:root {
    --primary: #2563eb;
    --primary-dark: #1d4ed8;
    --danger: #ef4444;
    --success: #22c55e;
    --warning: #f59e0b;
    --gray-50: #f8fafc;
    --gray-100: #f1f5f9;
    --gray-200: #e2e8f0;
    --gray-300: #cbd5e1;
    --gray-500: #64748b;
    --gray-700: #334155;
    --gray-900: #0f172a;
    --radius: 6px;
}

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

body { font-family: system-ui, -apple-system, sans-serif; background: var(--gray-50); color: var(--gray-700); line-height: 1.5; }

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

/* Navbar */
.navbar { display: flex; align-items: center; justify-content: space-between; background: var(--gray-900); padding: 0 24px; height: 52px; }
.nav-brand a { color: #fff; font-weight: 700; font-size: 18px; text-decoration: none; }
.nav-links { display: flex; gap: 4px; }
.nav-links a { color: var(--gray-300); padding: 6px 14px; border-radius: var(--radius); font-size: 14px; text-decoration: none; transition: background .15s; }
.nav-links a:hover { background: rgba(255,255,255,.1); color: #fff; }

/* Container */
.container { max-width: 1100px; margin: 0 auto; padding: 28px 24px; }

/* Headings */
h1 { font-size: 24px; color: var(--gray-900); margin-bottom: 20px; }
h2 { font-size: 18px; color: var(--gray-900); margin-bottom: 12px; }
h3 { font-size: 16px; color: var(--gray-700); margin-bottom: 10px; }

/* Alerts */
.alert { padding: 12px 16px; border-radius: var(--radius); margin-bottom: 16px; font-size: 14px; }
.alert-success { background: #dcfce7; color: #166534; border-left: 4px solid var(--success); }
.alert-error { background: #fef2f2; color: #991b1b; border-left: 4px solid var(--danger); }

/* Buttons */
.btn { display: inline-block; padding: 8px 18px; border: 1px solid var(--gray-200); background: #fff; color: var(--gray-700); border-radius: var(--radius); font-size: 14px; cursor: pointer; text-decoration: none; transition: all .15s; line-height: 1.4; }
.btn:hover { background: var(--gray-100); text-decoration: none; }
.btn-primary { background: var(--primary); color: #fff; border-color: var(--primary); }
.btn-primary:hover { background: var(--primary-dark); }
.btn-danger { color: var(--danger); border-color: #fecaca; }
.btn-danger:hover { background: #fef2f2; }
.btn-sm { padding: 4px 10px; font-size: 13px; }
.btn-block { display: block; width: 100%; text-align: center; }
.btn-active { background: var(--primary); color: #fff; border-color: var(--primary); }

/* Forms */
.form-card { background: #fff; padding: 24px; border-radius: 8px; border: 1px solid var(--gray-200); }
.form-group { margin-bottom: 16px; flex: 1; }
.form-group label { display: block; font-size: 13px; font-weight: 600; color: var(--gray-700); margin-bottom: 4px; }
.form-group input, .form-group select, .form-group textarea { width: 100%; padding: 8px 12px; border: 1px solid var(--gray-200); border-radius: var(--radius); font-size: 14px; color: var(--gray-900); background: #fff; }
.form-group input:focus, .form-group select:focus, .form-group textarea:focus { outline: none; border-color: var(--primary); box-shadow: 0 0 0 3px rgba(37,99,235,.1); }
.form-group textarea { resize: vertical; }
.form-row { display: flex; gap: 16px; }
.form-row .flex-2 { flex: 2; }
.form-actions { display: flex; gap: 10px; margin-top: 20px; }
.auth-form { max-width: 400px; margin: 60px auto; }
.auth-form h1 { text-align: center; }
.text-center { text-align: center; margin-top: 16px; font-size: 14px; }

/* Tables */
.table { width: 100%; border-collapse: collapse; background: #fff; border-radius: 8px; overflow: hidden; border: 1px solid var(--gray-200); }
.table th { padding: 10px 14px; text-align: left; background: var(--gray-50); font-size: 12px; text-transform: uppercase; color: var(--gray-500); font-weight: 600; border-bottom: 2px solid var(--gray-200); }
.table td { padding: 10px 14px; border-bottom: 1px solid var(--gray-100); font-size: 14px; }
.table tbody tr:hover { background: var(--gray-50); }
.table .actions { white-space: nowrap; display: flex; gap: 4px; }

/* Invoice lines table */
.table-lines input { width: 100%; padding: 6px 8px; border: 1px solid var(--gray-200); border-radius: 4px; font-size: 13px; }
.table-lines input:focus { outline: none; border-color: var(--primary); }
.line-total { font-weight: 600; white-space: nowrap; min-width: 90px; }

/* Invoice totals */
.invoice-totals { margin: 20px 0; padding: 16px; background: var(--gray-50); border-radius: var(--radius); text-align: right; font-size: 14px; }
.invoice-totals div { margin-bottom: 6px; }
.invoice-totals .total-line { font-size: 18px; color: var(--primary); border-top: 2px solid var(--gray-200); padding-top: 10px; margin-top: 10px; }

/* Stats grid */
.stats-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(200px, 1fr)); gap: 16px; margin-bottom: 28px; }
.stat-card { background: #fff; padding: 20px; border-radius: 8px; border: 1px solid var(--gray-200); text-align: center; }
.stat-number { font-size: 28px; font-weight: 700; color: var(--primary); }
.stat-label { font-size: 13px; color: var(--gray-500); margin-top: 4px; }

/* Section header */
.section-header { display: flex; justify-content: space-between; align-items: center; margin-bottom: 20px; }
.section-header h1, .section-header h2 { margin-bottom: 0; }

/* Badges */
.badge { display: inline-block; padding: 3px 10px; border-radius: 12px; font-size: 12px; font-weight: 600; }
.badge-draft { background: #fef3c7; color: #92400e; }
.badge-sent { background: #dbeafe; color: #1e40af; }
.badge-paid { background: #dcfce7; color: #166534; }
.badge-cancelled { background: #fee2e2; color: #991b1b; }

/* Filters */
.filters { display: flex; gap: 6px; margin-bottom: 20px; flex-wrap: wrap; }

/* Misc */
.text-muted { color: var(--gray-500); font-size: 14px; }
code { background: var(--gray-100); padding: 2px 6px; border-radius: 3px; font-size: 13px; }

/* Hero */
.hero { text-align: center; padding: 80px 20px; }
.hero h1 { font-size: 36px; margin-bottom: 12px; }
.hero p { font-size: 18px; color: var(--gray-500); margin-bottom: 28px; }
.hero-actions { display: flex; gap: 12px; justify-content: center; }

/* Responsive */
@media (max-width: 768px) {
    .form-row { flex-direction: column; gap: 0; }
    .stats-grid { grid-template-columns: repeat(2, 1fr); }
    .table { font-size: 13px; }
    .table .actions { flex-direction: column; }
    .nav-links { gap: 0; }
    .nav-links a { padding: 6px 8px; font-size: 13px; }
}