:root {
  --bg-primary: #0D1117;
  --bg-secondary: #161B22;
  --bg-tertiary: #21262D;
  --text-primary: #F0F6FC;
  --text-secondary: #8B949E;
  --text-muted: #484F58;
  --accent: #3B82F6;
  --border: #30363D;
  --btn-bg: #21262D;
  --btn-active: #30363D;
  --overlay-bg: rgba(0, 0, 0, 0.85);
  --board-bg: #0A0E14;
}

@media (prefers-color-scheme: light) {
  :root {
    --bg-primary: #FFFFFF;
    --bg-secondary: #F6F8FA;
    --bg-tertiary: #E9ECF0;
    --text-primary: #1B1E28;
    --text-secondary: #57606A;
    --text-muted: #8C959F;
    --accent: #3182F6;
    --border: #D0D7DE;
    --btn-bg: #E9ECF0;
    --btn-active: #D0D7DE;
    --overlay-bg: rgba(255, 255, 255, 0.9);
    --board-bg: #F0F2F5;
  }
}

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

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

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Pretendard', 'Segoe UI', Roboto, sans-serif;
  background: var(--bg-primary);
  color: var(--text-primary);
  display: flex;
  justify-content: center;
  align-items: center;
  min-height: 100dvh;
}

/* ─── App Shell ─────────────────────────────────────── */
#app {
  position: relative;
  width: 100%;
  max-width: 480px;
  height: 100dvh;
  overflow: hidden;
  background: var(--bg-secondary);
  border-left: 1px solid var(--border);
  border-right: 1px solid var(--border);
}

/* ─── Overlay Screens ────────────────────────────────── */
.screen {
  position: absolute;
  inset: 0;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  background: var(--overlay-bg);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  z-index: 100;
  padding: 24px;
  gap: 20px;
  transition: opacity 0.25s ease, visibility 0.25s ease;
}

.screen.hidden {
  opacity: 0;
  visibility: hidden;
  pointer-events: none;
}

/* ─── Title ──────────────────────────────────────────── */
.game-title {
  font-size: 56px;
  font-weight: 800;
  letter-spacing: -2px;
  background: linear-gradient(135deg, var(--accent) 0%, #a78bfa 50%, #ec4899 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  line-height: 1;
  text-align: center;
}

.game-subtitle {
  font-size: 14px;
  color: var(--text-secondary);
  letter-spacing: 0.05em;
  text-align: center;
}

/* ─── Buttons ────────────────────────────────────────── */
.btn {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 14px 32px;
  border-radius: 12px;
  border: 1px solid var(--border);
  background: var(--btn-bg);
  color: var(--text-primary);
  font-size: 16px;
  font-weight: 600;
  font-family: inherit;
  cursor: pointer;
  transition: background 0.15s, transform 0.1s, border-color 0.15s;
  min-width: 200px;
  width: 100%;
  max-width: 320px;
  user-select: none;
  -webkit-user-select: none;
  touch-action: manipulation;
}

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

.btn:active {
  transform: scale(0.97);
}

.btn-primary {
  background: var(--accent);
  border-color: var(--accent);
  color: #fff;
}

.btn-primary:hover {
  background: #2563eb;
  border-color: #2563eb;
}

.btn-danger {
  border-color: #ef4444;
  color: #ef4444;
}

.btn-danger:hover {
  background: rgba(239, 68, 68, 0.1);
}

/* ─── Song Selector ─────────────────────────────────── */
.song-list {
  display: flex;
  flex-direction: column;
  gap: 10px;
  width: 100%;
  max-width: 340px;
  max-height: 320px;
  overflow-y: auto;
  padding-right: 4px;
}

.song-list::-webkit-scrollbar {
  width: 4px;
}

.song-list::-webkit-scrollbar-track {
  background: var(--bg-tertiary);
  border-radius: 2px;
}

.song-list::-webkit-scrollbar-thumb {
  background: var(--border);
  border-radius: 2px;
}

