:root {
  --bg: #0a0a0f;
  --bg-card: #14141f;
  --bg-elevated: #1a1a2e;
  --text: #e8e8f0;
  --text-dim: #8888a0;
  --accent: #6c5ce7;
  --accent-glow: #a29bfe;
  --success: #00e676;
  --danger: #ff5252;
  --warning: #ffd740;
  --cell-gap: 6px;
  --radius: 12px;
  --radius-sm: 8px;
  --transition: 0.2s ease;
  --nav-height: 60px;

  --c0: #ff5252;
  --c1: #448aff;
  --c2: #69f0ae;
  --c3: #ffd740;
  --c4: #e040fb;
  --c5: #ff6e40;
  --c6: #40c4ff;
  --c7: #b2ff59;
}

html, body {
  height: 100%;
  overflow: hidden;
}

body {
  font-family: 'Segoe UI', system-ui, -apple-system, sans-serif;
  background: var(--bg);
  color: var(--text);
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  min-height: 100dvh;
  user-select: none;
  -webkit-user-select: none;
  -webkit-tap-highlight-color: transparent;
  padding-bottom: var(--nav-height);
}

/* Screens */
.screen {
  display: none;
  flex-direction: column;
  align-items: center;
  width: 100%;
  max-width: 420px;
  padding: 16px;
  gap: 16px;
}

.screen.active {
  display: flex;
}

.screen-scrollable {
  overflow-y: auto;
  max-height: calc(100dvh - var(--nav-height) - 16px);
  justify-content: flex-start;
  padding-bottom: 24px;
}

/* Typography */
.title {
  font-size: 1.6rem;
  font-weight: 800;
  text-align: center;
  background: linear-gradient(135deg, var(--accent-glow), var(--accent));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.subtitle {
  font-size: 0.95rem;
  color: var(--text-dim);
  text-align: center;
}

.section-title {
  font-size: 1rem;
  font-weight: 700;
  color: var(--text);
  margin-bottom: 8px;
}

/* Buttons */
.btn {
  padding: 14px 36px;
  border-radius: var(--radius);
  font-size: 1.1rem;
  font-weight: 700;
  transition: transform var(--transition), box-shadow var(--transition);
  position: relative;
  overflow: hidden;
}

.btn:active {
  transform: scale(0.96);
}

.btn-primary {
  background: linear-gradient(135deg, var(--accent), #7c4dff);
  color: #fff;
  box-shadow: 0 4px 20px rgba(108, 92, 231, 0.4);
}

.btn-primary:hover {
  box-shadow: 0 6px 28px rgba(108, 92, 231, 0.6);
}

.btn-secondary {
  background: var(--bg-elevated);
  color: var(--text);
  border: 1px solid rgba(255,255,255,0.08);
}

/* HUD */
.hud {
  display: flex;
  justify-content: space-between;
  align-items: center;
  width: 100%;
  padding: 8px 4px;
}

.hud-item {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 2px;
}

.hud-label {
  font-size: 0.7rem;
  color: var(--text-dim);
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.hud-value {
  font-size: 1.4rem;
  font-weight: 800;
  font-variant-numeric: tabular-nums;
}

#hud-timer { color: var(--warning); }
#hud-score { color: var(--accent-glow); }
#hud-combo { color: var(--success); }
#hud-round { color: var(--text); }

/* Countdown overlay */
.countdown-overlay {
  position: fixed;
  inset: 0;
  display: none;
  align-items: center;
  justify-content: center;
  background: rgba(10, 10, 15, 0.85);
  z-index: 100;
}

.countdown-overlay.active { display: flex; }

.countdown-number {
  font-size: 6rem;
  font-weight: 900;
  color: var(--accent-glow);
  animation: countPop 0.6s ease-out;
}

/* Mode selector */
.mode-selector {
  width: 100%;
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.mode-tabs {
  display: flex;
  gap: 6px;
  width: 100%;
}

.mode-tab {
  flex: 1;
  padding: 10px;
  text-align: center;
  border-radius: var(--radius-sm);
  font-weight: 600;
  font-size: 0.85rem;
  background: var(--bg-elevated);
  transition: background var(--transition);
  border: 1px solid transparent;
}

.mode-tab.active {
  background: var(--accent);
  color: #fff;
}

.difficulty-selector {
  display: flex;
  gap: 8px;
  width: 100%;
}

.diff-btn {
  flex: 1;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 4px;
  padding: 10px 8px;
  background: var(--bg-elevated);
  border-radius: var(--radius-sm);
  border: 2px solid transparent;
  transition: border-color var(--transition), background var(--transition);
}

.diff-btn.active {
  border-color: var(--accent);
  background: rgba(108, 92, 231, 0.15);
}

