:root {
  /* Nike-inspired: jet black + volt green */
  --bg-1: #000000;
  --bg-2: #0a0a0a;
  --bg-3: #141414;
  --text: #ffffff;
  --text-dim: #8a8a8a;
  --accent: #DCFF1A;       /* Nike "Volt" */
  --accent-2: #ffffff;
  --correct: #DCFF1A;
  --wrong: #FF2D2D;
  --card-bg: rgba(255, 255, 255, 0.04);
  --card-border: rgba(255, 255, 255, 0.10);
}

* { box-sizing: border-box; margin: 0; padding: 0; }
html, body { height: 100%; }
body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  background: linear-gradient(180deg, var(--bg-1) 0%, var(--bg-2) 50%, var(--bg-3) 100%);
  background-attachment: fixed;
  color: var(--text);
  min-height: 100vh;
  padding: 16px;
  user-select: none;
  -webkit-tap-highlight-color: transparent;
  overflow-x: hidden;
}

#app { max-width: 600px; margin: 0 auto; }
.screen { display: flex; flex-direction: column; gap: 16px; }
.hidden { display: none !important; }

/* Home header */
.home-header { text-align: center; padding: 8px 0 4px; }
h1 {
  font-size: 2.4rem; font-weight: 900; letter-spacing: -0.03em;
  text-transform: uppercase;
  color: var(--accent);
  text-shadow: 0 0 24px rgba(220, 255, 26, 0.25);
}
/* Keep the π glyph recognizable as math notation (italic serif, not uppercased) */
.pi-glyph {
  text-transform: none;
  font-family: 'Cambria', 'Georgia', 'Times New Roman', serif;
  font-style: italic;
  font-weight: 700;
  margin-right: 0.06em;
}
.subtitle { color: var(--text-dim); font-size: 0.95rem; margin-top: 4px; }

/* Stats */
.stats-bar { display: flex; gap: 10px; }
.stat {
  flex: 1; background: var(--card-bg); border: 1px solid var(--card-border);
  border-radius: 14px; padding: 12px; text-align: center;
}
.stat-label {
  display: block; font-size: 0.7rem; color: var(--text-dim);
  text-transform: uppercase; letter-spacing: 0.08em; margin-bottom: 4px;
}
.stat-value { font-size: 1.4rem; font-weight: 700; color: var(--accent); font-variant-numeric: tabular-nums; }

/* Progress bar */
.progress-bar { height: 10px; background: rgba(255,255,255,0.08); border-radius: 5px; overflow: hidden; }
.progress-fill {
  height: 100%; width: 0%;
  background: linear-gradient(90deg, var(--accent), var(--accent-2));
  transition: width 0.4s ease;
}

/* Mode grid */
.mode-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 10px; }
.mode-btn {
  background: var(--card-bg); border: 1px solid var(--card-border);
  border-radius: 14px; padding: 16px 12px; color: var(--text);
  cursor: pointer; transition: all 0.15s; text-align: left;
  font-family: inherit;
}
.mode-btn:hover { background: rgba(255,255,255,0.08); transform: translateY(-2px); border-color: var(--accent); }
.mode-btn:active { transform: translateY(0); }
.mode-icon { font-size: 1.7rem; margin-bottom: 4px; }
.mode-name { font-size: 1.05rem; font-weight: 700; margin-bottom: 2px; }
.mode-desc { font-size: 0.78rem; color: var(--text-dim); }

/* Settings row */
.settings-row {
  display: flex; justify-content: space-between; align-items: center;
  color: var(--text-dim); font-size: 0.85rem; padding: 4px 4px;
}
.settings-row label { display: flex; align-items: center; gap: 6px; cursor: pointer; }
.settings-row input[type="checkbox"] { accent-color: var(--accent); width: 16px; height: 16px; }
.link-btn {
  background: none; border: none; color: var(--text-dim);
  cursor: pointer; text-decoration: underline; font-size: inherit; font-family: inherit;
}
.link-btn:hover { color: var(--accent); }

/* Game screen */
.game-header { display: flex; align-items: center; gap: 10px; }
.back-btn {
  background: var(--card-bg); border: 1px solid var(--card-border);
  color: var(--text); padding: 8px 12px; border-radius: 10px;
  cursor: pointer; font-family: inherit; font-size: 0.9rem;
}
.back-btn:hover { background: rgba(255,255,255,0.10); }
.mode-title { flex: 1; text-align: center; font-weight: 700; font-size: 1.05rem; }
.game-stat {
  background: var(--card-bg); border: 1px solid var(--card-border);
  padding: 7px 11px; border-radius: 10px; font-size: 0.82rem;
  font-variant-numeric: tabular-nums; white-space: nowrap;
}

