: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%;
}

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;
  overflow: hidden;
}

/* ── App Wrapper ── */
#app {
  position: relative;
  width: 100%;
  max-width: 480px;
  height: 100dvh;
  display: flex;
  flex-direction: column;
  background: var(--bg-primary);
  overflow: hidden;
}

/* ── Overlay Screens ── */
.screen {
  position: absolute;
  inset: 0;
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  gap: 24px;
  background: var(--overlay-bg);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  z-index: 100;
  padding: 32px 24px;
  text-align: center;
  transition: opacity 0.25s ease;
}

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

/* ── Title Gradient ── */
.title-gradient {
  font-size: clamp(2.8rem, 14vw, 4.5rem);
  font-weight: 900;
  letter-spacing: -0.03em;
  line-height: 1;
  background: linear-gradient(135deg, #60A5FA 0%, #3B82F6 40%, #818CF8 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.screen-subtitle {
  font-size: 0.95rem;
  color: var(--text-secondary);
  line-height: 1.6;
  max-width: 320px;
}

/* ── High Score Block ── */
.score-block {
  display: flex;
  gap: 32px;
  background: var(--bg-tertiary);
  border: 1px solid var(--border);
  border-radius: 16px;
  padding: 18px 28px;
}

.score-item {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 4px;
}

.score-label {
  font-size: 0.7rem;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 0.08em;
}

.score-value {
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--accent);
}

/* ── Buttons ── */
.btn {
  display: inline-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-family: inherit;
  font-size: 1rem;
  font-weight: 600;
  cursor: pointer;
  transition: background 0.15s ease, transform 0.1s ease;
  user-select: none;
  -webkit-user-select: none;
}

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

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

.btn-primary {
  background: var(--accent);
  border-color: var(--accent);
  color: #fff;
  font-size: 1.1rem;
  padding: 16px 40px;
}

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

.btn-sm {
  padding: 8px 18px;
  font-size: 0.85rem;
  border-radius: 8px;
}

/* ── Game Over Details ── */
.gameover-stats {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 12px;
  width: 100%;
  max-width: 320px;
}

.stat-card {
  background: var(--bg-tertiary);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 14px 16px;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 4px;
}

.stat-card .stat-label {
  font-size: 0.7rem;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 0.08em;
}

.stat-card .stat-value {
  font-size: 1.4rem;
  font-weight: 700;
  color: var(--text-primary);
}

.stat-card.highlight .stat-value {
  color: var(--accent);
}

.new-record-badge {
  font-size: 0.75rem;
  font-weight: 700;
  color: #F59E0B;
  letter-spacing: 0.05em;
  text-transform: uppercase;
}

/* ── Game Header ── */
#game-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 12px 16px;
  background: var(--bg-secondary);
  border-bottom: 1px solid var(--border);
  flex-shrink: 0;
  gap: 8px;
}

.header-stat {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 2px;
  min-width: 52px;
}

.header-stat .label {
  font-size: 0.62rem;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 0.07em;
}

.header-stat .value {
  font-size: 1.05rem;
  font-weight: 700;
  color: var(--text-primary);
}

.header-stat .value.accent {
  color: var(--accent);
}

/* Lives */
#lives-display {
  display: flex;
  gap: 4px;
  align-items: center;
}

.life-icon {
  font-size: 1.1rem;
  transition: transform 0.2s ease, opacity 0.2s ease;
}

.life-icon.lost {
  opacity: 0.2;
  transform: scale(0.8);
}

/* Combo */
#combo-display {
  font-size: 0.85rem;
  font-weight: 700;
  color: #F59E0B;
  min-width: 48px;
  text-align: center;
  transition: transform 0.15s ease;
}

#combo-display.pop {
  transform: scale(1.3);
}

/* Level Badge */
#level-badge {
  background: var(--bg-tertiary);
  border: 1px solid var(--border);
  border-radius: 20px;
  padding: 3px 10px;
  font-size: 0.72rem;
  font-weight: 700;
  color: var(--text-secondary);
  letter-spacing: 0.05em;
}

/* ── Game Board ── */
#game-board {
  flex: 1;
  position: relative;
  background: var(--board-bg);
  overflow: hidden;
}

/* Danger zone line */
#game-board::after {
  content: '';
  position: absolute;
  bottom: 0;
  left: 0;
  right: 0;
  height: 2px;
  background: linear-gradient(90deg, transparent, rgba(239, 68, 68, 0.6), transparent);
  z-index: 2;
}

