/* Modern Billing ERP CSS */
:root {
    --primary-color: #2563eb;
    --primary-dark: #1d4ed8;
    --secondary-color: #64748b;
    --success-color: #10b981;
    --warning-color: #f59e0b;
    --danger-color: #ef4444;
    --info-color: #06b6d4;
    --light-color: #f8fafc;
    --dark-color: #1e293b;
    --sidebar-width: 280px;
    --sidebar-collapsed-width: 80px;
    --border-radius: 12px;
    --border-radius-sm: 8px;
    --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);
    --transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

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

body {
    font-family: 'Inter', 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background-color: #f1f5f9;
    color: var(--dark-color);
    line-height: 1.6;
    overflow-x: hidden;
}

/* Typography */
h1, h2, h3, h4, h5, h6 {
    font-weight: 600;
    margin-bottom: 0.5rem;
}

h1 { font-size: 2.25rem; }
h2 { font-size: 1.875rem; }
h3 { font-size: 1.5rem; }
h4 { font-size: 1.25rem; }
h5 { font-size: 1.125rem; }
h6 { font-size: 1rem; }

/* Sidebar */
.sidebar {
    position: fixed;
    top: 0;
    left: 0;
    height: 100vh;
    width: var(--sidebar-width);
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    box-shadow: var(--shadow-lg);
    z-index: 1000;
    transform: translateX(0);
    transition: var(--transition);
    overflow: hidden;
}

.sidebar.collapsed {
    width: var(--sidebar-collapsed-width);
}

.sidebar-header {
    padding: 1.5rem;
    border-bottom: 1px solid rgba(255, 255, 255, 0.1);
    display: flex;
    align-items: center;
    justify-content: space-between;
}

.sidebar-brand {
    display: flex;
    align-items: center;
    color: white;
    text-decoration: none;
    font-weight: 700;
    font-size: 1.25rem;
    white-space: nowrap;
    opacity: 1;
    transition: var(--transition);
}

.sidebar.collapsed .sidebar-brand-text {
    opacity: 0;
    width: 0;
    overflow: hidden;
}

.sidebar-brand-icon {
    font-size: 1.5rem;
    margin-right: 0.75rem;
    min-width: 24px;
}

.sidebar-toggle {
    background: none;
    border: none;
    color: white;
    font-size: 1.25rem;
    cursor: pointer;
    padding: 0.5rem;
    border-radius: var(--border-radius-sm);
    transition: var(--transition);
}

.sidebar-toggle:hover {
    background: rgba(255, 255, 255, 0.1);
}

.sidebar-nav {
    padding: 1rem 0;
    height: calc(100vh - 100px);
    overflow-y: auto;
}

.sidebar-nav::-webkit-scrollbar {
    width: 6px;
}

.sidebar-nav::-webkit-scrollbar-track {
    background: rgba(255, 255, 255, 0.1);
}

.sidebar-nav::-webkit-scrollbar-thumb {
    background: rgba(255, 255, 255, 0.3);
    border-radius: 3px;
}

.nav-item {
    margin: 0.25rem 1rem;
}

.nav-link {
    display: flex;
    align-items: center;
    padding: 0.75rem 1rem;
    color: rgba(255, 255, 255, 0.8);
    text-decoration: none;
    border-radius: var(--border-radius);
    transition: var(--transition);
    position: relative;
    white-space: nowrap;
}

.nav-link:hover {
    background: rgba(255, 255, 255, 0.1);
    color: white;
    transform: translateX(4px);
}

.nav-link.active {
    background: rgba(255, 255, 255, 0.15);
    color: white;
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.15);
}

.nav-link-icon {
    font-size: 1.25rem;
    margin-right: 0.75rem;
    min-width: 20px;
    text-align: center;
}

.nav-link-text {
    opacity: 1;
    transition: var(--transition);
}

.sidebar.collapsed .nav-link-text {
    opacity: 0;
    width: 0;
    overflow: hidden;
}

.sidebar.collapsed .nav-link {
    justify-content: center;
    padding: 0.75rem;
}

/* Dropdown menu */
.nav-dropdown {
    position: relative;
}

.nav-dropdown-menu {
    display: none;
    background: rgba(255, 255, 255, 0.1);
    margin: 0.5rem 0;
    border-radius: var(--border-radius-sm);
    overflow: hidden;
}

.nav-dropdown.open .nav-dropdown-menu {
    display: block;
}

.nav-dropdown-item {
    padding: 0.5rem 1rem 0.5rem 3rem;
    color: rgba(255, 255, 255, 0.7);
    text-decoration: none;
    display: block;
    transition: var(--transition);
    font-size: 0.9rem;
}

.nav-dropdown-item:hover {
    background: rgba(255, 255, 255, 0.1);
    color: white;
}

