:root {
    --primary: #00bcd4;
    --primary-dark: #00838f;
    --primary-light: #b2ebf2;
    --success: #4caf50;
    --warning: #ff9800;
    --danger: #f44336;
    --info: #2196f3;
    --dark: #263238;
    --gray-100: #f5f7fa;
    --gray-200: #e8ecef;
    --gray-300: #cfd8dc;
    --gray-400: #90a4ae;
    --gray-500: #607d8b;
    --white: #ffffff;
    --shadow: 0 2px 10px rgba(0,0,0,0.08);
    --radius: 12px;
}

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

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
    background: var(--gray-100);
    color: var(--dark);
}

.app-container { display: flex; min-height: 100vh; }

.sidebar {
    width: 70px;
    background: var(--white);
    border-right: 1px solid var(--gray-200);
    display: flex;
    flex-direction: column;
    align-items: center;
    padding: 20px 0;
    position: fixed;
    height: 100vh;
}

.sidebar-logo {
    width: 45px; height: 45px;
    background: linear-gradient(135deg, var(--primary), var(--primary-dark));
    border-radius: var(--radius);
    display: flex; align-items: center; justify-content: center;
    color: var(--white); font-size: 20px; margin-bottom: 30px;
}

.sidebar-nav { display: flex; flex-direction: column; gap: 8px; flex: 1; }

.nav-item {
    width: 45px; height: 45px; border-radius: var(--radius);
    display: flex; align-items: center; justify-content: center;
    color: var(--gray-400); text-decoration: none; transition: all 0.3s;
}

.nav-item:hover { background: var(--gray-100); color: var(--primary); }
.nav-item.active { background: var(--primary-light); color: var(--primary); }

.main-content { flex: 1; margin-left: 70px; display: flex; flex-direction: column; }

.main-header {
    background: var(--white);
    padding: 15px 30px;
    display: flex; align-items: center; justify-content: space-between;
    border-bottom: 1px solid var(--gray-200);
    flex-wrap: wrap; gap: 15px;
}

.header-title h1 { font-size: 22px; font-weight: 600; }
.text-primary { color: var(--primary); }

.header-stats { display: flex; gap: 15px; }

.stat-box {
    background: var(--gray-100);
    padding: 10px 20px;
    border-radius: var(--radius);
    text-align: center;
    min-width: 100px;
}

.stat-box.success { background: #e8f5e9; }
.stat-box.warning { background: #fff3e0; }
.stat-box.info { background: #e3f2fd; }

.stat-label { font-size: 11px; color: var(--gray-500); text-transform: uppercase; display: block; }
.stat-value { font-size: 16px; font-weight: 700; color: var(--dark); }

.stat-box.success .stat-value { color: var(--success); }
.stat-box.warning .stat-value { color: var(--warning); }
.stat-box.info .stat-value { color: var(--info); }

.content-area { display: flex; flex: 1; padding: 20px; gap: 20px; overflow: hidden; }

.invoice-list-section {
    width: 400px; flex-shrink: 0; background: var(--white);
    border-radius: var(--radius); box-shadow: var(--shadow);
    display: flex; flex-direction: column; overflow: hidden;
}

.section-header {
    padding: 15px 20px;
    display: flex; align-items: center; justify-content: space-between;
    border-bottom: 1px solid var(--gray-200);
    gap: 10px; flex-wrap: wrap;
}

.filter-row { display: flex; gap: 10px; align-items: center; flex: 1; }

.search-box {
    display: flex; align-items: center; gap: 8px;
    background: var(--gray-100);
    padding: 8px 12px;
    border-radius: 8px;
    flex: 1;
}

.search-box i { color: var(--gray-400); }
.search-box input {
    border: none; background: none; outline: none;
    font-size: 14px; width: 100%;
}

.filter-select {
    padding: 8px 12px; border: 1px solid var(--gray-300);
    border-radius: 8px; font-size: 14px; background: var(--white); cursor: pointer;
}

