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

:root {
  --bg: #f9fafb;
  --surface: #ffffff;
  --border: #e5e7eb;
  --text: #111827;
  --text-secondary: #6b7280;
  --accent: #3b82f6;
  --accent-light: #eff6ff;
  --radius: 8px;
}

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

/* --- Header --- */

header {
  background: var(--surface);
  border-bottom: 1px solid var(--border);
  padding: 16px 24px;
}

header h1 {
  font-size: 20px;
  font-weight: 700;
  margin-bottom: 12px;
}

header h1 span {
  color: var(--text-secondary);
  font-weight: 400;
}

/* --- Device tabs --- */

.tabs {
  display: flex;
  gap: 6px;
  flex-wrap: wrap;
}

.tab {
  padding: 6px 16px;
  border: 1px solid var(--border);
  border-radius: 20px;
  background: var(--surface);
  color: var(--text-secondary);
  font-size: 14px;
  font-weight: 500;
  cursor: pointer;
  transition: all 0.15s;
}

.tab:hover {
  border-color: var(--accent);
  color: var(--accent);
}

.tab.active {
  background: var(--accent);
  border-color: var(--accent);
  color: #fff;
}

/* --- Controls bar --- */

.controls {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 12px 24px;
  flex-wrap: wrap;
}

.model-badge {
  display: inline-block;
  padding: 2px 10px;
  border-radius: 12px;
  background: #f3f4f6;
  color: var(--text-secondary);
  font-size: 12px;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.range-buttons {
  display: flex;
  gap: 4px;
}

.range-btn {
  padding: 4px 12px;
  border: 1px solid var(--border);
  border-radius: 6px;
  background: var(--surface);
  color: var(--text-secondary);
  font-size: 13px;
  cursor: pointer;
  transition: all 0.15s;
}

.range-btn:hover {
  border-color: var(--accent);
  color: var(--accent);
}

.range-btn.active {
  background: var(--accent-light);
  border-color: var(--accent);
  color: var(--accent);
}

.custom-dates {
  display: none;
  gap: 8px;
  align-items: center;
}

.custom-dates input {
  padding: 4px 8px;
  border: 1px solid var(--border);
  border-radius: 6px;
  font-size: 13px;
  color: var(--text);
}

.status {
  margin-left: auto;
  font-size: 13px;
  color: var(--text-secondary);
}

/* --- Latest readings --- */

.latest-readings {
  display: flex;
  gap: 12px;
  padding: 0 24px 12px;
  flex-wrap: wrap;
}

.reading-card {
  display: flex;
  flex-direction: column;
  align-items: center;
  padding: 8px 16px;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  min-width: 90px;
}

.reading-value {
  font-size: 22px;
  font-weight: 700;
  line-height: 1.2;
}

.reading-label {
  font-size: 11px;
  color: var(--text-secondary);
  font-weight: 500;
}

.reading-unit {
  font-size: 11px;
  color: var(--text-secondary);
}

/* --- Chart grid --- */

.chart-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 16px;
  padding: 0 24px 24px;
}

.chart-wrapper {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 16px;
  height: 280px;
}

.chart-wrapper canvas {
  width: 100% !important;
  height: 100% !important;
}

.empty-msg {
  grid-column: 1 / -1;
  text-align: center;
  padding: 48px;
  color: var(--text-secondary);
  font-size: 15px;
}

.loading-text {
  color: var(--text-secondary);
  font-size: 14px;
}

/* --- Responsive --- */

@media (max-width: 768px) {
  .chart-grid {
    grid-template-columns: 1fr;
    padding: 0 12px 12px;
  }

  header {
    padding: 12px;
  }

  .controls {
    padding: 8px 12px;
  }

  .latest-readings {
    padding: 0 12px 8px;
  }

  .status {
    margin-left: 0;
    width: 100%;
  }
}