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

:root {
  --bg:      #0f0f0f;
  --surface: #1a1a1a;
  --border:  rgba(255, 255, 255, 0.08);
  --text:    #ffffff;
  --muted:   rgba(255, 255, 255, 0.45);
  --accent:  #ff6b35;
}

html, body {
  height: 100%;
  background: var(--bg);
  color: var(--text);
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', system-ui, sans-serif;
  -webkit-tap-highlight-color: transparent;
  touch-action: manipulation;
  user-select: none;
  overflow: hidden;
}

.back-link {
  position: fixed;
  top: 1.2rem;
  left: 1.5rem;
  font-size: 0.65rem;
  font-weight: 600;
  letter-spacing: 0.2em;
  text-transform: uppercase;
  color: var(--muted);
  text-decoration: none;
  transition: color 0.2s;
  z-index: 10;
}
.back-link:hover { color: var(--text); }

/* ── Layout ────────────────────────────────────────── */

.app {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  height: 100svh;
  gap: clamp(1.25rem, 4vh, 2.25rem);
  padding: 4rem 1.5rem 2rem;
}

/* ── Beat dots ─────────────────────────────────────── */

.beat-row {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 0.6rem;
  max-width: 320px;
}

.beat-dot {
  width: 18px;
  height: 18px;
  border-radius: 50%;
  background: transparent;
  border: 2px solid rgba(255, 255, 255, 0.14);
  transition: background 0.04s, box-shadow 0.04s;
}

.beat-dot.accent {
  border-color: rgba(255, 107, 53, 0.5);
}

.beat-dot.active {
  background: var(--accent);
  border-color: var(--accent);
  box-shadow: 0 0 14px var(--accent);
}

/* ── BPM display ───────────────────────────────────── */

.bpm-area {
  text-align: center;
  line-height: 1;
}

.bpm-number {
  font-size: clamp(88px, 24vw, 144px);
  font-weight: 700;
  letter-spacing: -0.03em;
  color: var(--text);
  cursor: ns-resize;
  line-height: 1;
  touch-action: none;
}

.bpm-label {
  margin-top: 0.4rem;
  font-size: 0.7rem;
  font-weight: 700;
  letter-spacing: 0.3em;
  text-transform: uppercase;
  color: var(--muted);
}

/* ── +/− + slider row ──────────────────────────────── */

.adj-row {
  display: flex;
  align-items: center;
  gap: 1rem;
  width: 100%;
  max-width: 300px;
}

.btn-adj {
  flex-shrink: 0;
  width: 44px;
  height: 44px;
  border-radius: 50%;
  border: 2px solid var(--border);
  background: var(--surface);
  color: var(--text);
  font-size: 1.4rem;
  line-height: 1;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: border-color 0.12s, background 0.12s;
}
.btn-adj:active {
  background: var(--accent);
  border-color: var(--accent);
}

#bpm-slider {
  flex: 1;
  -webkit-appearance: none;
  appearance: none;
  height: 4px;
  background: var(--border);
  border-radius: 2px;
  outline: none;
  cursor: pointer;
}
#bpm-slider::-webkit-slider-thumb {
  -webkit-appearance: none;
  width: 22px;
  height: 22px;
  border-radius: 50%;
  background: var(--accent);
  box-shadow: 0 0 8px rgba(255, 107, 53, 0.5);
}
#bpm-slider::-moz-range-thumb {
  width: 22px;
  height: 22px;
  border-radius: 50%;
  background: var(--accent);
  border: none;
  box-shadow: 0 0 8px rgba(255, 107, 53, 0.5);
}

/* ── Time signature row ────────────────────────────── */

.time-sig-row {
  display: flex;
  align-items: center;
  gap: 0.75rem;
}

.ts-display {
  font-size: 1rem;
  font-weight: 600;
  color: var(--muted);
  min-width: 3.5rem;
  text-align: center;
}
.ts-denom {
  opacity: 0.5;
}

.btn-sm {
  width: 30px;
  height: 30px;
  border-radius: 50%;
  border: 1px solid var(--border);
  background: transparent;
  color: var(--muted);
  font-size: 1.1rem;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: color 0.15s, border-color 0.15s;
}
.btn-sm:hover {
  color: var(--text);
  border-color: rgba(255, 255, 255, 0.25);
}
.btn-sm:active {
  color: var(--accent);
}

/* ── Action row ────────────────────────────────────── */

.action-row {
  display: flex;
  align-items: center;
  gap: 1.75rem;
}

.btn-tap {
  padding: 0 1.5rem;
  height: 52px;
  border-radius: 26px;
  border: 2px solid var(--border);
  background: var(--surface);
  color: var(--text);
  font-size: 0.7rem;
  font-weight: 700;
  letter-spacing: 0.25em;
  text-transform: uppercase;
  cursor: pointer;
  transition: border-color 0.1s;
}
.btn-tap:active {
  border-color: var(--accent);
}

.btn-play {
  width: 76px;
  height: 76px;
  border-radius: 50%;
  border: none;
  background: var(--accent);
  color: #fff;
  font-size: 1.6rem;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  box-shadow: 0 4px 24px rgba(255, 107, 53, 0.45);
  transition: transform 0.1s, box-shadow 0.1s;
}
.btn-play:active {
  transform: scale(0.93);
}
.btn-play.playing {
  background: var(--surface);
  border: 2px solid var(--accent);
  box-shadow: 0 0 22px rgba(255, 107, 53, 0.3);
}