:root {
  color-scheme: dark;
  --bg: #020617;
  --panel: #0f172a;
  --panel-soft: #111827;
  --border: #1e293b;
  --text: #e2e8f0;
  --muted: #94a3b8;
  --accent: #38bdf8;
  --accent-soft: rgba(56, 189, 248, 0.16);
  --success: #86efac;
  --success-bg: #052e16;
  --danger: #fecaca;
  --danger-bg: #450a0a;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: Inter, Segoe UI, Roboto, Arial, sans-serif;
  background: radial-gradient(circle at top, #0f172a 0%, var(--bg) 60%);
  color: var(--text);
}

.container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 24px;
}

.hero {
  display: grid;
  gap: 12px;
  margin-bottom: 24px;
}

.badge {
  width: fit-content;
  padding: 6px 10px;
  border-radius: 999px;
  background: var(--accent-soft);
  color: #bae6fd;
  font-size: 0.82rem;
  border: 1px solid rgba(56, 189, 248, 0.25);
}

h1, h2, h3, p {
  margin: 0;
}

.hero-copy {
  max-width: 760px;
  color: var(--muted);
  line-height: 1.55;
}

.layout {
  display: grid;
  grid-template-columns: 320px 1fr;
  gap: 20px;
  align-items: start;
}

.card {
  background: rgba(15, 23, 42, 0.88);
  border: 1px solid var(--border);
  border-radius: 18px;
  padding: 18px;
  box-shadow: 0 20px 40px rgba(2, 6, 23, 0.25);
}

.stack {
  display: grid;
  gap: 16px;
}

.paper-grid {
  display: grid;
  gap: 10px;
}

.paper-btn,
.option-btn,
.btn,
.select {
  border: 1px solid #334155;
  background: #0b1220;
  color: var(--text);
  border-radius: 12px;
  font: inherit;
}

.paper-btn {
  text-align: left;
  padding: 14px;
  cursor: pointer;
}

.paper-btn.active {
  border-color: var(--accent);
  background: rgba(14, 165, 233, 0.12);
}

.paper-btn small {
  display: block;
  color: var(--muted);
  margin-top: 6px;
}

.study-path {
  display: grid;
  gap: 10px;
}

.materials-section {
  display: grid;
  gap: 10px;
  padding: 12px;
  border-radius: 12px;
  background: rgba(15, 23, 42, 0.72);
  border: 1px solid #1f2937;
}

.materials-list {
  margin: 0;
  padding-left: 18px;
  color: var(--muted);
  display: grid;
  gap: 8px;
}

.path-item {
  display: flex;
  gap: 10px;
  align-items: flex-start;
  padding: 10px 12px;
  border-radius: 12px;
  background: rgba(15, 23, 42, 0.75);
  border: 1px solid #1f2937;
}

.path-item input {
  margin-top: 3px;
}

.meta,
.small {
  color: var(--muted);
  font-size: 0.92rem;
}

.toolbar {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 12px;
  margin: 16px 0;
  align-items: center;
}

.select,
.btn {
  padding: 10px 12px;
  height: 48px;
  width: 100%;
  line-height: 1.2;
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  white-space: nowrap;
}

.select {
  display: block;
  appearance: none;
  -webkit-appearance: none;
  background-color: #0b1220;
}

.btn:hover,
.option-btn:hover,
.paper-btn:hover {
  border-color: var(--accent);
}

.quiz-header {
  display: flex;
  justify-content: space-between;
  gap: 12px;
  align-items: flex-start;
  margin-bottom: 0;
}

.statline {
  display: flex;
  gap: 10px;
  flex-wrap: wrap;
}

.pill {
  padding: 6px 10px;
  border-radius: 999px;
  background: rgba(148, 163, 184, 0.12);
  border: 1px solid rgba(148, 163, 184, 0.2);
  color: #cbd5e1;
  font-size: 0.84rem;
}

.question-card {
  padding: 18px;
  border-radius: 16px;
  background: #020817;
  border: 1px solid var(--border);
}

.question-title {
  font-size: 1.08rem;
  line-height: 1.5;
  margin-bottom: 14px;
}

.options {
  display: grid;
  gap: 10px;
}

.option-btn {
  text-align: left;
  padding: 12px 14px;
  cursor: pointer;
}

.option-btn.correct-choice {
  border-color: #22c55e;
  background: rgba(34, 197, 94, 0.12);
}

.option-btn.wrong-choice {
  border-color: #ef4444;
  background: rgba(239, 68, 68, 0.12);
}

.option-btn:disabled {
  opacity: 0.95;
  cursor: not-allowed;
}

.feedback {
  margin-top: 14px;
  padding: 14px;
  border-radius: 14px;
  line-height: 1.5;
}

.feedback.correct {
  background: var(--success-bg);
  border: 1px solid #166534;
  color: var(--success);
}

.feedback.incorrect {
  background: var(--danger-bg);
  border: 1px solid #991b1b;
  color: var(--danger);
}

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

.empty-state {
  padding: 22px;
  border-radius: 16px;
  border: 1px dashed #334155;
  color: var(--muted);
  background: rgba(15, 23, 42, 0.45);
}

@media (max-width: 960px) {
  .layout {
    grid-template-columns: 1fr;
  }
}

@media (max-width: 640px) {
  .toolbar {
    grid-template-columns: 1fr;
  }

  .quiz-header {
    flex-direction: column;
  }
}