.btn {
    padding: 10px 20px; border: none; border-radius: 8px;
    font-size: 14px; font-weight: 500; cursor: pointer;
    display: inline-flex; align-items: center; gap: 8px; transition: all 0.3s;
}

.btn-primary { background: var(--primary); color: var(--white); }
.btn-primary:hover { background: var(--primary-dark); }
.btn-secondary { background: var(--gray-200); color: var(--dark); }
.btn-secondary:hover { background: var(--gray-300); }
.btn-danger { background: var(--danger); color: var(--white); }
.btn-danger:hover { background: #d32f2f; }
.btn-sm { padding: 6px 12px; font-size: 12px; }
.btn-sm.active { background: var(--primary); color: var(--white); }

.invoice-list { flex: 1; overflow-y: auto; }

.invoice-item {
    padding: 15px 20px; border-bottom: 1px solid var(--gray-200);
    cursor: pointer; transition: all 0.3s;
}

.invoice-item:hover { background: var(--gray-100); }
.invoice-item.active { background: var(--primary-light); border-left: 3px solid var(--primary); }

.invoice-item-header { display: flex; justify-content: space-between; margin-bottom: 5px; }
.invoice-client { font-weight: 600; }
.invoice-amount { font-weight: 600; }
.invoice-meta { font-size: 13px; color: var(--gray-500); }
.invoice-number { color: var(--primary); }

.status-badge {
    font-size: 11px; padding: 3px 10px; border-radius: 20px;
    font-weight: 500; text-transform: uppercase;
}

.status-draft { background: var(--gray-200); color: var(--gray-500); }
.status-sent { background: #e3f2fd; color: #1976d2; }
.status-paid { background: #e8f5e9; color: #388e3c; }
.status-overdue { background: #ffebee; color: #d32f2f; }

.invoice-detail-section {
    flex: 1; background: var(--white); border-radius: var(--radius);
    box-shadow: var(--shadow); overflow-y: auto;
}

.detail-placeholder {
    height: 100%; display: flex; flex-direction: column;
    align-items: center; justify-content: center; color: var(--gray-400);
}

.detail-placeholder i { font-size: 60px; margin-bottom: 15px; }

.invoice-detail-header {
    padding: 15px 25px; border-bottom: 1px solid var(--gray-200);
    display: flex; justify-content: space-between; align-items: center;
    flex-wrap: wrap; gap: 10px;
}

.detail-actions { display: flex; gap: 8px; flex-wrap: wrap; }

.invoice-detail-body { padding: 25px; }

.detail-top { display: flex; justify-content: space-between; margin-bottom: 25px; flex-wrap: wrap; gap: 20px; }
.invoice-info h2 { font-size: 24px; margin-bottom: 10px; color: var(--dark); }
.invoice-info-row { display: flex; gap: 10px; font-size: 14px; color: var(--gray-500); margin-bottom: 5px; }
.invoice-info-row span:first-child { min-width: 140px; }
.company-info { text-align: right; }
.company-logo { font-size: 20px; font-weight: 700; color: var(--primary); margin-bottom: 5px; }
.company-address { font-size: 13px; color: var(--gray-500); line-height: 1.5; }

.detail-middle { display: grid; grid-template-columns: repeat(3, 1fr); gap: 15px; margin-bottom: 25px; }

.info-card { background: var(--gray-100); padding: 15px; border-radius: 8px; }
.info-card-label { font-size: 11px; color: var(--gray-500); text-transform: uppercase; margin-bottom: 5px; }
.info-card-value { font-size: 18px; font-weight: 600; }
.info-card-sub { font-size: 12px; color: var(--gray-500); margin-top: 5px; }

.items-table { width: 100%; border-collapse: collapse; margin-bottom: 20px; }
.items-table th {
    text-align: left; padding: 12px; background: var(--gray-100);
    font-size: 12px; font-weight: 600; color: var(--gray-500); text-transform: uppercase;
}
.items-table td { padding: 12px; border-bottom: 1px solid var(--gray-200); }
.items-table input, .items-table select {
    width: 100%; padding: 8px; border: 1px solid var(--gray-300); border-radius: 6px; font-size: 14px;
}

