:root {
  --bg: #0f172a;
  --bg-card: #1e293b;
  --bg-elevated: #273549;
  --bg-input: #0b1120;
  --text: #f8fafc;
  --text-muted: #94a3b8;
  --accent: #38bdf8;
  --accent-strong: #0284c7;
  --success: #22c55e;
  --success-bg: rgba(34, 197, 94, 0.14);
  --warning: #f59e0b;
  --warning-bg: rgba(245, 158, 11, 0.14);
  --danger: #ef4444;
  --danger-bg: rgba(239, 68, 68, 0.14);
  --purple: #a855f7;
  --purple-bg: rgba(168, 85, 247, 0.14);
  --border: #334155;
  --radius: 14px;
  --shadow: 0 10px 25px -5px rgba(0, 0, 0, 0.35);
}

[data-theme="light"] {
  --bg: #f1f5f9;
  --bg-card: #ffffff;
  --bg-elevated: #f8fafc;
  --bg-input: #f1f5f9;
  --text: #0f172a;
  --text-muted: #475569;
  --accent: #0284c7;
  --accent-strong: #0369a1;
  --border: #cbd5e1;
  --shadow: 0 8px 20px -4px rgba(15, 23, 42, 0.08);
}

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

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Inter, sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.55;
  min-height: 100vh;
}

.topbar {
  position: sticky;
  top: 0;
  z-index: 50;
  background: rgba(15, 23, 42, 0.92);
  backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--border);
  padding: 12px 24px;
}

[data-theme="light"] .topbar {
  background: rgba(255, 255, 255, 0.92);
}

.topbar-inner {
  max-width: 1320px;
  margin: 0 auto;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  flex-wrap: wrap;
}

.brand {
  display: flex;
  align-items: center;
  gap: 12px;
}

.brand-badge {
  width: 42px;
  height: 42px;
  border-radius: 11px;
  background: linear-gradient(135deg, #0284c7, #38bdf8);
  color: #fff;
  font-weight: 800;
  font-size: 19px;
  display: flex;
  align-items: center;
  justify-content: center;
  box-shadow: 0 4px 12px rgba(56, 189, 248, 0.35);
}

.brand-title {
  font-size: 17px;
  font-weight: 700;
  letter-spacing: -0.01em;
}

.brand-sub {
  font-size: 12px;
  color: var(--text-muted);
}

.stats-bar {
  display: flex;
  align-items: center;
  gap: 10px;
  flex-wrap: wrap;
}

.stat-pill {
  background: var(--bg-card);
  border: 1px solid var(--border);
  padding: 6px 12px;
  border-radius: 999px;
  font-size: 13px;
  font-weight: 600;
  display: flex;
  align-items: center;
  gap: 6px;
}

.stat-pill span.val {
  color: var(--accent);
  font-weight: 700;
}

.nav-tabs {
  max-width: 1320px;
  margin: 18px auto 0;
  padding: 0 24px;
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
}

.nav-tab {
  background: var(--bg-card);
  color: var(--text-muted);
  border: 1px solid var(--border);
  padding: 11px 16px;
  border-radius: 11px;
  font-size: 14px;
  font-weight: 600;
  cursor: pointer;
  transition: all 0.16s ease;
  display: flex;
  align-items: center;
  gap: 8px;
}

.nav-tab:hover {
  color: var(--text);
  border-color: var(--accent);
}

.nav-tab.active {
  background: linear-gradient(135deg, #0284c7, #0ea5e9);
  color: #ffffff;
  border-color: transparent;
  box-shadow: 0 4px 14px rgba(14, 165, 233, 0.32);
}

.container {
  max-width: 1320px;
  margin: 20px auto 60px;
  padding: 0 24px;
}

.tab-panel {
  display: none;
}

.tab-panel.active {
  display: block;
}

.hero-banner {
  background: linear-gradient(135deg, rgba(2, 132, 199, 0.18), rgba(168, 85, 247, 0.14));
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 20px 24px;
  margin-bottom: 20px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 20px;
  flex-wrap: wrap;
}

.hero-banner h1 {
  font-size: 20px;
  margin-bottom: 6px;
}

.hero-banner p {
  color: var(--text-muted);
  font-size: 14px;
  max-width: 780px;
}

