/* === Variables === */
:root {
  --color-bg: #0f0f13;
  --color-surface: #1a1a24;
  --color-border: #2a2a3a;
  --color-text: #e4e4eb;
  --color-text-muted: #8888a0;
  --color-accent: #4f46e5;
  --color-accent-hover: #4338ca;
  --color-success: #22c55e;
  --color-warning: #f59e0b;
  --color-danger: #ef4444;
  --font: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
  --radius: 8px;
  --radius-lg: 12px;
  --max-width: 1080px;
  --max-width-sm: 560px;
}

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

body {
  font-family: var(--font);
  background: var(--color-bg);
  color: var(--color-text);
  line-height: 1.6;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

main { flex: 1; }

a { color: var(--color-accent); text-decoration: none; }
a:hover { text-decoration: underline; }

img { max-width: 100%; }

/* === Layout === */
.container { max-width: var(--max-width); margin: 0 auto; padding: 0 1.5rem; }
.container-sm { max-width: var(--max-width-sm); }

/* === Header === */
.site-header {
  border-bottom: 1px solid var(--color-border);
  padding: 1rem 0;
}
.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
}
.logo {
  font-size: 1.25rem;
  font-weight: 700;
  color: var(--color-text);
  letter-spacing: -0.02em;
  display: flex;
  align-items: center;
  gap: 0.4rem;
}
.logo:hover { text-decoration: none; color: var(--color-accent); }
.site-header nav a {
  color: var(--color-text-muted);
  font-size: 0.875rem;
  font-weight: 500;
}
.site-header nav a:hover { color: var(--color-text); text-decoration: none; }

/* === Footer === */
.site-footer {
  border-top: 1px solid var(--color-border);
  padding: 2rem 0;
  text-align: center;
  color: var(--color-text-muted);
  font-size: 0.8125rem;
  margin-top: 4rem;
}

/* === Buttons === */
.btn {
  display: inline-block;
  padding: 0.625rem 1.5rem;
  background: var(--color-accent);
  color: #fff;
  border: none;
  border-radius: var(--radius);
  font-family: var(--font);
  font-size: 0.875rem;
  font-weight: 600;
  cursor: pointer;
  transition: background 0.15s;
  text-align: center;
}
.btn:hover { background: var(--color-accent-hover); text-decoration: none; }
.btn-lg { padding: 0.875rem 2rem; font-size: 1rem; }
.btn-block { display: block; width: 100%; }
.btn-secondary {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
}
.btn-secondary:hover { background: var(--color-border); }

/* === Hero === */
.hero {
  text-align: center;
  padding: 6rem 1rem 4rem;
}
.hero h1 {
  font-size: 3rem;
  font-weight: 700;
  letter-spacing: -0.03em;
  margin-bottom: 1rem;
  background: linear-gradient(135deg, var(--color-text), var(--color-accent));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}
.hero-subtitle {
  font-size: 1.125rem;
  color: var(--color-text-muted);
  max-width: 540px;
  margin: 0 auto 2rem;
  line-height: 1.7;
}

/* === How It Works === */
.how-it-works {
  padding: 3rem 0 5rem;
}
.how-it-works h2 {
  text-align: center;
  font-size: 1.5rem;
  margin-bottom: 2.5rem;
  font-weight: 600;
}
.steps {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 2rem;
}
.step {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: 2rem 1.5rem;
  text-align: center;
}
.step-number {
  width: 2.5rem;
  height: 2.5rem;
  background: var(--color-accent);
  color: #fff;
  border-radius: 50%;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  font-weight: 700;
  font-size: 1rem;
  margin-bottom: 1rem;
}
.step h3 { font-size: 1rem; margin-bottom: 0.5rem; }
.step p { font-size: 0.875rem; color: var(--color-text-muted); }

/* === Form === */
.form-page { padding: 3rem 0; }
.form-page h1 {
  font-size: 1.75rem;
  margin-bottom: 2rem;
  font-weight: 600;
}
.invoice-form { display: flex; flex-direction: column; gap: 1.25rem; }

.form-group { display: flex; flex-direction: column; gap: 0.375rem; }
.form-group label {
  font-size: 0.8125rem;
  font-weight: 500;
  color: var(--color-text-muted);
}
.form-group input,
.form-group select {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  padding: 0.75rem 1rem;
  color: var(--color-text);
  font-family: var(--font);
  font-size: 0.9375rem;
}
.form-group input:focus,
.form-group select:focus {
  outline: none;
  border-color: var(--color-accent);
}
.form-row {
  display: grid;
  grid-template-columns: 1fr auto;
  gap: 1rem;
}
.form-row .form-group:last-child select { min-width: 100px; }

.btc-preview {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  padding: 0.75rem 1rem;
  display: flex;
  justify-content: space-between;
  align-items: center;
}
.btc-preview-label { font-size: 0.8125rem; color: var(--color-text-muted); }
.btc-preview-value { font-weight: 600; font-family: monospace; }

.form-error {
  background: rgba(239, 68, 68, 0.1);
  border: 1px solid var(--color-danger);
  border-radius: var(--radius);
  padding: 0.75rem 1rem;
  color: var(--color-danger);
  font-size: 0.875rem;
}