.song-card {
  display: flex;
  align-items: center;
  gap: 14px;
  padding: 14px 16px;
  border-radius: 12px;
  border: 2px solid var(--border);
  background: var(--btn-bg);
  cursor: pointer;
  transition: border-color 0.15s, background 0.15s, transform 0.1s;
  user-select: none;
  -webkit-user-select: none;
  touch-action: manipulation;
}

.song-card:hover {
  border-color: var(--accent);
  background: var(--btn-active);
}

.song-card:active {
  transform: scale(0.98);
}

.song-card.selected {
  border-color: var(--accent);
  background: rgba(59, 130, 246, 0.1);
}

.song-icon {
  font-size: 28px;
  line-height: 1;
  flex-shrink: 0;
}

.song-info {
  flex: 1;
  min-width: 0;
}

.song-name {
  font-size: 15px;
  font-weight: 700;
  color: var(--text-primary);
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.song-meta {
  font-size: 12px;
  color: var(--text-secondary);
  margin-top: 2px;
}

.song-best {
  font-size: 11px;
  color: var(--accent);
  margin-top: 3px;
  font-weight: 600;
}

.difficulty-badge {
  font-size: 10px;
  font-weight: 700;
  padding: 3px 8px;
  border-radius: 20px;
  flex-shrink: 0;
  letter-spacing: 0.04em;
}

.diff-easy   { background: rgba(34, 197, 94, 0.2);  color: #22c55e; }
.diff-normal { background: rgba(234, 179, 8, 0.2);   color: #eab308; }
.diff-hard   { background: rgba(239, 68, 68, 0.2);   color: #ef4444; }
.diff-expert { background: rgba(168, 85, 247, 0.2);  color: #a855f7; }

/* ─── Result Screen ──────────────────────────────────── */
.result-title {
  font-size: 28px;
  font-weight: 800;
  background: linear-gradient(135deg, var(--accent), #a78bfa);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.result-score-block {
  text-align: center;
  background: var(--bg-tertiary);
  border: 1px solid var(--border);
  border-radius: 16px;
  padding: 20px 32px;
  width: 100%;
  max-width: 320px;
}

.result-score-label {
  font-size: 12px;
  color: var(--text-secondary);
  letter-spacing: 0.1em;
  text-transform: uppercase;
  margin-bottom: 4px;
}

.result-score-value {
  font-size: 48px;
  font-weight: 800;
  color: var(--text-primary);
  line-height: 1;
}

.result-new-best {
  font-size: 12px;
  color: #f59e0b;
  font-weight: 700;
  margin-top: 6px;
  letter-spacing: 0.05em;
}

.result-stats {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 8px;
  width: 100%;
  max-width: 320px;
}

.result-stat {
  text-align: center;
  background: var(--bg-tertiary);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 10px 6px;
}

.result-stat-count {
  font-size: 20px;
  font-weight: 800;
  line-height: 1;
}

.result-stat-label {
  font-size: 10px;
  color: var(--text-secondary);
  margin-top: 3px;
  font-weight: 600;
}

.grade-perfect { color: #3b82f6; }
.grade-great   { color: #22c55e; }
.grade-good    { color: #eab308; }
.grade-miss    { color: #ef4444; }

/* ─── Game HUD ───────────────────────────────────────── */
#game-hud {
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 10px 14px 8px;
  background: var(--bg-secondary);
  border-bottom: 1px solid var(--border);
  z-index: 10;
  gap: 10px;
}

#hud-combo {
  display: flex;
  flex-direction: column;
  align-items: center;
  min-width: 60px;
}

#combo-value {
  font-size: 26px;
  font-weight: 800;
  color: var(--accent);
  line-height: 1;
  transition: transform 0.1s;
}

#combo-value.bump {
  transform: scale(1.3);
}

#combo-label {
  font-size: 9px;
  color: var(--text-muted);
  letter-spacing: 0.1em;
  text-transform: uppercase;
  font-weight: 700;
}

#hud-center {
  flex: 1;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 6px;
  min-width: 0;
}

#hud-song-name {
  font-size: 12px;
  font-weight: 700;
  color: var(--text-secondary);
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
  max-width: 140px;
}