.grid-2 {
  display: grid;
  grid-template-columns: 330px 1fr;
  gap: 20px;
  align-items: start;
}

.grid-equal {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(340px, 1fr));
  gap: 20px;
}

@media (max-width: 940px) {
  .grid-2 {
    grid-template-columns: 1fr;
  }
}

.card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 20px;
  box-shadow: var(--shadow);
}

.card-title {
  font-size: 16px;
  font-weight: 700;
  margin-bottom: 12px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 8px;
}

.cat-list {
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.cat-btn {
  text-align: left;
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  color: var(--text);
  padding: 12px 14px;
  border-radius: 10px;
  cursor: pointer;
  transition: all 0.15s ease;
}

.cat-btn:hover {
  border-color: var(--accent);
}

.cat-btn.active {
  border-color: var(--accent);
  background: rgba(56, 189, 248, 0.14);
}

.cat-btn-title {
  font-size: 14px;
  font-weight: 700;
  margin-bottom: 3px;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.cat-btn-desc {
  font-size: 12px;
  color: var(--text-muted);
}

.badge {
  display: inline-flex;
  align-items: center;
  gap: 4px;
  padding: 3px 9px;
  border-radius: 999px;
  font-size: 11px;
  font-weight: 700;
}

.badge-blue {
  background: rgba(56, 189, 248, 0.16);
  color: var(--accent);
}

.badge-green {
  background: var(--success-bg);
  color: var(--success);
}

.badge-amber {
  background: var(--warning-bg);
  color: var(--warning);
}

.badge-purple {
  background: var(--purple-bg);
  color: var(--purple);
}

.timer-box {
  display: flex;
  align-items: center;
  gap: 14px;
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  padding: 10px 16px;
  border-radius: 12px;
}

.timer-readout {
  font-family: "SF Mono", Menlo, Consolas, monospace;
  font-size: 22px;
  font-weight: 800;
  color: var(--accent);
}

.timer-readout.warn {
  color: var(--warning);
}

.timer-readout.over {
  color: var(--danger);
}

.pace-bar-wrap {
  width: 100%;
  height: 8px;
  background: var(--bg-input);
  border-radius: 999px;
  overflow: hidden;
  margin: 12px 0 18px;
}

.pace-bar-fill {
  height: 100%;
  background: var(--success);
  width: 0%;
  transition: width 0.25s linear, background-color 0.25s ease;
}

.question-box {
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 20px;
  margin-bottom: 16px;
}

.question-meta {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 10px;
  margin-bottom: 10px;
  flex-wrap: wrap;
}

.question-text {
  font-size: 18px;
  font-weight: 600;
  line-height: 1.6;
}

.math-expr {
  font-family: "Cambria Math", "Times New Roman", Georgia, serif;
  font-size: 1.12em;
  background: rgba(56, 189, 248, 0.09);
  padding: 2px 7px;
  border-radius: 6px;
  display: inline-block;
  margin: 2px 0;
}

.frac {
  display: inline-flex;
  flex-direction: column;
  vertical-align: middle;
  text-align: center;
  padding: 0 4px;
  font-size: 0.92em;
}

.frac > span:first-child {
  border-bottom: 1.5px solid currentColor;
  padding: 0 3px 1px;
}

.frac > span:last-child {
  padding: 1px 3px 0;
}

.options-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(210px, 1fr));
  gap: 10px;
  margin-top: 16px;
}

.option-btn {
  background: var(--bg-card);
  border: 2px solid var(--border);
  color: var(--text);
  padding: 14px 16px;
  border-radius: 11px;
  font-size: 16px;
  font-weight: 600;
  cursor: pointer;
  text-align: left;
  transition: all 0.14s ease;
  display: flex;
  align-items: center;
  gap: 10px;
}

.option-btn:hover:not(:disabled) {
  border-color: var(--accent);
  transform: translateY(-1px);
}

.option-btn.correct {
  border-color: var(--success);
  background: var(--success-bg);
}

.option-btn.wrong {
  border-color: var(--danger);
  background: var(--danger-bg);
}

.option-key {
  width: 28px;
  height: 28px;
  border-radius: 7px;
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  display: inline-flex;
  align-items: center;
  justify-content: center;
  font-size: 13px;
  font-weight: 700;
  flex-shrink: 0;
}

