/* CSS Variables */
:root {
    --primary-color: #2563eb;
    --primary-hover: #1d4ed8;
    --primary-light: #dbeafe;
    --secondary-color: #64748b;
    --success-color: #10b981;
    --warning-color: #f59e0b;
    --danger-color: #ef4444;
    --background: #f8fafc;
    --surface: #ffffff;
    --text-primary: #1e293b;
    --text-secondary: #64748b;
    --border-color: #e2e8f0;
    --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.05);
    --shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
    --radius: 8px;
    --radius-lg: 12px;
    --sidebar-width: 260px;
    --header-height: 64px;
    --transition: all 0.2s ease;
}

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

html {
    font-size: 16px;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, sans-serif;
    background: var(--background);
    color: var(--text-primary);
    line-height: 1.5;
    min-height: 100vh;
}

/* App Layout */
.app-container {
    display: flex;
    min-height: 100vh;
}

/* Sidebar */
.sidebar {
    width: var(--sidebar-width);
    background: var(--surface);
    border-right: 1px solid var(--border-color);
    position: fixed;
    top: 0;
    left: 0;
    height: 100vh;
    z-index: 100;
    display: flex;
    flex-direction: column;
    transition: var(--transition);
}

.sidebar-header {
    padding: 1.25rem;
    display: flex;
    align-items: center;
    justify-content: space-between;
    border-bottom: 1px solid var(--border-color);
}

.logo {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    font-weight: 700;
    font-size: 1.25rem;
    color: var(--primary-color);
}

.logo svg {
    width: 32px;
    height: 32px;
}

.sidebar-toggle {
    display: none;
    background: none;
    border: none;
    cursor: pointer;
    padding: 0.5rem;
    color: var(--text-secondary);
}

.sidebar-toggle svg {
    width: 24px;
    height: 24px;
}

.sidebar-nav {
    flex: 1;
    padding: 1rem 0;
    overflow-y: auto;
}

.nav-item {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    padding: 0.875rem 1.25rem;
    color: var(--text-secondary);
    text-decoration: none;
    font-weight: 500;
    transition: var(--transition);
    border-left: 3px solid transparent;
}

.nav-item svg {
    width: 20px;
    height: 20px;
    flex-shrink: 0;
}

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

.nav-item.active {
    background: var(--primary-light);
    color: var(--primary-color);
    border-left-color: var(--primary-color);
}

/* Main Content */
.main-content {
    flex: 1;
    margin-left: var(--sidebar-width);
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

.top-header {
    height: var(--header-height);
    background: var(--surface);
    border-bottom: 1px solid var(--border-color);
    padding: 0 1.5rem;
    display: flex;
    align-items: center;
    justify-content: space-between;
    position: sticky;
    top: 0;
    z-index: 50;
}

.mobile-menu-btn {
    display: none;
    background: none;
    border: none;
    cursor: pointer;
    padding: 0.5rem;
    color: var(--text-secondary);
}

.mobile-menu-btn svg {
    width: 24px;
    height: 24px;
}

.page-title {
    font-size: 1.25rem;
    font-weight: 600;
}

.header-actions {
    display: flex;
    align-items: center;
    gap: 1rem;
}

.current-date {
    color: var(--text-secondary);
    font-size: 0.875rem;
}

.content-area {
    flex: 1;
    padding: 1.5rem;
}

/* Sections */
.section {
    display: none;
}

.section.active {
    display: block;
    animation: fadeIn 0.3s ease;
}

@keyframes fadeIn {
    from { opacity: 0; transform: translateY(10px); }
    to { opacity: 1; transform: translateY(0); }
}

.section-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    margin-bottom: 1.5rem;
    flex-wrap: wrap;
    gap: 1rem;
}

.section-header h2 {
    font-size: 1.5rem;
    font-weight: 600;
}

/* Stats Grid */
.stats-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
    gap: 1.5rem;
    margin-bottom: 1.5rem;
}

.stat-card {
    background: var(--surface);
    border-radius: var(--radius-lg);
    padding: 1.5rem;
    display: flex;
    align-items: center;
    gap: 1rem;
    box-shadow: var(--shadow-sm);
    border: 1px solid var(--border-color);
    transition: var(--transition);
}

.stat-card:hover {
    box-shadow: var(--shadow);
    transform: translateY(-2px);
}

.stat-icon {
    width: 56px;
    height: 56px;
    border-radius: var(--radius);
    display: flex;
    align-items: center;
    justify-content: center;
}