/* ── Falling Words ── */
.falling-word {
  position: absolute;
  padding: 6px 12px;
  border-radius: 8px;
  background: var(--bg-secondary);
  border: 1px solid var(--border);
  font-size: 0.95rem;
  font-weight: 600;
  color: var(--text-secondary);
  white-space: nowrap;
  pointer-events: none;
  user-select: none;
  -webkit-user-select: none;
  transition: border-color 0.1s ease, background 0.1s ease;
  will-change: transform;
  z-index: 1;
}

.falling-word.active {
  border-color: var(--accent);
  background: rgba(59, 130, 246, 0.12);
  color: var(--text-primary);
  box-shadow: 0 0 10px rgba(59, 130, 246, 0.25);
}

.falling-word .typed-portion {
  color: var(--accent);
}

.falling-word.danger {
  border-color: rgba(239, 68, 68, 0.7);
  background: rgba(239, 68, 68, 0.08);
  color: #FCA5A5;
}

.falling-word.exploding {
  animation: explode 0.35s ease forwards;
  pointer-events: none;
}

@keyframes explode {
  0%   { transform: scale(1);    opacity: 1; }
  40%  { transform: scale(1.35); opacity: 0.8; }
  100% { transform: scale(0);    opacity: 0; }
}

/* ── Input Area ── */
#input-area {
  padding: 12px 16px;
  background: var(--bg-secondary);
  border-top: 1px solid var(--border);
  flex-shrink: 0;
}

#word-input {
  width: 100%;
  padding: 13px 16px;
  border-radius: 12px;
  border: 1.5px solid var(--border);
  background: var(--bg-tertiary);
  color: var(--text-primary);
  font-family: inherit;
  font-size: 1.05rem;
  font-weight: 500;
  outline: none;
  transition: border-color 0.15s ease, box-shadow 0.15s ease;
  caret-color: var(--accent);
}

#word-input::placeholder {
  color: var(--text-muted);
}

#word-input:focus {
  border-color: var(--accent);
  box-shadow: 0 0 0 3px rgba(59, 130, 246, 0.18);
}

#word-input.correct-flash {
  border-color: #22C55E;
  box-shadow: 0 0 0 3px rgba(34, 197, 94, 0.2);
}

#word-input.wrong-shake {
  border-color: #EF4444;
  animation: shake 0.3s ease;
}

@keyframes shake {
  0%, 100% { transform: translateX(0); }
  20%       { transform: translateX(-6px); }
  40%       { transform: translateX(6px); }
  60%       { transform: translateX(-4px); }
  80%       { transform: translateX(4px); }
}

/* ── Score Popup ── */
.score-popup {
  position: absolute;
  font-size: 0.9rem;
  font-weight: 800;
  color: #22C55E;
  pointer-events: none;
  z-index: 10;
  animation: floatUp 0.8s ease forwards;
}

.score-popup.combo-popup {
  color: #F59E0B;
  font-size: 1rem;
}

@keyframes floatUp {
  0%   { opacity: 1;   transform: translateY(0) scale(1); }
  60%  { opacity: 1;   transform: translateY(-28px) scale(1.1); }
  100% { opacity: 0;   transform: translateY(-52px) scale(0.9); }
}

/* ── Life Lost Flash ── */
.board-flash {
  position: absolute;
  inset: 0;
  background: rgba(239, 68, 68, 0.18);
  z-index: 5;
  pointer-events: none;
  animation: flashFade 0.45s ease forwards;
}

@keyframes flashFade {
  0%   { opacity: 1; }
  100% { opacity: 0; }
}

/* ── Pause Button ── */
#pause-btn {
  position: absolute;
  top: 10px;
  right: 12px;
  z-index: 20;
  background: var(--btn-bg);
  border: 1px solid var(--border);
  color: var(--text-secondary);
  border-radius: 8px;
  padding: 6px 10px;
  font-size: 0.8rem;
  cursor: pointer;
  font-family: inherit;
  font-weight: 600;
  transition: background 0.15s ease;
}

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

/* ── How-to-play list ── */
.how-to-play {
  background: var(--bg-tertiary);
  border: 1px solid var(--border);
  border-radius: 14px;
  padding: 16px 20px;
  text-align: left;
  max-width: 320px;
  width: 100%;
}

.how-to-play h3 {
  font-size: 0.75rem;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--text-muted);
  margin-bottom: 10px;
}

.how-to-play ul {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 6px;
}

.how-to-play li {
  font-size: 0.85rem;
  color: var(--text-secondary);
  display: flex;
  align-items: flex-start;
  gap: 8px;
  line-height: 1.4;
}

.how-to-play li::before {
  content: '▸';
  color: var(--accent);
  flex-shrink: 0;
  margin-top: 1px;
}

/* ── Scrollbar ── */
::-webkit-scrollbar {
  width: 4px;
}

::-webkit-scrollbar-track {
  background: transparent;
}

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