/* CSS Variables for theming */
:root {
    --primary-color: #4f46e5;
    --primary-hover: #4338ca;
    --secondary-color: #6b7280;
    --success-color: #10b981;
    --warning-color: #f59e0b;
    --danger-color: #ef4444;
    --info-color: #3b82f6;

    --bg-primary: #f9fafb;
    --bg-secondary: #ffffff;
    --bg-tertiary: #f3f4f6;

    --text-primary: #111827;
    --text-secondary: #6b7280;
    --text-muted: #9ca3af;

    --border-color: #e5e7eb;
    --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.05);
    --shadow: 0 1px 3px 0 rgb(0 0 0 / 0.1), 0 1px 2px -1px rgb(0 0 0 / 0.1);
    --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.1), 0 2px 4px -2px rgb(0 0 0 / 0.1);
    --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.1), 0 4px 6px -4px rgb(0 0 0 / 0.1);

    --radius-sm: 0.375rem;
    --radius: 0.5rem;
    --radius-lg: 0.75rem;
    --radius-xl: 1rem;

    --transition: all 0.2s ease;
}

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

html {
    font-size: 16px;
    scroll-behavior: smooth;
}

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

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

/* Header */
.header {
    background: linear-gradient(135deg, var(--primary-color) 0%, #7c3aed 100%);
    color: white;
    padding: 1.5rem;
    text-align: center;
}

.header-content {
    max-width: 1200px;
    margin: 0 auto;
}

.logo {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0.75rem;
    margin-bottom: 0.5rem;
}

.logo-img {
    width: 40px;
    height: 40px;
    object-fit: contain;
}

.logo h1 {
    font-size: 1.75rem;
    font-weight: 700;
    margin: 0;
}

.tagline {
    font-size: 1rem;
    opacity: 0.9;
    margin: 0;
}

/* Navigation Tabs */
.nav-tabs {
    display: flex;
    background-color: var(--bg-secondary);
    border-bottom: 1px solid var(--border-color);
    overflow-x: auto;
    -webkit-overflow-scrolling: touch;
}

.tab-btn {
    flex: 1;
    min-width: max-content;
    padding: 1rem 1.5rem;
    border: none;
    background: none;
    cursor: pointer;
    font-size: 0.875rem;
    font-weight: 500;
    color: var(--text-secondary);
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0.5rem;
    transition: var(--transition);
    border-bottom: 2px solid transparent;
}

.tab-btn:hover {
    color: var(--primary-color);
    background-color: var(--bg-tertiary);
}

.tab-btn.active {
    color: var(--primary-color);
    border-bottom-color: var(--primary-color);
    background-color: var(--bg-secondary);
}

.tab-icon {
    font-size: 1.125rem;
}

/* Main Content */
.main-content {
    flex: 1;
    max-width: 1200px;
    width: 100%;
    margin: 0 auto;
    padding: 1.5rem;
}

.tab-content {
    display: none;
}

.tab-content.active {
    display: block;
    animation: fadeIn 0.3s ease;
}

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

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

.section-header h2 {
    font-size: 1.5rem;
    font-weight: 600;
    color: var(--text-primary);
}

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

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

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

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

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

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

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

.btn-sm {
    padding: 0.375rem 0.75rem;
    font-size: 0.75rem;
}

.btn-icon {
    padding: 0.5rem;
    min-width: auto;
}

/* Form Card */
.form-card {
    background-color: var(--bg-secondary);
    border-radius: var(--radius-lg);
    padding: 1.5rem;
    margin-bottom: 1.5rem;
    box-shadow: var(--shadow);
    border: 1px solid var(--border-color);
}

.form-card h3 {
    font-size: 1.125rem;
    font-weight: 600;
    margin-bottom: 1.25rem;
    color: var(--text-primary);
}

/* Form Elements */
.form-row {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 1rem;
}

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

.form-group label {
    display: block;
    font-size: 0.875rem;
    font-weight: 500;
    color: var(--text-secondary);
    margin-bottom: 0.375rem;
}

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

.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 rgba(79, 70, 229, 0.1);
}

.form-group input::placeholder,
.form-group textarea::placeholder {
    color: var(--text-muted);
}

.form-group input[type="checkbox"] {
    width: auto;
    margin-right: 0.5rem;
}

.form-group label:has(input[type="checkbox"]) {
    display: flex;
    align-items: center;
    cursor: pointer;
}

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

/* List Container */
.list-container {
    background-color: var(--bg-secondary);
    border-radius: var(--radius-lg);
    padding: 1.5rem;
    box-shadow: var(--shadow);
    border: 1px solid var(--border-color);
    margin-bottom: 1.5rem;
}

.list-container h3 {
    font-size: 1rem;
    font-weight: 600;
    margin-bottom: 1rem;
    color: var(--text-primary);
}

/* Search and Filter */
.search-filter {
    display: flex;
    gap: 0.75rem;
    margin-bottom: 1rem;
    flex-wrap: wrap;
}

.search-filter input {
    flex: 1;
    min-width: 200px;
    padding: 0.625rem 0.875rem;
    font-size: 0.875rem;
    border: 1px solid var(--border-color);
    border-radius: var(--radius);
    background-color: var(--bg-secondary);
}