.stat-icon svg {
    width: 28px;
    height: 28px;
}

.stat-icon.sales {
    background: #dcfce7;
    color: #16a34a;
}

.stat-icon.invoices {
    background: #dbeafe;
    color: #2563eb;
}

.stat-icon.customers {
    background: #fef3c7;
    color: #d97706;
}

.stat-icon.products {
    background: #f3e8ff;
    color: #9333ea;
}

.stat-info h3 {
    font-size: 0.875rem;
    color: var(--text-secondary);
    font-weight: 500;
    margin-bottom: 0.25rem;
}

.stat-value {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--text-primary);
}

/* Dashboard Grid */
.dashboard-grid {
    display: grid;
    grid-template-columns: 2fr 1fr;
    gap: 1.5rem;
}

/* Cards */
.card {
    background: var(--surface);
    border-radius: var(--radius-lg);
    border: 1px solid var(--border-color);
    box-shadow: var(--shadow-sm);
    overflow: hidden;
}

.card-header {
    padding: 1rem 1.5rem;
    border-bottom: 1px solid var(--border-color);
    display: flex;
    align-items: center;
    justify-content: space-between;
}

.card-header h2 {
    font-size: 1rem;
    font-weight: 600;
}

.card-body {
    padding: 1.5rem;
}

.view-all {
    color: var(--primary-color);
    text-decoration: none;
    font-size: 0.875rem;
    font-weight: 500;
}

.view-all:hover {
    text-decoration: underline;
}

/* Payment Summary */
.payment-stat {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 0.75rem 0;
    border-bottom: 1px solid var(--border-color);
}

.payment-stat:last-child {
    border-bottom: none;
}

.payment-stat .label {
    color: var(--text-secondary);
}

.payment-stat .value {
    font-weight: 600;
}

.payment-stat .value.paid { color: var(--success-color); }
.payment-stat .value.pending { color: var(--warning-color); }
.payment-stat .value.overdue { color: var(--danger-color); }

/* Tables */
.table-responsive {
    overflow-x: auto;
}

.data-table {
    width: 100%;
    border-collapse: collapse;
}

.data-table th,
.data-table td {
    padding: 0.875rem 1rem;
    text-align: left;
    border-bottom: 1px solid var(--border-color);
}

.data-table th {
    background: var(--background);
    font-weight: 600;
    font-size: 0.875rem;
    color: var(--text-secondary);
    white-space: nowrap;
}

.data-table tbody tr:hover {
    background: var(--background);
}

.data-table tbody tr:last-child td {
    border-bottom: none;
}

.empty-state {
    text-align: center;
    color: var(--text-secondary);
    padding: 2rem !important;
}

/* Status Badges */
.status-badge {
    display: inline-flex;
    align-items: center;
    padding: 0.25rem 0.75rem;
    border-radius: 9999px;
    font-size: 0.75rem;
    font-weight: 600;
    text-transform: capitalize;
}

.status-badge.paid {
    background: #dcfce7;
    color: #16a34a;
}

.status-badge.pending {
    background: #fef3c7;
    color: #d97706;
}

.status-badge.overdue {
    background: #fee2e2;
    color: #dc2626;
}

/* Action Buttons */
.action-btns {
    display: flex;
    gap: 0.5rem;
}

.action-btn {
    background: none;
    border: none;
    cursor: pointer;
    padding: 0.375rem;
    border-radius: var(--radius);
    color: var(--text-secondary);
    transition: var(--transition);
}

.action-btn:hover {
    background: var(--background);
    color: var(--primary-color);
}

.action-btn.delete:hover {
    color: var(--danger-color);
}

.action-btn svg {
    width: 18px;
    height: 18px;
}

/* Buttons */
.btn {
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    padding: 0.625rem 1.25rem;
    border-radius: var(--radius);
    font-weight: 500;
    font-size: 0.875rem;
    cursor: pointer;
    border: none;
    transition: var(--transition);
    text-decoration: none;
}

.btn svg {
    width: 18px;
    height: 18px;
}

.btn-primary {
    background: var(--primary-color);
    color: white;
}

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

.btn-secondary {
    background: var(--background);
    color: var(--text-primary);
    border: 1px solid var(--border-color);
}

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

.btn-danger {
    background: var(--danger-color);
    color: white;
}

.btn-danger:hover {
    background: #dc2626;
}

/* Forms */
.form-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 1.5rem;
}

.form-grid .full-width {
    grid-column: span 2;
}

.form-row {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 1rem;
}

.form-group {
    margin-bottom: 1rem;
}

.form-group:last-child {
    margin-bottom: 0;
}

.form-group label {
    display: block;
    margin-bottom: 0.5rem;
    font-weight: 500;
    font-size: 0.875rem;
    color: var(--text-secondary);
}

.form-group input,
.form-group select,
.form-group textarea {
    width: 100%;
    padding: 0.625rem 0.875rem;
    border: 1px solid var(--border-color);
    border-radius: var(--radius);
    font-size: 0.875rem;
    transition: var(--transition);
    background: var(--surface);
}

