:root {
  /* Premium Dark Flat Design System Tokens */
  --bg-primary: #0F0F11;
  --bg-card: #17171C;
  --bg-modal: #1E1E24;
  --border-color: #282830;
  
  --text-main: #F3F4F6;
  --text-secondary: #9CA3AF;
  --text-muted: #6B7280;
  
  --accent-green: #10B981;
  --accent-green-light: rgba(16, 185, 129, 0.15);
  --accent-blue: #3B82F6;
  --accent-blue-light: rgba(59, 130, 246, 0.1);
  --accent-blue-hover: #2563EB;
  
  --danger: #EF4444;
  --danger-light: rgba(239, 68, 68, 0.1);
  --danger-hover: #DC2626;

  --btn-flat-bg: #22222A;
  --btn-flat-hover: #2E2E38;

  --radius-lg: 16px;
  --radius-md: 12px;
  --radius-sm: 8px;
  
  --font-family: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
  --transition-speed: 0.2s;
}

/* Reset & Core Styles */
* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
  -webkit-tap-highlight-color: transparent;
}

body {
  font-family: var(--font-family);
  background-color: var(--bg-primary);
  color: var(--text-main);
  padding: 16px;
  font-size: 15px;
  line-height: 1.5;
  overflow-x: hidden;
  -webkit-font-smoothing: antialiased;
}

.app-container {
  max-width: 500px;
  margin: 0 auto;
  display: flex;
  flex-direction: column;
  gap: 16px;
}

/* Icons */
.icon {
  width: 20px;
  height: 20px;
}
.icon-sm {
  width: 16px;
  height: 16px;
}

/* Buttons */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  font-family: var(--font-family);
  font-size: 14px;
  font-weight: 600;
  padding: 12px 20px;
  border-radius: var(--radius-md);
  border: 1px solid transparent;
  cursor: pointer;
  transition: background-color var(--transition-speed), transform 0.1s ease;
}

.btn:active {
  transform: scale(0.97);
}

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

.btn-secondary {
  background-color: var(--btn-flat-bg);
  border-color: var(--border-color);
  color: var(--text-main);
}
.btn-secondary:hover {
  background-color: var(--btn-flat-hover);
}

.btn-flat {
  background-color: transparent;
  color: var(--text-secondary);
}
.btn-flat:hover {
  background-color: var(--btn-flat-bg);
  color: var(--text-main);
}

.btn-danger-flat {
  background-color: transparent;
  color: var(--danger);
}
.btn-danger-flat:hover {
  background-color: var(--danger-light);
}

.btn-sm {
  padding: 8px 14px;
  font-size: 13px;
  border-radius: var(--radius-sm);
}

/* User Header Card */
.user-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  background-color: var(--bg-card);
  border: 1px solid var(--border-color);
  padding: 16px;
  border-radius: var(--radius-lg);
}

.user-info {
  display: flex;
  align-items: center;
  gap: 12px;
}

.user-avatar {
  width: 48px;
  height: 48px;
  border-radius: 50%;
  background-color: var(--accent-blue-light);
  color: var(--accent-blue);
  font-size: 20px;
  font-weight: 700;
  display: flex;
  align-items: center;
  justify-content: center;
  border: 1px solid rgba(59, 130, 246, 0.2);
}

.user-meta {
  display: flex;
  flex-direction: column;
}

.user-name {
  font-size: 16px;
  font-weight: 600;
}

.user-handle {
  font-size: 13px;
  color: var(--text-secondary);
}

.status-badge {
  font-size: 12px;
  font-weight: 700;
  padding: 4px 10px;
  border-radius: 9999px;
  border: 1px solid transparent;
}

.status-badge.active {
  background-color: var(--accent-green-light);
  color: var(--accent-green);
  border-color: rgba(16, 185, 129, 0.2);
}

.status-badge.inactive {
  background-color: var(--danger-light);
  color: var(--danger);
  border-color: rgba(239, 68, 68, 0.2);
}

/* Balance Card */
.balance-card {
  display: flex;
  justify-content: space-between;
  align-items: center;
  background-color: var(--bg-card);
  border: 1px solid var(--border-color);
  padding: 20px;
  border-radius: var(--radius-lg);
}

.balance-info {
  display: flex;
  flex-direction: column;
  gap: 4px;
}

.balance-label {
  font-size: 13px;
  color: var(--text-secondary);
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.balance-amount {
  font-size: 28px;
  font-weight: 700;
  color: var(--accent-green);
}

/* Tabs Navigation */
.nav-tabs {
  display: flex;
  background-color: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  padding: 4px;
}

.tab-btn {
  flex: 1;
  background: transparent;
  border: none;
  font-family: var(--font-family);
  font-size: 14px;
  font-weight: 600;
  color: var(--text-secondary);
  padding: 10px;
  cursor: pointer;
  border-radius: var(--radius-sm);
  transition: color var(--transition-speed), background-color var(--transition-speed);
}

.tab-btn.active {
  background-color: var(--btn-flat-bg);
  color: var(--text-main);
}

/* Tabs Content */
.tab-pane {
  display: none;
  flex-direction: column;
  gap: 16px;
}

.tab-pane.active {
  display: flex;
}

.section-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-top: 8px;
}

.section-header h3 {
  font-size: 16px;
  font-weight: 600;
  color: var(--text-main);
}

/* Devices List */
.devices-list {
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.loading-state, .empty-state {
  text-align: center;
  padding: 40px 20px;
  background-color: var(--bg-card);
  border: 1px dashed var(--border-color);
  border-radius: var(--radius-lg);
  color: var(--text-secondary);
}

.empty-state h4 {
  color: var(--text-main);
  margin-bottom: 6px;
  font-weight: 600;
}