.search-filter select {
    padding: 0.625rem 0.875rem;
    font-size: 0.875rem;
    border: 1px solid var(--border-color);
    border-radius: var(--radius);
    background-color: var(--bg-secondary);
    min-width: 150px;
}

/* Table */
.table-responsive {
    overflow-x: auto;
    -webkit-overflow-scrolling: touch;
}

.data-table {
    width: 100%;
    border-collapse: collapse;
    font-size: 0.875rem;
}

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

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

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

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

/* Status Badges */
.status-badge {
    display: inline-block;
    padding: 0.25rem 0.625rem;
    font-size: 0.75rem;
    font-weight: 500;
    border-radius: 9999px;
    text-transform: capitalize;
}

.status-badge.pending {
    background-color: #fef3c7;
    color: #92400e;
}

.status-badge.partial {
    background-color: #dbeafe;
    color: #1e40af;
}

.status-badge.paid {
    background-color: #d1fae5;
    color: #065f46;
}

.status-badge.overdue {
    background-color: #fee2e2;
    color: #991b1b;
}

/* Action Buttons */
.action-buttons {
    display: flex;
    gap: 0.375rem;
}

.action-btn {
    padding: 0.375rem 0.5rem;
    font-size: 0.75rem;
    border: none;
    border-radius: var(--radius-sm);
    cursor: pointer;
    transition: var(--transition);
    background-color: var(--bg-tertiary);
    color: var(--text-secondary);
}

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

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

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

.action-btn.send {
    color: var(--success-color);
}

/* Empty State */
.empty-state {
    text-align: center;
    padding: 3rem 1.5rem;
    color: var(--text-secondary);
}

.empty-icon {
    font-size: 3rem;
    display: block;
    margin-bottom: 1rem;
}

.empty-state p {
    font-size: 0.875rem;
}

/* Summary Cards */
.summary-cards {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 1rem;
    margin-bottom: 1.5rem;
}

.summary-card {
    background-color: var(--bg-secondary);
    border-radius: var(--radius-lg);
    padding: 1.25rem;
    box-shadow: var(--shadow);
    border: 1px solid var(--border-color);
    display: flex;
    align-items: center;
    gap: 1rem;
}

.summary-icon {
    font-size: 2rem;
    width: 50px;
    height: 50px;
    display: flex;
    align-items: center;
    justify-content: center;
    background-color: var(--bg-tertiary);
    border-radius: var(--radius);
}

.summary-content {
    display: flex;
    flex-direction: column;
}

.summary-label {
    font-size: 0.75rem;
    color: var(--text-secondary);
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.summary-value {
    font-size: 1.25rem;
    font-weight: 700;
    color: var(--text-primary);
}

/* Report Section */
.report-section {
    background-color: var(--bg-secondary);
    border-radius: var(--radius-lg);
    padding: 1.5rem;
    box-shadow: var(--shadow);
    border: 1px solid var(--border-color);
    margin-bottom: 1.5rem;
}

.report-section h3 {
    font-size: 1rem;
    font-weight: 600;
    margin-bottom: 1rem;
    color: var(--text-primary);
}

.report-filter {
    background-color: var(--bg-secondary);
    border-radius: var(--radius-lg);
    padding: 1.25rem;
    box-shadow: var(--shadow);
    border: 1px solid var(--border-color);
    margin-bottom: 1.5rem;
}

.report-filter .form-row {
    align-items: flex-end;
}

.report-filter .form-group {
    margin-bottom: 0;
}

.report-actions {
    display: flex;
    gap: 0.75rem;
}

/* Status Bar */
.status-bar {
    height: 24px;
    background-color: var(--bg-tertiary);
    border-radius: var(--radius);
    overflow: hidden;
    display: flex;
}

.status-segment {
    height: 100%;
    transition: width 0.5s ease;
}

.status-segment.paid {
    background-color: var(--success-color);
}

.status-segment.partial {
    background-color: var(--info-color);
}

.status-segment.pending {
    background-color: var(--warning-color);
}

.status-segment.overdue {
    background-color: var(--danger-color);
}

.status-legend {
    display: flex;
    flex-wrap: wrap;
    gap: 1rem;
    margin-top: 0.75rem;
    font-size: 0.875rem;
}

.legend-item {
    display: flex;
    align-items: center;
    gap: 0.375rem;
}

.legend-color {
    width: 12px;
    height: 12px;
    border-radius: 2px;
}

.legend-color.paid {
    background-color: var(--success-color);
}

.legend-color.partial {
    background-color: var(--info-color);
}

.legend-color.pending {
    background-color: var(--warning-color);
}

.legend-color.overdue {
    background-color: var(--danger-color);
}

/* Footer */
.footer {
    background-color: var(--bg-secondary);
    border-top: 1px solid var(--border-color);
    padding: 1.5rem;
    text-align: center;
}

.footer p {
    font-size: 0.875rem;
    color: var(--text-secondary);
    margin: 0;
}