.form-group input:focus,
.form-group select:focus,
.form-group textarea:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px var(--primary-light);
}

.form-group textarea {
    resize: vertical;
    min-height: 80px;
}

.form-group input[readonly] {
    background: var(--background);
    color: var(--text-secondary);
}

.form-actions {
    display: flex;
    justify-content: flex-end;
    gap: 1rem;
    margin-top: 1.5rem;
}

/* File Upload */
.file-upload {
    position: relative;
}

.file-upload input[type="file"] {
    position: absolute;
    width: 100%;
    height: 100%;
    top: 0;
    left: 0;
    opacity: 0;
    cursor: pointer;
}

.file-preview {
    border: 2px dashed var(--border-color);
    border-radius: var(--radius);
    padding: 2rem;
    text-align: center;
    color: var(--text-secondary);
    transition: var(--transition);
    background-size: contain;
    background-repeat: no-repeat;
    background-position: center;
    min-height: 120px;
    display: flex;
    align-items: center;
    justify-content: center;
}

.file-preview.has-image {
    border-style: solid;
    border-color: var(--primary-color);
}

.file-preview.has-image span {
    display: none;
}

.file-upload:hover .file-preview {
    border-color: var(--primary-color);
    background-color: var(--primary-light);
}

/* Invoice Form */
.invoice-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 1.5rem;
}

.invoice-grid .full-width {
    grid-column: span 2;
}

.items-table input,
.items-table select {
    padding: 0.5rem;
    border: 1px solid var(--border-color);
    border-radius: var(--radius);
    font-size: 0.875rem;
    width: 100%;
}

.items-table .qty-input,
.items-table .discount-input {
    width: 70px;
}

.items-table .price-input {
    width: 100px;
}

.items-table .total-cell {
    font-weight: 600;
    white-space: nowrap;
}

.invoice-summary .summary-row {
    display: flex;
    justify-content: space-between;
    padding: 0.75rem 0;
    border-bottom: 1px solid var(--border-color);
}

.invoice-summary .summary-row:last-child {
    border-bottom: none;
}

.invoice-summary .summary-row.total {
    font-weight: 700;
    font-size: 1.125rem;
    color: var(--primary-color);
}

/* Filter Group */
.filter-group {
    display: flex;
    gap: 1rem;
}

.filter-group select {
    padding: 0.5rem 1rem;
    border: 1px solid var(--border-color);
    border-radius: var(--radius);
    font-size: 0.875rem;
    background: var(--surface);
}

/* Modal */
.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: 1rem;
}

.modal.active {
    display: flex;
    animation: fadeIn 0.2s ease;
}

.modal-content {
    background: var(--surface);
    border-radius: var(--radius-lg);
    width: 100%;
    max-width: 500px;
    max-height: 90vh;
    overflow-y: auto;
    box-shadow: var(--shadow-lg);
}

.modal-content.modal-lg {
    max-width: 800px;
}

.modal-header {
    padding: 1.25rem 1.5rem;
    border-bottom: 1px solid var(--border-color);
    display: flex;
    align-items: center;
    justify-content: space-between;
}

.modal-header h2 {
    font-size: 1.125rem;
    font-weight: 600;
}

.modal-close {
    background: none;
    border: none;
    font-size: 1.5rem;
    cursor: pointer;
    color: var(--text-secondary);
    padding: 0.25rem;
    line-height: 1;
}

.modal-close:hover {
    color: var(--text-primary);
}

.modal-body {
    padding: 1.5rem;
}

.modal-footer {
    padding: 1rem 1.5rem;
    border-top: 1px solid var(--border-color);
    display: flex;
    justify-content: flex-end;
    gap: 0.75rem;
}

/* Invoice Preview */
.invoice-preview {
    background: white;
    padding: 2rem;
    font-size: 0.875rem;
}

.invoice-preview .invoice-header {
    display: flex;
    justify-content: space-between;
    margin-bottom: 2rem;
    padding-bottom: 1rem;
    border-bottom: 2px solid var(--primary-color);
}

.invoice-preview .business-info {
    display: flex;
    gap: 1rem;
}

.invoice-preview .business-logo {
    width: 80px;
    height: 80px;
    object-fit: contain;
}

.invoice-preview .business-details h1 {
    font-size: 1.25rem;
    color: var(--primary-color);
    margin-bottom: 0.5rem;
}

.invoice-preview .business-details p {
    color: var(--text-secondary);
    font-size: 0.8rem;
    line-height: 1.4;
}

.invoice-preview .invoice-title {
    text-align: right;
}

.invoice-preview .invoice-title h2 {
    font-size: 1.5rem;
    color: var(--text-primary);
}