/* Main Content */
.main-content {
    margin-left: var(--sidebar-width);
    min-height: 100vh;
    transition: var(--transition);
    background-color: #f1f5f9;
}

.main-content.sidebar-collapsed {
    margin-left: var(--sidebar-collapsed-width);
}

/* Header */
.header {
    background: white;
    padding: 1rem 2rem;
    border-bottom: 1px solid #e2e8f0;
    box-shadow: var(--shadow);
    position: sticky;
    top: 0;
    z-index: 100;
}

.header-content {
    display: flex;
    justify-content: between;
    align-items: center;
}

.header-title {
    font-size: 1.5rem;
    font-weight: 600;
    color: var(--dark-color);
    margin: 0;
}

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

.user-menu {
    position: relative;
    display: inline-block;
}

.user-menu-button {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    background: none;
    border: none;
    padding: 0.5rem;
    border-radius: var(--border-radius);
    cursor: pointer;
    transition: var(--transition);
}

.user-menu-button:hover {
    background: var(--light-color);
}

.user-avatar {
    width: 40px;
    height: 40px;
    border-radius: 50%;
    background: var(--primary-color);
    display: flex;
    align-items: center;
    justify-content: center;
    color: white;
    font-weight: 600;
}

.user-menu-dropdown {
    position: absolute;
    top: 100%;
    right: 0;
    background: white;
    border-radius: var(--border-radius);
    box-shadow: var(--shadow-lg);
    min-width: 200px;
    z-index: 1000;
    border: 1px solid #e2e8f0;
    display: none;
}

.user-menu-dropdown.show {
    display: block;
}

.user-menu-item {
    padding: 0.75rem 1rem;
    border-bottom: 1px solid #f1f5f9;
    cursor: pointer;
    transition: var(--transition);
}

.user-menu-item:hover {
    background: var(--light-color);
}

.user-menu-item:last-child {
    border-bottom: none;
}

/* Content Area */
.content {
    padding: 2rem;
}

/* Cards */
.card {
    background: white;
    border-radius: var(--border-radius);
    box-shadow: var(--shadow);
    border: 1px solid #e2e8f0;
    overflow: hidden;
    margin-bottom: 1.5rem;
}

.card-header {
    padding: 1.5rem;
    border-bottom: 1px solid #e2e8f0;
    background: #f8fafc;
}

.card-title {
    font-size: 1.25rem;
    font-weight: 600;
    margin: 0;
    color: var(--dark-color);
}

.card-body {
    padding: 1.5rem;
}

.card-footer {
    padding: 1rem 1.5rem;
    border-top: 1px solid #e2e8f0;
    background: #f8fafc;
}

/* Stats Cards */
.stats-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 1.5rem;
    margin-bottom: 2rem;
}

.stat-card {
    background: white;
    padding: 1.5rem;
    border-radius: var(--border-radius);
    box-shadow: var(--shadow);
    border: 1px solid #e2e8f0;
    position: relative;
    overflow: hidden;
}

.stat-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 4px;
    background: var(--primary-color);
}

.stat-card.success::before { background: var(--success-color); }
.stat-card.warning::before { background: var(--warning-color); }
.stat-card.danger::before { background: var(--danger-color); }
.stat-card.info::before { background: var(--info-color); }

.stat-header {
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
    margin-bottom: 1rem;
}

.stat-title {
    font-size: 0.875rem;
    font-weight: 500;
    color: var(--secondary-color);
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.stat-icon {
    width: 48px;
    height: 48px;
    border-radius: var(--border-radius);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.5rem;
    color: white;
    background: var(--primary-color);
}

.stat-card.success .stat-icon { background: var(--success-color); }
.stat-card.warning .stat-icon { background: var(--warning-color); }
.stat-card.danger .stat-icon { background: var(--danger-color); }
.stat-card.info .stat-icon { background: var(--info-color); }

.stat-value {
    font-size: 2rem;
    font-weight: 700;
    color: var(--dark-color);
    margin-bottom: 0.5rem;
}

.stat-change {
    font-size: 0.875rem;
    display: flex;
    align-items: center;
    gap: 0.25rem;
}

.stat-change.positive {
    color: var(--success-color);
}

.stat-change.negative {
    color: var(--danger-color);
}

/* Buttons */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 0.5rem;
    padding: 0.75rem 1.5rem;
    font-size: 0.9rem;
    font-weight: 500;
    text-decoration: none;
    border: 1px solid transparent;
    border-radius: var(--border-radius);
    cursor: pointer;
    transition: var(--transition);
    line-height: 1;
    white-space: nowrap;
}

.btn:hover {
    transform: translateY(-1px);
    box-shadow: var(--shadow);
}

.btn:active {
    transform: translateY(0);
}

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

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

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

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

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

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

.btn-outline-primary {
    background: transparent;
    color: var(--primary-color);
    border-color: var(--primary-color);
}

