px solid rgba(148, 163, 184, 0.22);
  background: rgba(15, 23, 42, 0.55);
  padding: var(--space-sm);
  margin-bottom: var(--space-md);
  display: grid;
  gap: var(--space-sm);
}

.period-picker__grid {
  display: grid;
  gap: var(--space-xs);
  grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
}

.period-chip {
  display: flex;
  flex-direction: column;
  align-items: flex-start;
  gap: 0.25rem;
  padding: var(--space-sm);
  border-radius: var(--radius-small);
  border: 1px solid rgba(148, 163, 184, 0.2);
  background: rgba(148, 163, 184, 0.08);
  transition: border-color 0.2s ease, background 0.2s ease;
}

.period-chip input {
  width: 18px;
  height: 18px;
  accent-color: var(--accent);
}

.period-chip span {
  font-weight: 600;
}

.period-chip small {
  color: var(--text-muted);
}

.period-chip.is-active {
  border-color: rgba(239, 126, 59, 0.7);
  background: rgba(239, 126, 59, 0.12);
}

.footer {
  margin-top: auto;
  padding: var(--space-lg);
  text-align: center;
  color: var(--text-muted);
  font-size: 0.9rem;
}

.visually-hidden {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}

@media (max-width: 1140px) {
  .layout {
    grid-template-columns: 1fr;
  }

  .layout__timeline {
    order: 2;
  }
}

@media (max-width: 720px) {
  .hero {
    padding: var(--space-lg) var(--space-sm) var(--space-md);
  }

  .layout {
    width: min(100%, calc(100% - 2 * var(--space-sm)));
  }

  .card {
    padding: var(--space-sm) var(--space-md);
  }

  .quiz__actions {
    flex-direction: column;
    align-items: stretch;
  }
}