:root {
  /* Light Slate Grey & Steel Blue System */
  --bg-primary: #f8fafc;
  --bg-surface: #f1f5f9;
  --bg-card: rgba(255, 255, 255, 0.85);
  --bg-card-hover: rgba(255, 255, 255, 0.95);

  --border-color: #e2e8f0;
  --border-subtle: #f1f5f9;
  --border-hover: #cbd5e1;

  --text-main: #0f172a;
  --text-secondary: #475569;
  --text-muted: #64748b;

  /* Steel Blue & Functional Accents */
  --accent-blue: #2563eb;
  --accent-blue-hover: #1d4ed8;
  --accent-emerald: #059669;
  --accent-amber: #d97706;
  --accent-rose: #dc2626;

  --font-family: 'Inter', -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
}

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

body {
  background: var(--bg-primary);
  color: var(--text-main);
  font-family: var(--font-family);
  min-height: 100vh;
  overflow-x: hidden;
  background-image: 
    radial-gradient(at 0% 0%, rgba(37, 99, 235, 0.04) 0px, transparent 50%),
    radial-gradient(at 100% 100%, rgba(100, 116, 139, 0.05) 0px, transparent 50%);
  background-attachment: fixed;
}

.app-container {
  display: grid;
  grid-template-columns: 260px 1fr;
  min-height: 100vh;
}

/* Sidebar Navigation */
.sidebar {
  background: rgba(248, 250, 252, 0.85);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border-right: 1px solid var(--border-color);
  padding: 24px 20px;
  display: flex;
  flex-direction: column;
  gap: 32px;
}

.brand {
  display: flex;
  align-items: center;
  gap: 12px;
  font-size: 1.15rem;
  font-weight: 700;
  color: var(--text-main);
  letter-spacing: -0.3px;
}

.brand-badge {
  background: rgba(37, 99, 235, 0.1);
  color: var(--accent-blue);
  padding: 3px 8px;
  border-radius: 4px;
  font-size: 0.7rem;
  font-weight: 700;
  letter-spacing: 0.5px;
  border: 1px solid rgba(37, 99, 235, 0.2);
}

.nav-list {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 4px;
}

.nav-item a {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 10px 14px;
  border-radius: 8px;
  color: var(--text-secondary);
  text-decoration: none;
  font-size: 0.88rem;
  font-weight: 500;
  transition: all 0.15s ease;
}

.nav-item.active a, .nav-item a:hover {
  background: rgba(37, 99, 235, 0.08);
  color: var(--accent-blue-hover);
  border: 1px solid rgba(37, 99, 235, 0.18);
}

.nav-item.active a {
  font-weight: 600;
}

/* Main Content Views */
.main-content {
  padding: 32px;
  display: flex;
  flex-direction: column;
  gap: 24px;
  overflow-y: auto;
}

.view-container {
  display: none;
}

.view-container.active {
  display: block;
}

/* Header & Top Bar */
.top-bar {
  display: flex;
  justify-content: space-between;
  align-items: center;
  background: var(--bg-card);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border: 1px solid var(--border-color);
  padding: 16px 24px;
  border-radius: 12px;
  box-shadow: 0 4px 16px rgba(15, 23, 42, 0.04);
}

.tenant-selector {
  display: flex;
  align-items: center;
  gap: 16px;
}

.tenant-selector label {
  font-size: 0.8rem;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 0.5px;
  font-weight: 600;
}

.tenant-inputs {
  display: flex;
  gap: 12px;
}

.tenant-input {
  background: #ffffff;
  border: 1px solid var(--border-color);
  color: var(--text-main);
  padding: 8px 12px;
  border-radius: 6px;
  font-size: 0.85rem;
  width: 110px;
  outline: none;
  transition: border-color 0.15s ease, box-shadow 0.15s ease;
}

.tenant-input:focus {
  border-color: var(--accent-blue);
  box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.12);
}

/* Sections & Cards */
.section-title {
  font-size: 1.1rem;
  font-weight: 600;
  margin-bottom: 16px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  color: var(--text-main);
  letter-spacing: -0.2px;
}

.content-card {
  background: var(--bg-card);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border: 1px solid var(--border-color);
  border-radius: 12px;
  padding: 24px;
  margin-bottom: 24px;
  box-shadow: 0 4px 16px rgba(15, 23, 42, 0.04);
}

/* Data Tables */
.data-table-container {
  width: 100%;
  overflow-x: auto;
  border-radius: 8px;
  border: 1px solid var(--border-color);
  background: #ffffff;
}

.data-table {
  width: 100%;
  border-collapse: collapse;
  text-align: left;
  font-size: 0.88rem;
}

.data-table th {
  background: #f8fafc;
  color: var(--text-secondary);
  font-weight: 600;
  text-transform: uppercase;
  font-size: 0.72rem;
  letter-spacing: 0.5px;
  padding: 12px 16px;
  border-bottom: 1px solid var(--border-color);
}

.data-table td {
  padding: 12px 16px;
  border-bottom: 1px solid var(--border-subtle);
  color: var(--text-main);
}