.empty-state p {
  font-size: 13px;
}

.device-card {
  display: flex;
  flex-direction: column;
  background-color: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  padding: 16px;
  gap: 12px;
}

.device-top {
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.device-title {
  display: flex;
  align-items: center;
  gap: 10px;
  font-weight: 600;
}

.device-icon-container {
  width: 32px;
  height: 32px;
  background-color: var(--btn-flat-bg);
  border-radius: var(--radius-sm);
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--text-secondary);
}

.device-key-container {
  background-color: var(--bg-primary);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-sm);
  padding: 8px 12px;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.device-key-masked {
  font-family: monospace;
  font-size: 13px;
  color: var(--text-secondary);
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
  max-width: 75%;
}

.device-actions {
  display: flex;
  justify-content: flex-end;
  gap: 8px;
}

/* Help & Instructions Step Cards */
.faq-section {
  display: flex;
  flex-direction: column;
  gap: 14px;
}

.step-card {
  display: flex;
  background-color: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  padding: 16px;
  gap: 16px;
}

.step-num {
  width: 28px;
  height: 28px;
  border-radius: 50%;
  background-color: var(--accent-blue);
  color: #FFFFFF;
  font-weight: 700;
  display: flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
  font-size: 14px;
}

.step-body {
  display: flex;
  flex-direction: column;
  gap: 6px;
}

.step-body h4 {
  font-size: 15px;
  font-weight: 600;
}

.step-body p {
  font-size: 13px;
  color: var(--text-secondary);
}

.step-body ul {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 6px;
  margin-top: 6px;
}

.step-body li {
  font-size: 13px;
  color: var(--text-secondary);
  position: relative;
  padding-left: 14px;
}

.step-body li::before {
  content: "•";
  color: var(--accent-blue);
  position: absolute;
  left: 2px;
  font-weight: 700;
}

.client-links {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 8px;
  margin-top: 8px;
}

.client-link-btn {
  background-color: var(--btn-flat-bg);
  border: 1px solid var(--border-color);
  color: var(--text-main);
  padding: 8px;
  border-radius: var(--radius-sm);
  text-decoration: none;
  font-size: 12px;
  font-weight: 600;
  text-align: center;
  transition: background-color var(--transition-speed);
}

.client-link-btn:hover {
  background-color: var(--btn-flat-hover);
}

/* Modals & Dialogs (Flat design style) */
.flat-modal {
  border: 1px solid var(--border-color);
  background-color: var(--bg-modal);
  color: var(--text-main);
  border-radius: var(--radius-lg);
  padding: 24px;
  margin: auto;
  max-width: 90%;
  width: 360px;
}

.flat-modal::backdrop {
  background-color: rgba(0, 0, 0, 0.7);
  backdrop-filter: blur(2px);
}

.modal-content {
  display: flex;
  flex-direction: column;
  gap: 16px;
}

.modal-content h3 {
  font-size: 18px;
  font-weight: 600;
}

.modal-description {
  font-size: 13px;
  color: var(--text-secondary);
}

/* Form Styles */
.form-group {
  display: flex;
  flex-direction: column;
  gap: 6px;
}

.form-group label {
  font-size: 12px;
  font-weight: 600;
  color: var(--text-secondary);
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.form-group input {
  font-family: var(--font-family);
  background-color: var(--bg-primary);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-sm);
  padding: 12px;
  color: var(--text-main);
  font-size: 14px;
  transition: border-color var(--transition-speed);
}

.form-group input:focus {
  outline: none;
  border-color: var(--accent-blue);
}

.modal-actions {
  display: flex;
  justify-content: flex-end;
  gap: 10px;
  margin-top: 8px;
}

.modal-actions.full-width {
  flex-direction: column;
  gap: 8px;
}

.modal-actions.full-width .btn {
  width: 100%;
}

/* Quick amount selection for payments */
.quick-amounts {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 8px;
}

.amount-card {
  background-color: var(--bg-primary);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-sm);
  padding: 10px 4px;
  color: var(--text-secondary);
  font-family: var(--font-family);
  font-size: 13px;
  font-weight: 600;
  cursor: pointer;
  text-align: center;
  transition: background-color var(--transition-speed), border-color var(--transition-speed);
}

.amount-card.active {
  border-color: var(--accent-blue);
  color: var(--accent-blue);
  background-color: var(--accent-blue-light);
}

.checkout-summary {
  display: flex;
  justify-content: space-between;
  align-items: center;
  background-color: var(--bg-primary);
  border: 1px solid var(--border-color);
  padding: 12px;
  border-radius: var(--radius-sm);
  font-size: 14px;
}

.summary-value {
  font-weight: 700;
  color: var(--accent-green);
  font-size: 16px;
}

.payment-title-group {
  display: flex;
  align-items: center;
  gap: 10px;
}

.payment-shield-icon {
  font-size: 24px;
}

/* Toast System */
.toast-container {
  position: fixed;
  bottom: 24px;
  left: 50%;
  transform: translateX(-50%);
  z-index: 9999;
  display: flex;
  flex-direction: column;
  gap: 8px;
  width: 90%;
  max-width: 360px;
  pointer-events: none;
}

.toast {
  background-color: #1F2937;
  border: 1px solid #374151;
  color: #FFFFFF;
  padding: 12px 16px;
  border-radius: var(--radius-md);
  font-size: 13px;
  font-weight: 500;
  display: flex;
  align-items: center;
  gap: 10px;
  opacity: 0;
  transform: translateY(20px);
  animation: slideUp 0.3s forwards;
  pointer-events: auto;
}

.toast.success {
  border-color: rgba(16, 185, 129, 0.4);
}

.toast-success-icon {
  color: var(--accent-green);
  font-weight: 700;
}

@keyframes slideUp {
  to {
    opacity: 1;
    transform: translateY(0);
  }
}