/* === Invoice Page === */
.invoice-page { padding: 3rem 0; }
.invoice-card {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: 2rem;
}
.invoice-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 1.5rem;
}
.invoice-header h1 { font-size: 1.5rem; font-weight: 600; }

.badge {
  display: inline-block;
  padding: 0.25rem 0.75rem;
  border-radius: 999px;
  font-size: 0.75rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.05em;
}
.badge-pending { background: rgba(245,158,11,0.15); color: var(--color-warning); }
.badge-paid, .badge-paid_late { background: rgba(34,197,94,0.15); color: var(--color-success); }
.badge-expired { background: rgba(239,68,68,0.15); color: var(--color-danger); }

.invoice-meta { margin-bottom: 1.5rem; }
.meta-row {
  display: flex;
  justify-content: space-between;
  padding: 0.5rem 0;
  border-bottom: 1px solid var(--color-border);
  font-size: 0.875rem;
}
.meta-label { color: var(--color-text-muted); }
.meta-value { font-weight: 500; }

.invoice-amount {
  text-align: center;
  padding: 1.5rem 0;
}
.btc-amount {
  font-size: 2rem;
  font-weight: 700;
  font-family: monospace;
  letter-spacing: -0.02em;
}
.sats-amount {
  font-size: 0.875rem;
  color: var(--color-text-muted);
  margin-top: 0.25rem;
}

.qr-section { text-align: center; padding: 1.5rem 0; }
.qr-image {
  width: 220px;
  height: 220px;
  border-radius: var(--radius);
  background: #fff;
  padding: 8px;
}
.bip21-uri {
  margin-top: 0.75rem;
}
.bip21-uri code {
  font-size: 0.7rem;
  color: var(--color-text-muted);
  word-break: break-all;
}

.timer-section {
  text-align: center;
  padding: 1rem 0;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
}
.timer-label { font-size: 0.875rem; color: var(--color-text-muted); }
.timer-value {
  font-size: 1.25rem;
  font-weight: 700;
  font-family: monospace;
  color: var(--color-warning);
}
.timer-value.expired { color: var(--color-danger); }

.paid-section {
  text-align: center;
  padding: 2rem 0;
}
.paid-checkmark {
  width: 3.5rem;
  height: 3.5rem;
  background: rgba(34,197,94,0.15);
  color: var(--color-success);
  border-radius: 50%;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  font-size: 1.75rem;
  margin-bottom: 0.75rem;
}
.paid-section p { color: var(--color-text-muted); font-size: 0.875rem; }

.invoice-actions {
  display: flex;
  gap: 0.75rem;
  margin-top: 1.5rem;
}
.invoice-actions .btn { flex: 1; }

/* === Nav Links === */
.nav-links { display: flex; align-items: center; gap: 1.25rem; }
.lang-toggle {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 0.2rem 0.6rem;
  border: 1px solid var(--color-border);
  border-radius: 999px;
  font-size: 0.75rem;
  font-weight: 600;
  letter-spacing: 0.04em;
  color: var(--color-text-muted);
  transition: border-color 0.15s, color 0.15s;
}
.lang-toggle:hover { border-color: var(--color-accent); color: var(--color-text); text-decoration: none; }

/* === Dashboard === */
.dashboard-page { padding: 3rem 0; }
.dashboard-page h1 { font-size: 1.75rem; font-weight: 600; margin-bottom: 2rem; }
.dashboard-section { margin-top: 2.5rem; }
.dashboard-section h2 { font-size: 1.25rem; font-weight: 600; margin-bottom: 1rem; }

.stats-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
  gap: 1rem;
}
.stat-card {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: 1.5rem;
}
.stat-label { font-size: 0.8125rem; color: var(--color-text-muted); margin-bottom: 0.375rem; }
.stat-value { font-size: 1.5rem; font-weight: 700; font-family: monospace; }

/* === Data Table === */
.table-wrap { overflow-x: auto; }
.data-table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.875rem;
}
.data-table th,
.data-table td {
  padding: 0.75rem 1rem;
  text-align: left;
  border-bottom: 1px solid var(--color-border);
}
.data-table th {
  color: var(--color-text-muted);
  font-weight: 500;
  font-size: 0.75rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
}
.data-table td.mono { font-family: monospace; }
.data-table td.text-muted { color: var(--color-text-muted); }

/* === Activity List === */
.activity-list { list-style: none; }
.activity-item {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 0.625rem 0;
  border-bottom: 1px solid var(--color-border);
  font-size: 0.875rem;
}
.activity-type { text-transform: capitalize; }
.activity-time { font-size: 0.75rem; }
.text-muted { color: var(--color-text-muted); }

.empty-state {
  color: var(--color-text-muted);
  font-size: 0.875rem;
  padding: 1.5rem 0;
}

/* === Responsive === */
@media (max-width: 640px) {
  .hero h1 { font-size: 2rem; }
  .hero { padding: 4rem 1rem 3rem; }
  .steps { grid-template-columns: 1fr; }
  .form-row { grid-template-columns: 1fr 1fr; }
  .invoice-card { padding: 1.5rem; }
  .invoice-actions { flex-direction: column; }
  .qr-image { width: 180px; height: 180px; }
  .stats-grid { grid-template-columns: 1fr; }
  .nav-links { gap: 0.75rem; }
  .nav-links a { font-size: 0.8125rem; }
}