.footer a {
    color: var(--primary-color);
    text-decoration: none;
    font-weight: 500;
}

.footer a:hover {
    text-decoration: underline;
}

/* Toast Notifications */
.toast-container {
    position: fixed;
    bottom: 1.5rem;
    right: 1.5rem;
    z-index: 1000;
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

.toast {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    padding: 1rem 1.25rem;
    background-color: var(--bg-secondary);
    border-radius: var(--radius);
    box-shadow: var(--shadow-lg);
    border: 1px solid var(--border-color);
    animation: slideIn 0.3s ease;
    max-width: 350px;
}

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

.toast.success {
    border-left: 4px solid var(--success-color);
}

.toast.error {
    border-left: 4px solid var(--danger-color);
}

.toast.warning {
    border-left: 4px solid var(--warning-color);
}

.toast.info {
    border-left: 4px solid var(--info-color);
}

.toast-icon {
    font-size: 1.25rem;
}

.toast-message {
    flex: 1;
    font-size: 0.875rem;
}

.toast-close {
    background: none;
    border: none;
    color: var(--text-muted);
    cursor: pointer;
    padding: 0.25rem;
    font-size: 1rem;
}

/* Modal */
.modal-overlay {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background-color: rgba(0, 0, 0, 0.5);
    display: flex;
    align-items: center;
    justify-content: center;
    z-index: 1001;
    opacity: 0;
    visibility: hidden;
    transition: var(--transition);
    padding: 1rem;
}

.modal-overlay.active {
    opacity: 1;
    visibility: visible;
}

.modal {
    background-color: var(--bg-secondary);
    border-radius: var(--radius-lg);
    padding: 1.5rem;
    max-width: 400px;
    width: 100%;
    box-shadow: var(--shadow-lg);
    transform: scale(0.9);
    transition: var(--transition);
}

.modal-overlay.active .modal {
    transform: scale(1);
}

.modal-large {
    max-width: 600px;
}

.modal h3 {
    font-size: 1.125rem;
    font-weight: 600;
    margin-bottom: 0.75rem;
}

.modal p {
    color: var(--text-secondary);
    margin-bottom: 1.5rem;
}

.modal-actions {
    display: flex;
    justify-content: flex-end;
    gap: 0.75rem;
}

/* Email Preview */
.email-preview {
    background-color: var(--bg-tertiary);
    border-radius: var(--radius);
    padding: 1rem;
    margin-bottom: 1rem;
    font-family: monospace;
    font-size: 0.8125rem;
    line-height: 1.6;
    max-height: 300px;
    overflow-y: auto;
}

.email-preview strong {
    display: block;
    margin-bottom: 0.5rem;
    color: var(--text-primary);
}

/* Mobile Responsive */
@media (max-width: 768px) {
    .header {
        padding: 1rem;
    }

    .logo h1 {
        font-size: 1.25rem;
    }

    .tagline {
        font-size: 0.875rem;
    }

    .nav-tabs {
        justify-content: flex-start;
    }

    .tab-btn {
        padding: 0.875rem 1rem;
        flex: 0 0 auto;
    }

    .tab-text {
        display: none;
    }

    .tab-icon {
        font-size: 1.25rem;
    }

    .main-content {
        padding: 1rem;
    }

    .section-header {
        flex-direction: column;
        align-items: stretch;
    }

    .section-header h2 {
        margin-bottom: 0.5rem;
    }

    .form-row {
        grid-template-columns: 1fr;
    }

    .form-actions {
        flex-direction: column;
    }

    .form-actions .btn {
        width: 100%;
        justify-content: center;
    }

    .search-filter {
        flex-direction: column;
    }

    .search-filter input,
    .search-filter select {
        width: 100%;
    }

    .data-table th,
    .data-table td {
        padding: 0.625rem 0.5rem;
        font-size: 0.8125rem;
    }

    .summary-cards {
        grid-template-columns: 1fr 1fr;
    }

    .summary-card {
        padding: 1rem;
    }

    .summary-icon {
        width: 40px;
        height: 40px;
        font-size: 1.5rem;
    }

    .summary-value {
        font-size: 1rem;
    }

    .status-legend {
        flex-direction: column;
        gap: 0.5rem;
    }

    .toast-container {
        left: 1rem;
        right: 1rem;
        bottom: 1rem;
    }

    .toast {
        max-width: 100%;
    }

    .report-actions {
        width: 100%;
    }

    .report-actions .btn {
        flex: 1;
        justify-content: center;
    }
}

@media (max-width: 480px) {
    .summary-cards {
        grid-template-columns: 1fr;
    }

    .action-buttons {
        flex-direction: column;
    }

    .modal {
        padding: 1rem;
    }
}

/* Print Styles */
@media print {
    .header,
    .nav-tabs,
    .form-card,
    .search-filter,
    .action-buttons,
    .modal-overlay,
    .toast-container,
    .btn {
        display: none !important;
    }

    .main-content {
        padding: 0;
    }

    .tab-content {
        display: block !important;
    }

    .list-container,
    .summary-card,
    .report-section {
        box-shadow: none;
        border: 1px solid #ddd;
    }
}