.detail-totals { display: flex; justify-content: flex-end; margin-top: 20px; }
.totals-table { width: 280px; }
.totals-row { display: flex; justify-content: space-between; padding: 8px 0; border-bottom: 1px solid var(--gray-200); }
.totals-row.total-final { font-size: 18px; font-weight: 700; border-bottom: none; padding-top: 15px; }

.invoice-notes { margin-top: 20px; padding: 15px; background: #fffde7; border-left: 3px solid #ffc107; border-radius: 0 8px 8px 0; }

.status-actions { margin-top: 25px; padding-top: 20px; border-top: 1px solid var(--gray-200); display: flex; align-items: center; gap: 10px; flex-wrap: wrap; }
.status-actions span { color: var(--gray-500); font-size: 14px; }

.clients-list { display: flex; flex-direction: column; gap: 10px; }
.client-item {
    display: flex; justify-content: space-between; align-items: center;
    padding: 15px; background: var(--gray-100); border-radius: 8px;
}
.client-info { flex: 1; }
.client-info strong { display: block; margin-bottom: 3px; }
.client-info span { display: block; font-size: 13px; color: var(--gray-500); }
.client-actions { display: flex; gap: 5px; }

.modal {
    display: none; position: fixed; top: 0; left: 0; width: 100%; height: 100%;
    background: rgba(0,0,0,0.5); z-index: 1000; align-items: center; justify-content: center; padding: 20px;
}
.modal.active { display: flex; }

.modal-content {
    background: var(--white); border-radius: var(--radius); width: 100%; max-width: 500px;
    max-height: 90vh; display: flex; flex-direction: column; box-shadow: var(--shadow);
}
.modal-content.modal-large { max-width: 800px; }

.modal-header {
    padding: 20px 25px; border-bottom: 1px solid var(--gray-200);
    display: flex; justify-content: space-between; align-items: center;
}
.modal-header h2 { font-size: 20px; }

.close-btn { background: none; border: none; font-size: 28px; color: var(--gray-400); cursor: pointer; }
.modal-body { padding: 25px; overflow-y: auto; flex: 1; }
.modal-footer { padding: 15px 25px; border-top: 1px solid var(--gray-200); display: flex; justify-content: flex-end; gap: 10px; }

.form-group { margin-bottom: 15px; }
.form-group label { display: block; font-size: 13px; font-weight: 500; margin-bottom: 5px; }
.form-group input, .form-group select, .form-group textarea {
    width: 100%; padding: 10px 12px; border: 1px solid var(--gray-300);
    border-radius: 8px; font-size: 14px;
}
.form-group input:focus, .form-group select:focus { outline: none; border-color: var(--primary); }

.form-row { display: flex; gap: 15px; }
.form-row .form-group { flex: 1; }

.toast {
    position: fixed; bottom: 30px; right: 30px; background: var(--dark); color: var(--white);
    padding: 15px 25px; border-radius: 8px; display: flex; align-items: center; gap: 10px;
    transform: translateY(100px); opacity: 0; transition: all 0.3s; z-index: 2000;
}
.toast.show { transform: translateY(0); opacity: 1; }
.toast.success { background: var(--success); }
.toast.error { background: var(--danger); }

.loading { display: flex; flex-direction: column; align-items: center; justify-content: center; padding: 40px; color: var(--gray-400); }

@media (max-width: 1200px) {
    .content-area { flex-direction: column; }
    .invoice-list-section { width: 100%; max-height: 350px; }
    .detail-middle { grid-template-columns: 1fr 1fr; }
    .header-stats { display: none; }
}

@media (max-width: 768px) {
    .sidebar { width: 60px; }
    .main-content { margin-left: 60px; }
    .detail-middle { grid-template-columns: 1fr; }
    .detail-top { flex-direction: column; }
    .company-info { text-align: left; }
}