:root {
  --bg: #ffffff;
  --text: #111111;
  --muted: #666666;
  --border: #dddddd;
  --accent: #000000;
  --accent-text: #ffffff;
  --danger: #cc0000;
  --running: #006600;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.5;
}

.app {
  max-width: 560px;
  margin: 0 auto;
  padding: 24px 16px 48px;
}

header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 32px;
}

h1 {
  font-size: 1.25rem;
  font-weight: 600;
  margin: 0;
}

h2 {
  font-size: 1rem;
  font-weight: 600;
  margin: 0 0 12px;
}

button {
  font: inherit;
  cursor: pointer;
  border: 1px solid var(--border);
  background: var(--bg);
  color: var(--text);
  padding: 8px 14px;
  border-radius: 0;
}

button.ghost {
  border-color: transparent;
  text-decoration: underline;
  padding: 4px 6px;
}

button.primary {
  background: var(--accent);
  color: var(--accent-text);
  border-color: var(--accent);
}

button.danger {
  color: var(--danger);
  border-color: var(--danger);
}

.action {
  text-align: center;
  margin-bottom: 32px;
}

.status {
  font-size: 0.875rem;
  color: var(--muted);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  margin-bottom: 8px;
}

.status.running {
  color: var(--running);
}

.session-time {
  font-size: 3rem;
  font-weight: 300;
  font-variant-numeric: tabular-nums;
  margin-bottom: 20px;
}

.action-btn {
  width: 100%;
  padding: 20px 24px;
  font-size: 1.25rem;
  font-weight: 600;
  background: var(--accent);
  color: var(--accent-text);
  border: none;
}

.action-btn.stop {
  background: var(--danger);
}

.settings {
  border: 1px solid var(--border);
  padding: 16px;
  margin-bottom: 24px;
}

.settings.hidden {
  display: none;
}

.settings label {
  display: block;
  margin-bottom: 12px;
  font-size: 0.875rem;
}

.settings input {
  display: block;
  width: 100%;
  margin-top: 4px;
  padding: 8px;
  font: inherit;
  border: 1px solid var(--border);
  border-radius: 0;
}

.settings button {
  margin-top: 8px;
  margin-right: 8px;
}

.stats {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 12px;
  margin-bottom: 32px;
}

.stat {
  border: 1px solid var(--border);
  padding: 14px;
}

.stat-label {
  display: block;
  font-size: 0.75rem;
  color: var(--muted);
  text-transform: uppercase;
  letter-spacing: 0.03em;
  margin-bottom: 4px;
}

.stat-value {
  display: block;
  font-size: 1.5rem;
  font-weight: 600;
  font-variant-numeric: tabular-nums;
}

.sessions ul {
  list-style: none;
  margin: 0;
  padding: 0;
  border-top: 1px solid var(--border);
}

.sessions li {
  display: flex;
  justify-content: space-between;
  padding: 10px 0;
  border-bottom: 1px solid var(--border);
  font-size: 0.875rem;
}

.sessions .empty {
  color: var(--muted);
}

@media (max-width: 420px) {
  .stats {
    grid-template-columns: 1fr;
  }

  .session-time {
    font-size: 2.25rem;
  }
}