.invoice-preview .invoice-title p {
    color: var(--text-secondary);
    margin-top: 0.5rem;
}

.invoice-preview .invoice-details {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 2rem;
    margin-bottom: 2rem;
}

.invoice-preview .detail-section h3 {
    font-size: 0.75rem;
    text-transform: uppercase;
    color: var(--text-secondary);
    margin-bottom: 0.5rem;
}

.invoice-preview .detail-section p {
    margin-bottom: 0.25rem;
}

.invoice-preview .items-table {
    width: 100%;
    margin-bottom: 2rem;
}

.invoice-preview .items-table th {
    background: var(--primary-color);
    color: white;
    padding: 0.75rem;
    text-align: left;
}

.invoice-preview .items-table td {
    padding: 0.75rem;
    border-bottom: 1px solid var(--border-color);
}

.invoice-preview .invoice-totals {
    display: flex;
    justify-content: flex-end;
}

.invoice-preview .totals-table {
    width: 300px;
}

.invoice-preview .totals-table tr td {
    padding: 0.5rem;
}

.invoice-preview .totals-table tr td:last-child {
    text-align: right;
}

.invoice-preview .totals-table .grand-total {
    font-weight: 700;
    font-size: 1.125rem;
    background: var(--primary-light);
    color: var(--primary-color);
}

.invoice-preview .payment-info {
    margin-top: 2rem;
    padding-top: 1rem;
    border-top: 1px solid var(--border-color);
}

.invoice-preview .payment-info h3 {
    font-size: 0.875rem;
    margin-bottom: 0.5rem;
}

.invoice-preview .payment-details {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 1rem;
}

.invoice-preview .qr-code {
    width: 100px;
    height: 100px;
    object-fit: contain;
}

.invoice-preview .terms {
    margin-top: 2rem;
    padding-top: 1rem;
    border-top: 1px solid var(--border-color);
    font-size: 0.75rem;
    color: var(--text-secondary);
}

.invoice-preview .terms h4 {
    font-size: 0.8rem;
    margin-bottom: 0.5rem;
    color: var(--text-primary);
}

/* Toast Notifications */
.toast-container {
    position: fixed;
    bottom: 1.5rem;
    right: 1.5rem;
    z-index: 2000;
    display: flex;
    flex-direction: column;
    gap: 0.75rem;
}

.toast {
    background: var(--surface);
    padding: 1rem 1.5rem;
    border-radius: var(--radius);
    box-shadow: var(--shadow-lg);
    display: flex;
    align-items: center;
    gap: 0.75rem;
    min-width: 300px;
    animation: slideIn 0.3s ease;
    border-left: 4px solid var(--primary-color);
}

.toast.success { border-left-color: var(--success-color); }
.toast.error { border-left-color: var(--danger-color); }
.toast.warning { border-left-color: var(--warning-color); }

@keyframes slideIn {
    from { transform: translateX(100%); opacity: 0; }
    to { transform: translateX(0); opacity: 1; }
}

/* Responsive Design */
@media (max-width: 1024px) {
    .dashboard-grid {
        grid-template-columns: 1fr;
    }
    
    .form-grid {
        grid-template-columns: 1fr;
    }
    
    .form-grid .full-width {
        grid-column: span 1;
    }
    
    .invoice-grid {
        grid-template-columns: 1fr;
    }
    
    .invoice-grid .full-width {
        grid-column: span 1;
    }
}

@media (max-width: 768px) {
    .sidebar {
        transform: translateX(-100%);
    }
    
    .sidebar.active {
        transform: translateX(0);
    }
    
    .main-content {
        margin-left: 0;
    }
    
    .mobile-menu-btn {
        display: block;
    }
    
    .sidebar-toggle {
        display: block;
    }
    
    .form-row {
        grid-template-columns: 1fr;
    }
    
    .stats-grid {
        grid-template-columns: 1fr;
    }
    
    .section-header {
        flex-direction: column;
        align-items: flex-start;
    }
    
    .invoice-preview .invoice-header {
        flex-direction: column;
        gap: 1rem;
    }
    
    .invoice-preview .invoice-title {
        text-align: left;
    }
    
    .invoice-preview .invoice-details {
        grid-template-columns: 1fr;
    }
    
    .invoice-preview .payment-details {
        grid-template-columns: 1fr;
    }
    
    .modal-footer {
        flex-wrap: wrap;
    }
    
    .content-area {
        padding: 1rem;
    }
}

/* Print Styles */
@media print {
    .sidebar,
    .top-header,
    .modal-header,
    .modal-footer {
        display: none !important;
    }
    
    .main-content {
        margin-left: 0;
    }
    
    .invoice-preview {
        padding: 0;
    }
}