.shortcut-box {
  background: linear-gradient(135deg, rgba(245, 158, 11, 0.14), rgba(56, 189, 248, 0.1));
  border-left: 4px solid var(--warning);
  border-radius: 10px;
  padding: 14px 16px;
  margin-top: 14px;
  font-size: 14px;
}

.shortcut-box strong {
  color: var(--warning);
  display: block;
  margin-bottom: 4px;
  font-size: 14px;
}

.trap-box {
  background: var(--danger-bg);
  border-left: 4px solid var(--danger);
  border-radius: 10px;
  padding: 12px 16px;
  margin-top: 10px;
  font-size: 13.5px;
}

.trap-box strong {
  color: var(--danger);
  display: block;
  margin-bottom: 3px;
}

.step-card {
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  border-radius: 11px;
  padding: 16px;
  margin-bottom: 12px;
  transition: all 0.2s ease;
}

.step-card.locked {
  opacity: 0.45;
  pointer-events: none;
}

.step-card.completed {
  border-color: var(--success);
}

.step-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 8px;
  font-weight: 700;
  font-size: 14px;
}

.btn {
  background: var(--accent-strong);
  color: #fff;
  border: none;
  padding: 10px 16px;
  border-radius: 9px;
  font-size: 14px;
  font-weight: 600;
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  gap: 7px;
  transition: all 0.15s ease;
}

.btn:hover {
  filter: brightness(1.1);
}

.btn-secondary {
  background: var(--bg-elevated);
  color: var(--text);
  border: 1px solid var(--border);
}

.btn-secondary:hover {
  border-color: var(--accent);
}

.btn-warning {
  background: var(--warning);
  color: #0f172a;
}

.btn-success {
  background: var(--success);
  color: #052e16;
}

.input-field {
  background: var(--bg-input);
  border: 1px solid var(--border);
  color: var(--text);
  padding: 10px 14px;
  border-radius: 9px;
  font-size: 15px;
  width: 100%;
}

.input-field:focus {
  outline: none;
  border-color: var(--accent);
}

/* Modal podglądu strony podręcznika */
.modal-backdrop {
  position: fixed;
  inset: 0;
  background: rgba(2, 6, 23, 0.82);
  backdrop-filter: blur(6px);
  z-index: 200;
  display: none;
  align-items: center;
  justify-content: center;
  padding: 20px;
}

.modal-backdrop.open {
  display: flex;
}

.modal-content {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 16px;
  max-width: 960px;
  width: 100%;
  max-height: 92vh;
  display: flex;
  flex-direction: column;
  overflow: hidden;
  box-shadow: 0 25px 50px -12px rgba(0, 0, 0, 0.65);
}

.modal-header {
  padding: 14px 20px;
  border-bottom: 1px solid var(--border);
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
}

.modal-body {
  padding: 16px;
  overflow-y: auto;
  text-align: center;
}

.modal-body img {
  max-width: 100%;
  height: auto;
  border-radius: 8px;
  border: 1px solid var(--border);
}

/* Galeria stron podręcznika */
.pages-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(230px, 1fr));
  gap: 14px;
}

.page-card {
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  border-radius: 11px;
  padding: 14px;
  cursor: pointer;
  transition: all 0.15s ease;
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  gap: 10px;
}

.page-card:hover {
  border-color: var(--accent);
  transform: translateY(-2px);
}

.number-line-svg {
  width: 100%;
  height: 150px;
  background: var(--bg-input);
  border: 1px solid var(--border);
  border-radius: 10px;
  margin: 12px 0;
}

.cheat-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(360px, 1fr));
  gap: 16px;
}

.cheat-card {
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 16px;
}

.cheat-card h3 {
  font-size: 15px;
  color: var(--accent);
  margin-bottom: 8px;
}

.vs-row {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 10px;
  margin-top: 10px;
  font-size: 13px;
}

.vs-slow {
  background: var(--danger-bg);
  border: 1px solid rgba(239, 68, 68, 0.3);
  padding: 10px;
  border-radius: 8px;
}

.vs-fast {
  background: var(--success-bg);
  border: 1px solid rgba(34, 197, 94, 0.3);
  padding: 10px;
  border-radius: 8px;
}