#health-bar-track {
  width: 100%;
  max-width: 160px;
  height: 6px;
  background: var(--bg-tertiary);
  border-radius: 3px;
  overflow: hidden;
}

#health-bar-fill {
  height: 100%;
  border-radius: 3px;
  background: linear-gradient(90deg, #22c55e, #86efac);
  transition: width 0.2s ease, background 0.3s;
}

#health-bar-fill.low {
  background: linear-gradient(90deg, #ef4444, #fca5a5);
}

#hud-score {
  display: flex;
  flex-direction: column;
  align-items: flex-end;
  min-width: 60px;
}

#score-value {
  font-size: 18px;
  font-weight: 800;
  color: var(--text-primary);
  line-height: 1;
}

#score-label {
  font-size: 9px;
  color: var(--text-muted);
  letter-spacing: 0.1em;
  text-transform: uppercase;
  font-weight: 700;
}

/* ─── Pause Button ───────────────────────────────────── */
#btn-pause {
  position: absolute;
  top: 10px;
  right: 14px;
  z-index: 20;
  display: none;
  width: 36px;
  height: 36px;
  border-radius: 8px;
  border: 1px solid var(--border);
  background: var(--btn-bg);
  color: var(--text-secondary);
  font-size: 16px;
  cursor: pointer;
  align-items: center;
  justify-content: center;
  transition: background 0.15s;
  touch-action: manipulation;
}

#btn-pause:hover {
  background: var(--btn-active);
}

/* ─── Game Board ─────────────────────────────────────── */
#game-board {
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: var(--board-bg);
}

/* ─── Canvas ─────────────────────────────────────────── */
#game-canvas {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  touch-action: none;
}

/* ─── Hit Feedback ───────────────────────────────────── */
.hit-feedback {
  position: absolute;
  font-size: 18px;
  font-weight: 800;
  pointer-events: none;
  animation: feedbackFloat 0.65s ease-out forwards;
  z-index: 20;
  letter-spacing: 0.04em;
  text-shadow: 0 2px 8px rgba(0,0,0,0.5);
}

@keyframes feedbackFloat {
  0%   { opacity: 1; transform: translateY(0) scale(1); }
  30%  { transform: translateY(-14px) scale(1.15); }
  100% { opacity: 0; transform: translateY(-36px) scale(0.9); }
}

/* ─── Countdown ──────────────────────────────────────── */
#countdown {
  position: absolute;
  inset: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 96px;
  font-weight: 900;
  color: var(--accent);
  background: var(--overlay-bg);
  backdrop-filter: blur(8px);
  -webkit-backdrop-filter: blur(8px);
  z-index: 90;
  pointer-events: none;
  opacity: 0;
  transition: opacity 0.15s;
}

#countdown.visible {
  opacity: 1;
}

/* ─── Section Labels ─────────────────────────────────── */
.section-label {
  font-size: 12px;
  font-weight: 700;
  color: var(--text-muted);
  letter-spacing: 0.12em;
  text-transform: uppercase;
  align-self: flex-start;
  width: 100%;
  max-width: 340px;
  padding-left: 2px;
  margin-bottom: -8px;
}

/* ─── Pause Screen specifics ─────────────────────────── */
#screen-pause .pause-info {
  font-size: 14px;
  color: var(--text-secondary);
  text-align: center;
  line-height: 1.5;
}

#screen-pause .pause-score {
  font-size: 32px;
  font-weight: 800;
  color: var(--text-primary);
}

/* ─── Touch indicator flash ──────────────────────────── */
.lane-flash {
  position: absolute;
  bottom: 0;
  width: 25%;
  pointer-events: none;
  animation: laneFlash 0.15s ease-out forwards;
  z-index: 5;
}

@keyframes laneFlash {
  0%   { opacity: 0.45; }
  100% { opacity: 0; }
}

/* ─── Responsive ─────────────────────────────────────── */
@media (max-width: 400px) {
  .game-title { font-size: 44px; }
  .result-score-value { font-size: 40px; }
}