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

:root {
  --primary: #2563eb;
  --primary-dark: #1d4ed8;
  --success: #16a34a;
  --warning: #d97706;
  --danger: #dc2626;
  --bg: #f1f5f9;
  --card: #ffffff;
  --text: #1e293b;
  --text-light: #64748b;
  --border: #e2e8f0;
  --sidebar-width: 220px;
  --navbar-height: 60px;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  background: var(--bg);
  color: var(--text);
  min-height: 100vh;
}

.page { display: none; }
.page.active { display: block; }
.section { display: none; }
.section.active { display: block; }

.login-container {
  display: flex;
  align-items: center;
  justify-content: center;
  min-height: 100vh;
  padding: 1rem;
}

.login-card {
  background: var(--card);
  border-radius: 12px;
  padding: 2.5rem;
  width: 100%;
  max-width: 400px;
  box-shadow: 0 4px 24px rgba(0,0,0,0.08);
}

.login-card h1 {
  text-align: center;
  color: var(--primary);
  margin-bottom: 0.25rem;
}

.subtitle {
  text-align: center;
  color: var(--text-light);
  margin-bottom: 2rem;
}

.form-group {
  margin-bottom: 1.25rem;
}

.form-group label {
  display: block;
  font-size: 0.875rem;
  font-weight: 500;
  margin-bottom: 0.4rem;
  color: var(--text);
}

.form-group input, .form-group select {
  width: 100%;
  padding: 0.7rem 1rem;
  border: 1px solid var(--border);
  border-radius: 8px;
  font-size: 0.9rem;
  transition: border-color 0.2s;
}

.form-group input:focus, .form-group select:focus {
  outline: none;
  border-color: var(--primary);
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 0.6rem 1.2rem;
  border: none;
  border-radius: 8px;
  font-size: 0.875rem;
  font-weight: 500;
  cursor: pointer;
  transition: all 0.2s;
  text-decoration: none;
}

.btn-primary { background: var(--primary); color: white; }
.btn-primary:hover { background: var(--primary-dark); }
.btn-success { background: var(--success); color: white; }
.btn-danger { background: var(--danger); color: white; }
.btn-outline { background: transparent; border: 1px solid var(--border); color: var(--text); }
.btn-outline:hover { background: var(--bg); }
.btn-sm { padding: 0.4rem 0.8rem; font-size: 0.8rem; }
.btn-block { width: 100%; }

.error-text {
  color: var(--danger);
  font-size: 0.85rem;
  margin-top: 0.75rem;
  text-align: center;
}

.navbar {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  height: var(--navbar-height);
  background: var(--card);
  border-bottom: 1px solid var(--border);
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 1.5rem;
  z-index: 100;
}

.nav-brand {
  font-size: 1.2rem;
  font-weight: 700;
  color: var(--primary);
}

.nav-user {
  display: flex;
  align-items: center;
  gap: 1rem;
}

.sidebar {
  position: fixed;
  top: var(--navbar-height);
  left: 0;
  width: var(--sidebar-width);
  height: calc(100vh - var(--navbar-height));
  background: var(--card);
  border-right: 1px solid var(--border);
  padding: 1rem 0;
  overflow-y: auto;
}

.nav-link {
  display: block;
  padding: 0.75rem 1.5rem;
  color: var(--text-light);
  text-decoration: none;
  font-size: 0.9rem;
  transition: all 0.2s;
}

.nav-link:hover { background: var(--bg); color: var(--text); }
.nav-link.active { color: var(--primary); background: #eff6ff; border-right: 3px solid var(--primary); }

.content {
  margin-left: var(--sidebar-width);
  margin-top: var(--navbar-height);
  padding: 2rem;
}

.section-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 1.5rem;
}

.stats-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 1rem;
  margin-bottom: 1.5rem;
}

.stat-card {
  background: var(--card);
  border-radius: 10px;
  padding: 1.25rem;
  box-shadow: 0 1px 4px rgba(0,0,0,0.04);
}

.stat-card .stat-label {
  font-size: 0.8rem;
  color: var(--text-light);
  text-transform: uppercase;
  letter-spacing: 0.5px;
}

.stat-card .stat-value {
  font-size: 1.75rem;
  font-weight: 700;
  margin-top: 0.25rem;
}

.stat-card .stat-value.primary { color: var(--primary); }
.stat-card .stat-value.success { color: var(--success); }
.stat-card .stat-value.warning { color: var(--warning); }

.card {
  background: var(--card);
  border-radius: 10px;
  padding: 1.5rem;
  box-shadow: 0 1px 4px rgba(0,0,0,0.04);
}

.mt-2 { margin-top: 1.5rem; }

.table {
  width: 100%;
  border-collapse: collapse;
}

.table th, .table td {
  padding: 0.75rem 1rem;
  text-align: left;
  border-bottom: 1px solid var(--border);
  font-size: 0.875rem;
}

.table th {
  font-weight: 600;
  color: var(--text-light);
  font-size: 0.8rem;
  text-transform: uppercase;
}

.table tbody tr:hover { background: #f8fafc; }

.badge {
  display: inline-block;
  padding: 0.2rem 0.6rem;
  border-radius: 20px;
  font-size: 0.75rem;
  font-weight: 500;
}

.badge-success { background: #dcfce7; color: #166534; }
.badge-warning { background: #fef3c7; color: #92400e; }
.badge-danger { background: #fef2f2; color: #991b1b; }

.filters {
  display: flex;
  gap: 0.75rem;
  align-items: center;
}

.filters select {
  padding: 0.5rem 1rem;
  border: 1px solid var(--border);
  border-radius: 8px;
  font-size: 0.875rem;
}

.pagination {
  display: flex;
  justify-content: center;
  gap: 0.5rem;
  margin-top: 1rem;
}

.modal-overlay {
  display: none;
  position: fixed;
  inset: 0;
  background: rgba(0,0,0,0.5);
  z-index: 200;
  align-items: center;
  justify-content: center;
}

.modal-overlay.active { display: flex; }

.modal {
  background: var(--card);
  border-radius: 12px;
  width: 100%;
  max-width: 500px;
  max-height: 90vh;
  overflow-y: auto;
}

.modal-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 1.25rem 1.5rem;
  border-bottom: 1px solid var(--border);
}

.modal-body { padding: 1.5rem; }

.btn-close {
  background: none;
  border: none;
  font-size: 1.5rem;
  cursor: pointer;
  color: var(--text-light);
}

.device-card {
  background: var(--bg);
  border-radius: 8px;
  padding: 1rem;
  margin-bottom: 0.75rem;
}

.device-card .device-name { font-weight: 600; }
.device-card .device-info { font-size: 0.85rem; color: var(--text-light); margin-top: 0.25rem; }
.device-card .device-power { font-size: 1.2rem; font-weight: 700; color: var(--primary); margin-top: 0.5rem; }

.hidden { display: none !important; }

@media (max-width: 768px) {
  .sidebar { display: none; }
  .content { margin-left: 0; }
  .stats-grid { grid-template-columns: 1fr 1fr; }
  .filters { flex-wrap: wrap; }
}