.diff-icon {
  font-size: 1.1rem;
  font-weight: 800;
}

.diff-label {
  font-size: 0.75rem;
  color: var(--text-dim);
}

.start-best-score {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 2px;
}

/* Result screen */
.result-card {
  background: var(--bg-card);
  border-radius: var(--radius);
  padding: 20px;
  width: 100%;
  border: 1px solid rgba(255,255,255,0.06);
}

.result-row {
  display: flex;
  justify-content: space-between;
  padding: 8px 0;
  border-bottom: 1px solid rgba(255,255,255,0.04);
}

.result-row:last-child { border-bottom: none; }

.result-label {
  color: var(--text-dim);
  font-size: 0.9rem;
}

.result-value {
  font-weight: 700;
  font-size: 1rem;
}

.result-score {
  font-size: 2.4rem;
  font-weight: 900;
  text-align: center;
  color: var(--accent-glow);
  padding: 8px 0 0;
}

.result-new-best {
  font-size: 0.85rem;
  font-weight: 800;
  color: var(--warning);
  text-align: center;
  animation: pulse 0.6s ease infinite;
}

.result-buttons {
  display: flex;
  gap: 12px;
  width: 100%;
}

.result-buttons .btn {
  flex: 1;
  text-align: center;
}

/* Share buttons */
.share-buttons {
  display: flex;
  gap: 8px;
  width: 100%;
}

.btn-share {
  flex: 1;
  padding: 10px 8px;
  border-radius: var(--radius-sm);
  font-size: 0.8rem;
  font-weight: 600;
  text-align: center;
  transition: transform var(--transition);
}

.btn-share:active { transform: scale(0.95); }

.btn-share-x {
  background: #000;
  color: #fff;
  border: 1px solid rgba(255,255,255,0.15);
}

.btn-share-kakao {
  background: #fee500;
  color: #191919;
}

.btn-share-copy {
  background: var(--bg-elevated);
  color: var(--text);
  border: 1px solid rgba(255,255,255,0.08);
}

/* Nickname input */
.nickname-input {
  background: var(--bg-elevated);
  border: 1px solid rgba(255,255,255,0.1);
  border-radius: var(--radius-sm);
  padding: 10px 14px;
  color: var(--text);
  font-size: 1rem;
  width: 100%;
  text-align: center;
  outline: none;
  transition: border-color var(--transition);
}

.nickname-input:focus { border-color: var(--accent); }

/* Rankings */
.ranking-tabs {
  display: flex;
  gap: 8px;
  width: 100%;
}

.ranking-tab {
  flex: 1;
  padding: 10px;
  text-align: center;
  border-radius: var(--radius-sm);
  font-weight: 600;
  font-size: 0.85rem;
  background: var(--bg-elevated);
  transition: background var(--transition);
}

.ranking-tab.active { background: var(--accent); color: #fff; }

.ranking-list {
  width: 100%;
  max-height: 300px;
  overflow-y: auto;
  scrollbar-width: thin;
  scrollbar-color: var(--bg-elevated) transparent;
}

.ranking-entry {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 10px 8px;
  border-bottom: 1px solid rgba(255,255,255,0.04);
}

.ranking-rank {
  width: 28px;
  text-align: center;
  font-weight: 800;
  color: var(--text-dim);
}

.ranking-rank.top1 { color: #ffd740; }
.ranking-rank.top2 { color: #ccc; }
.ranking-rank.top3 { color: #cd7f32; }

.ranking-name {
  flex: 1;
  font-weight: 600;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.ranking-score { font-weight: 700; color: var(--accent-glow); }

.ranking-me {
  background: rgba(108, 92, 231, 0.1);
  border-radius: var(--radius-sm);
}

/* Stats screen */
.stats-summary {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 10px;
  width: 100%;
}

.stat-card {
  background: var(--bg-card);
  border-radius: var(--radius-sm);
  padding: 16px;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 4px;
  border: 1px solid rgba(255,255,255,0.04);
}

.stat-number {
  font-size: 1.6rem;
  font-weight: 800;
  color: var(--accent-glow);
  font-variant-numeric: tabular-nums;
}

.stat-desc {
  font-size: 0.75rem;
  color: var(--text-dim);
}

.stats-chart-section, .stats-history {
  width: 100%;
}

.chart-container {
  background: var(--bg-card);
  border-radius: var(--radius-sm);
  padding: 16px 12px;
  border: 1px solid rgba(255,255,255,0.04);
  overflow: hidden;
}

.chart-container canvas {
  width: 100% !important;
  height: auto !important;
}

.history-list {
  display: flex;
  flex-direction: column;
  gap: 4px;
  max-height: 200px;
  overflow-y: auto;
}

.history-item {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 10px 12px;
  background: var(--bg-card);
  border-radius: var(--radius-sm);
  font-size: 0.85rem;
  border: 1px solid rgba(255,255,255,0.04);
}

.history-score { font-weight: 700; color: var(--accent-glow); }
.history-meta { color: var(--text-dim); font-size: 0.75rem; }