.data-table tr:hover {
  background: #f8fafc;
}

.data-table tr.clickable-row {
  cursor: pointer;
}

.data-table tr.clickable-row:hover {
  background: rgba(37, 99, 235, 0.05);
}

/* Device Fleet Grid */
.device-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
  gap: 16px;
}

.device-card {
  background: var(--bg-card);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border: 1px solid var(--border-color);
  border-radius: 12px;
  padding: 20px;
  display: flex;
  flex-direction: column;
  gap: 16px;
  transition: all 0.2s ease;
  box-shadow: 0 4px 12px rgba(15, 23, 42, 0.03);
}

.device-card:hover {
  background: var(--bg-card-hover);
  border-color: var(--border-hover);
  transform: translateY(-2px);
  box-shadow: 0 8px 24px rgba(15, 23, 42, 0.08);
}

.device-header {
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
}

.device-id {
  font-weight: 700;
  font-size: 1rem;
  color: var(--text-main);
}

.device-oem {
  font-size: 0.78rem;
  color: var(--text-muted);
}

.status-badge {
  padding: 3px 9px;
  border-radius: 12px;
  font-size: 0.72rem;
  font-weight: 600;
  display: inline-flex;
  align-items: center;
  gap: 5px;
}

.status-badge.online {
  background: rgba(5, 150, 105, 0.1);
  color: var(--accent-emerald);
  border: 1px solid rgba(5, 150, 105, 0.25);
}

.status-badge.offline {
  background: rgba(220, 38, 38, 0.1);
  color: var(--accent-rose);
  border: 1px solid rgba(220, 38, 38, 0.25);
}

.device-details {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 12px;
  font-size: 0.82rem;
}

.detail-item {
  display: flex;
  flex-direction: column;
  gap: 2px;
}

.detail-label {
  color: var(--text-muted);
  font-size: 0.72rem;
  text-transform: uppercase;
  letter-spacing: 0.4px;
}

.detail-value {
  color: var(--text-main);
  font-weight: 600;
}

/* Action Buttons */
.card-actions {
  display: flex;
  gap: 8px;
  margin-top: 8px;
}

.btn {
  background: #ffffff;
  border: 1px solid var(--border-color);
  color: var(--text-main);
  padding: 8px 14px;
  border-radius: 6px;
  font-size: 0.8rem;
  font-weight: 600;
  cursor: pointer;
  transition: all 0.15s ease;
  flex: 1;
  text-align: center;
  box-shadow: 0 1px 2px rgba(15, 23, 42, 0.04);
}

.btn:hover {
  background: #f8fafc;
  border-color: var(--border-hover);
}

.btn-primary {
  background: var(--accent-blue);
  color: #ffffff;
  border: 1px solid #1d4ed8;
  box-shadow: 0 1px 3px rgba(37, 99, 235, 0.2);
}

.btn-primary:hover {
  background: var(--accent-blue-hover);
}

.btn-danger {
  background: rgba(220, 38, 38, 0.08);
  color: #b91c1c;
  border: 1px solid rgba(220, 38, 38, 0.2);
}

.btn-danger:hover {
  background: rgba(220, 38, 38, 0.15);
}

/* Modal System */
.modal-overlay {
  position: fixed;
  top: 0;
  left: 0;
  width: 100vw;
  height: 100vh;
  background: rgba(15, 23, 42, 0.35);
  backdrop-filter: blur(8px);
  -webkit-backdrop-filter: blur(8px);
  display: none;
  align-items: center;
  justify-content: center;
  z-index: 999;
}

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

.modal {
  background: rgba(255, 255, 255, 0.95);
  backdrop-filter: blur(20px);
  -webkit-backdrop-filter: blur(20px);
  border: 1px solid var(--border-color);
  border-radius: 14px;
  width: 100%;
  max-width: 480px;
  padding: 28px;
  display: flex;
  flex-direction: column;
  gap: 20px;
  box-shadow: 0 20px 40px rgba(15, 23, 42, 0.12);
}

.modal-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.modal-title {
  font-size: 1.05rem;
  font-weight: 700;
  color: var(--text-main);
}

.form-group {
  display: flex;
  flex-direction: column;
  gap: 6px;
}

.form-group label {
  font-size: 0.8rem;
  color: var(--text-secondary);
  font-weight: 500;
}

.form-control {
  background: #ffffff;
  border: 1px solid var(--border-color);
  color: var(--text-main);
  padding: 10px 14px;
  border-radius: 6px;
  font-size: 0.88rem;
  outline: none;
  transition: border-color 0.15s ease, box-shadow 0.15s ease;
}

.form-control:focus {
  border-color: var(--accent-blue);
  box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.12);
}

select.form-control option {
  background: #ffffff;
  color: #0f172a;
}

/* Custom Scrollbars */
::-webkit-scrollbar {
  width: 6px;
  height: 6px;
}

::-webkit-scrollbar-track {
  background: rgba(241, 245, 249, 0.5);
}

::-webkit-scrollbar-thumb {
  background: rgba(148, 163, 184, 0.4);
  border-radius: 3px;
}

::-webkit-scrollbar-thumb:hover {
  background: rgba(100, 116, 139, 0.6);
}