:root {
  --bg: #0d1117;
  --panel: #161b22;
  --border: #2a3140;
  --text: #e6edf3;
  --muted: #8b949e;
  --accent: #4d7cff;
  --temp: #ff9d4d;
  --humidity: #4dc9ff;
  --gas: #53e88b;
  --heart: #ff4d5e;
}

* {
  box-sizing: border-box;
  margin: 0;
}

body {
  min-height: 100vh;
  background: var(--bg);
  color: var(--text);
  font-family: system-ui, -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  display: flex;
  flex-direction: column;
  align-items: center;
  padding: 1rem;
}

main {
  width: 100%;
  max-width: 640px;
}

.header h1 {
  font-size: clamp(1.5rem, 5vw, 2rem);
  font-weight: 700;
  text-align: center;
  margin: 0.5rem 0 1.5rem;
}

/* ---------- Connect bar ---------- */
.connect-bar {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  flex-wrap: wrap;
}

.btn {
  background: var(--accent);
  color: #fff;
  border: none;
  border-radius: 8px;
  padding: 0.6rem 1.2rem;
  font-size: 1rem;
  font-weight: 600;
  cursor: pointer;
}

.btn.disconnect {
  background: #3a2b2e;
  color: var(--heart);
}

.btn:disabled {
  opacity: 0.5;
  cursor: not-allowed;
}

.status {
  color: var(--muted);
  font-size: 0.9rem;
}

.status.measuring {
  color: var(--heart);
}

.hint {
  color: var(--muted);
  font-size: 0.85rem;
  margin: 0.75rem 0 1.5rem;
}

/* ---------- Cards ---------- */
.cards {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 0.75rem;
}

.card {
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 1rem 1.1rem;
  display: flex;
  flex-direction: column;
  gap: 0.35rem;
  text-align: center;
}

.label {
  font-size: 0.72rem;
  text-transform: uppercase;
  letter-spacing: 1px;
  color: var(--muted);
}

.value {
  font-size: clamp(1.9rem, 8vw, 2.5rem);
  font-weight: 700;
  line-height: 1.1;
  font-variant-numeric: tabular-nums;
  word-break: break-word;
}

.temp { color: var(--temp); }
.humidity { color: var(--humidity); }
.gas { color: var(--gas); }
.heart { color: var(--heart); }

.note {
  font-size: 0.72rem;
  color: var(--muted);
  min-height: 1em;
}

/* ---------- Graph ---------- */
.graph-card {
  margin-top: 0.75rem;
}

.graph-card .label {
  margin-bottom: 0.5rem;
  display: block;
  text-align: center;
}

#bpmChart {
  width: 100%;
  height: 220px;
  display: block;
}

/* ---------- Small screens ---------- */
@media (max-width: 380px) {
  .cards {
    grid-template-columns: 1fr;
  }

  .value {
    font-size: 2.2rem;
  }

  #bpmChart {
    height: 180px;
  }
}