.game-content {
  min-height: 220px; padding: 20px 16px;
  background: var(--card-bg); border: 1px solid var(--card-border);
  border-radius: 16px;
  display: flex; flex-direction: column; gap: 12px;
}

/* Digit display */
.digit-stream {
  font-family: 'SF Mono', 'Menlo', 'Courier New', monospace;
  font-size: 1.5rem; line-height: 1.8;
  letter-spacing: 0.05em; word-break: break-all;
  text-align: center; padding: 8px 0;
}
.digit {
  display: inline-block; padding: 1px 2px; transition: color 0.2s, background 0.2s;
}
.digit.mastered { color: var(--text-dim); }
.digit.dot { color: var(--text-dim); }
.digit.current {
  color: var(--accent); background: rgba(220,255,26,0.14);
  border-radius: 4px; padding: 2px 7px; margin: 0 1px;
  animation: pulse 1.2s infinite;
}
.digit.correct { color: var(--correct); }
.digit.wrong { color: var(--wrong); background: rgba(239,68,68,0.18); border-radius: 4px; padding: 1px 5px; }
.digit.hidden-slot {
  color: transparent; background: rgba(255,255,255,0.12);
  border-radius: 4px; padding: 2px 7px; min-width: 1.1em;
  display: inline-block; margin: 0 1px;
}
.digit.hidden-slot.next {
  background: rgba(220,255,26,0.22); animation: pulse 1.2s infinite;
}
.digit.revealed { color: var(--text); animation: reveal 0.3s; }

@keyframes pulse { 0%, 100% { opacity: 1; } 50% { opacity: 0.6; } }
@keyframes reveal { from { transform: scale(0.5); opacity: 0; } to { transform: scale(1); opacity: 1; } }

.position-label { text-align: center; color: var(--text-dim); font-size: 0.85rem; }
.instruction { text-align: center; color: var(--text); font-size: 0.92rem; }
.feedback { text-align: center; min-height: 1.4em; font-weight: 600; font-size: 0.9rem; }
.feedback.good { color: var(--correct); }
.feedback.bad { color: var(--wrong); }

/* Number pad */
.number-pad {
  display: grid; grid-template-columns: repeat(3, 1fr); gap: 8px;
  margin-top: 4px;
}
.number-pad button {
  min-height: 56px; background: var(--card-bg); border: 1px solid var(--card-border);
  color: var(--text); border-radius: 12px; font-size: 1.5rem; font-weight: 700;
  cursor: pointer; font-family: inherit; transition: all 0.08s;
  font-variant-numeric: tabular-nums;
}
.number-pad button:hover { background: rgba(255,255,255,0.10); }
.number-pad button:active { background: var(--accent); color: #000; transform: scale(0.96); }
.number-pad button.zero { grid-column: 1 / 4; }

/* Action buttons */
.action-btn {
  background: var(--accent);
  border: none; color: #000; padding: 12px 22px; border-radius: 12px;
  font-weight: 800; cursor: pointer; font-size: 0.95rem; font-family: inherit;
  text-transform: uppercase; letter-spacing: 0.04em;
  transition: transform 0.1s, box-shadow 0.1s;
  box-shadow: 0 0 0 rgba(220,255,26,0);
}
.action-btn:hover { box-shadow: 0 4px 18px rgba(220,255,26,0.35); }
.action-btn:hover { transform: scale(1.03); }
.action-btn:active { transform: scale(0.97); }
.action-btn.secondary {
  background: var(--card-bg); color: var(--text); border: 1px solid var(--card-border);
}

.btn-row { display: flex; gap: 10px; justify-content: center; flex-wrap: wrap; }

/* Jump-to-digit row (Learn mode) */
.jump-row {
  display: flex; align-items: center; gap: 8px; flex-wrap: wrap;
  padding: 8px 10px; background: rgba(255,255,255,0.03);
  border: 1px solid var(--card-border); border-radius: 10px;
  font-size: 0.85rem; color: var(--text-dim);
}
.jump-row label { color: var(--text-dim); }
.jump-row input[type="number"] {
  width: 70px; background: #000; border: 1px solid var(--card-border);
  color: var(--text); border-radius: 8px; padding: 6px 8px;
  font-family: inherit; font-size: 0.95rem; text-align: center;
  -moz-appearance: textfield;
}
.jump-row input[type="number"]::-webkit-outer-spin-button,
.jump-row input[type="number"]::-webkit-inner-spin-button { -webkit-appearance: none; margin: 0; }
.jump-btn {
  background: var(--accent); color: #000; border: none;
  padding: 6px 12px; border-radius: 8px; font-weight: 700;
  font-family: inherit; font-size: 0.85rem; cursor: pointer;
  text-transform: uppercase; letter-spacing: 0.04em;
}
.jump-btn.secondary {
  background: transparent; color: var(--text-dim);
  border: 1px solid var(--card-border);
}
.jump-btn:hover { filter: brightness(1.1); }