/* Guide screen */
.guide-card {
  background: var(--bg-card);
  border-radius: var(--radius);
  padding: 20px;
  width: 100%;
  border: 1px solid rgba(255,255,255,0.06);
}

.guide-heading {
  font-size: 1rem;
  font-weight: 700;
  margin-bottom: 12px;
  color: var(--accent-glow);
}

.guide-list {
  display: flex;
  flex-direction: column;
  gap: 8px;
  padding-left: 16px;
}

.guide-list li {
  list-style: disc;
  font-size: 0.9rem;
  color: var(--text);
  line-height: 1.6;
}

.guide-tips li {
  list-style: none;
  padding-left: 0;
  margin-left: -16px;
}

.guide-formula {
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.formula-row {
  display: flex;
  justify-content: space-between;
  padding: 6px 0;
  font-size: 0.9rem;
}

.formula-label { color: var(--text-dim); }
.formula-value { font-weight: 600; }

.guide-difficulty-grid {
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.guide-diff-item {
  display: flex;
  flex-direction: column;
  gap: 4px;
}

.guide-diff-item p {
  font-size: 0.85rem;
  color: var(--text-dim);
  line-height: 1.5;
}

.guide-diff-badge {
  display: inline-block;
  padding: 4px 10px;
  border-radius: 4px;
  font-size: 0.8rem;
  font-weight: 700;
  width: fit-content;
}

.guide-diff-badge.easy { background: rgba(105, 240, 174, 0.15); color: var(--success); }
.guide-diff-badge.normal { background: rgba(108, 92, 231, 0.15); color: var(--accent-glow); }
.guide-diff-badge.hard { background: rgba(255, 82, 82, 0.15); color: var(--danger); }

/* About / FAQ */
.about-section {
  width: 100%;
}

.about-text {
  font-size: 0.95rem;
  line-height: 1.7;
  color: var(--text);
  margin-bottom: 12px;
}

.faq-section {
  width: 100%;
}

.faq-item {
  background: var(--bg-card);
  border-radius: var(--radius-sm);
  margin-bottom: 8px;
  border: 1px solid rgba(255,255,255,0.06);
  overflow: hidden;
}

.faq-q {
  padding: 14px 16px;
  font-weight: 600;
  font-size: 0.9rem;
  cursor: pointer;
  list-style: none;
}

.faq-q::-webkit-details-marker { display: none; }

.faq-q::before {
  content: '+ ';
  color: var(--accent-glow);
  font-weight: 800;
}

.faq-item[open] .faq-q::before {
  content: '- ';
}

.faq-a {
  padding: 0 16px 14px;
  font-size: 0.85rem;
  color: var(--text-dim);
  line-height: 1.6;
}

/* Bottom navigation */
.bottom-nav {
  position: fixed;
  bottom: 0;
  left: 0;
  right: 0;
  height: var(--nav-height);
  background: var(--bg-card);
  border-top: 1px solid rgba(255,255,255,0.06);
  display: flex;
  justify-content: space-around;
  align-items: center;
  z-index: 50;
  padding-bottom: env(safe-area-inset-bottom, 0);
}

.bottom-nav.hidden { display: none; }

.nav-item {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 3px;
  padding: 6px 12px;
  color: var(--text-dim);
  font-size: 0.65rem;
  transition: color var(--transition);
}

.nav-item.active { color: var(--accent-glow); }

.nav-icon {
  width: 22px;
  height: 22px;
}

/* Toast */
.toast {
  position: fixed;
  bottom: calc(var(--nav-height) + 16px);
  left: 50%;
  transform: translateX(-50%) translateY(20px);
  background: var(--bg-elevated);
  color: var(--text);
  padding: 10px 20px;
  border-radius: var(--radius);
  font-size: 0.85rem;
  font-weight: 600;
  opacity: 0;
  pointer-events: none;
  transition: opacity 0.3s ease, transform 0.3s ease;
  z-index: 200;
  border: 1px solid rgba(255,255,255,0.1);
}

.toast.show {
  opacity: 1;
  transform: translateX(-50%) translateY(0);
}

/* Ad placeholders */
.ad-slot {
  width: 100%;
  min-height: 60px;
  background: var(--bg-card);
  border-radius: var(--radius-sm);
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--text-dim);
  font-size: 0.75rem;
  border: 1px dashed rgba(255,255,255,0.08);
}

/* Responsive */
@media (max-width: 360px) {
  .title { font-size: 1.3rem; }
  .hud-value { font-size: 1.1rem; }
  .btn { padding: 12px 24px; font-size: 1rem; }
}

@media (min-height: 800px) {
  .screen { gap: 20px; }
}

@keyframes countPop {
  0% { transform: scale(0.3); opacity: 0; }
  60% { transform: scale(1.1); opacity: 1; }
  100% { transform: scale(1); }
}