/* Name input (Test mode) */
.name-row {
  display: flex; align-items: center; gap: 10px; justify-content: center;
  padding: 8px; flex-wrap: wrap;
}
.name-row label { color: var(--text-dim); font-size: 0.9rem; }
.name-row input[type="text"] {
  background: #000; border: 1px solid var(--card-border);
  color: var(--text); border-radius: 8px; padding: 8px 12px;
  font-family: inherit; font-size: 1rem; min-width: 160px;
}
.name-row input[type="text"]:focus { outline: none; border-color: var(--accent); }

/* Leaderboard */
.leaderboard-section {
  margin-top: 18px; padding-top: 14px;
  border-top: 1px solid var(--card-border);
}
.leaderboard-section h3 {
  font-size: 0.9rem; color: var(--text-dim);
  text-transform: uppercase; letter-spacing: 0.08em;
  margin-bottom: 8px; font-weight: 700;
}
.leaderboard {
  width: 100%; border-collapse: collapse; font-size: 0.88rem;
  font-variant-numeric: tabular-nums;
}
.leaderboard th {
  text-align: left; padding: 6px 8px; color: var(--text-dim);
  font-weight: 600; font-size: 0.75rem; text-transform: uppercase;
  letter-spacing: 0.05em; border-bottom: 1px solid var(--card-border);
}
.leaderboard td { padding: 6px 8px; border-bottom: 1px solid rgba(255,255,255,0.04); }
.leaderboard td:nth-child(1) { color: var(--text-dim); width: 1.5em; }
.leaderboard td:nth-child(3) { color: var(--accent); }
.leaderboard td:nth-child(4) { color: var(--text-dim); }
.leaderboard tr.highlight { background: rgba(220, 255, 26, 0.10); }
.leaderboard tr.highlight td { border-bottom-color: rgba(220, 255, 26, 0.2); }
.leaderboard-empty {
  color: var(--text-dim); font-style: italic; font-size: 0.9rem;
  text-align: center; padding: 12px;
}

.result-card { text-align: center; padding: 12px; }
.result-emoji { font-size: 3rem; margin-bottom: 6px; }
.result-card h2 { font-size: 1.4rem; margin-bottom: 4px; }
.result-card .sub { color: var(--text-dim); margin-top: 6px; font-size: 0.9rem; }

/* Confetti canvas */
#confetti-canvas {
  position: fixed; top: 0; left: 0; width: 100vw; height: 100vh;
  pointer-events: none; z-index: 100;
}

@media (max-width: 768px) {
  body { padding: 10px; }
  .screen { gap: 10px; }
  .game-content {
    padding: 14px 12px;
    max-height: calc(100vh - 360px);
    max-height: calc(100dvh - 360px);
    overflow-y: auto;
    min-height: 160px;
  }
  .digit-stream { font-size: 1.2rem; line-height: 1.7; padding: 4px 0; }
  .digit.current, .digit.hidden-slot, .digit.wrong { padding: 1px 5px; }
  .number-pad { gap: 6px; }
  .number-pad button { min-height: 46px; font-size: 1.2rem; }
  .leaderboard { font-size: 0.82rem; }
  .leaderboard th, .leaderboard td { padding: 5px 6px; }
}
@media (max-width: 480px) {
  h1 { font-size: 1.7rem; }
  .subtitle { font-size: 0.85rem; }
  .mode-grid { grid-template-columns: 1fr 1fr; gap: 8px; }
  .mode-btn { padding: 12px 10px; }
  .mode-icon { font-size: 1.5rem; }
  .mode-name { font-size: 0.98rem; }
  .mode-desc { font-size: 0.72rem; }
  .stat-value { font-size: 1.2rem; }
  .game-content {
    max-height: calc(100vh - 320px);
    max-height: calc(100dvh - 320px);
  }
  .digit-stream { font-size: 1.1rem; line-height: 1.65; letter-spacing: 0.03em; }
  .number-pad button { min-height: 42px; font-size: 1.1rem; }
  .action-btn { padding: 10px 18px; font-size: 0.9rem; }
}