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

.btn-sm {
    padding: 0.5rem 1rem;
    font-size: 0.875rem;
}

.btn-lg {
    padding: 1rem 2rem;
    font-size: 1.1rem;
}

/* Forms */
.form-group {
    margin-bottom: 1.5rem;
}

.form-label {
    display: block;
    margin-bottom: 0.5rem;
    font-weight: 500;
    color: var(--dark-color);
}

.form-control {
    width: 100%;
    padding: 0.75rem;
    font-size: 1rem;
    border: 1px solid #d1d5db;
    border-radius: var(--border-radius);
    transition: var(--transition);
    background: white;
}

.form-control:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.1);
}

.form-control:invalid {
    border-color: var(--danger-color);
}

.form-select {
    background-image: url("data:image/svg+xml,%3csvg xmlns='http://www.w3.org/2000/svg' fill='none' viewBox='0 0 20 20'%3e%3cpath stroke='%236b7280' stroke-linecap='round' stroke-linejoin='round' stroke-width='1.5' d='m6 8 4 4 4-4'/%3e%3c/svg%3e");
    background-position: right 0.75rem center;
    background-repeat: no-repeat;
    background-size: 1.5em 1.5em;
    padding-right: 2.5rem;
}

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

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

/* Tables */
.table-container {
    background: white;
    border-radius: var(--border-radius);
    box-shadow: var(--shadow);
    overflow: hidden;
    border: 1px solid #e2e8f0;
}

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

.table th,
.table td {
    padding: 1rem;
    text-align: left;
    border-bottom: 1px solid #e2e8f0;
}

.table th {
    background: #f8fafc;
    font-weight: 600;
    color: var(--dark-color);
    font-size: 0.875rem;
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.table tbody tr:hover {
    background: #f8fafc;
}

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

/* Badges */
.badge {
    display: inline-flex;
    align-items: center;
    padding: 0.25rem 0.75rem;
    font-size: 0.75rem;
    font-weight: 600;
    border-radius: 9999px;
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.badge-primary { background: rgba(37, 99, 235, 0.1); color: var(--primary-color); }
.badge-success { background: rgba(16, 185, 129, 0.1); color: var(--success-color); }
.badge-warning { background: rgba(245, 158, 11, 0.1); color: var(--warning-color); }
.badge-danger { background: rgba(239, 68, 68, 0.1); color: var(--danger-color); }
.badge-secondary { background: rgba(100, 116, 139, 0.1); color: var(--secondary-color); }

/* Alerts */
.alert {
    padding: 1rem;
    border-radius: var(--border-radius);
    margin-bottom: 1rem;
    border: 1px solid transparent;
    display: flex;
    align-items: flex-start;
    gap: 0.75rem;
}

.alert-success {
    background: rgba(16, 185, 129, 0.1);
    border-color: rgba(16, 185, 129, 0.2);
    color: #065f46;
}

.alert-danger {
    background: rgba(239, 68, 68, 0.1);
    border-color: rgba(239, 68, 68, 0.2);
    color: #991b1b;
}

.alert-warning {
    background: rgba(245, 158, 11, 0.1);
    border-color: rgba(245, 158, 11, 0.2);
    color: #92400e;
}

.alert-info {
    background: rgba(6, 182, 212, 0.1);
    border-color: rgba(6, 182, 212, 0.2);
    color: #155e75;
}

.alert-dismissible {
    position: relative;
    padding-right: 3rem;
}

.btn-close {
    position: absolute;
    top: 0.5rem;
    right: 0.5rem;
    background: none;
    border: none;
    font-size: 1.25rem;
    cursor: pointer;
    padding: 0.5rem;
    line-height: 1;
    color: inherit;
    opacity: 0.5;
}

.btn-close:hover {
    opacity: 1;
}

/* Pagination */
.pagination {
    display: flex;
    justify-content: center;
    gap: 0.25rem;
    margin: 2rem 0;
}

.page-item {
    list-style: none;
}

.page-link {
    display: block;
    padding: 0.75rem 1rem;
    text-decoration: none;
    color: var(--primary-color);
    border: 1px solid #d1d5db;
    border-radius: var(--border-radius);
    transition: var(--transition);
}

.page-link:hover {
    background: var(--primary-color);
    color: white;
    border-color: var(--primary-color);
}

.page-item.active .page-link {
    background: var(--primary-color);
    color: white;
    border-color: var(--primary-color);
}

.page-item.disabled .page-link {
    color: var(--secondary-color);
    cursor: not-allowed;
    opacity: 0.5;
}

/* Modal */
.modal {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(0, 0, 0, 0.5);
    z-index: 1050;
    display: none;
    align-items: center;
    justify-content: center;
    backdrop-filter: blur(4px);
}

.modal.show {
    display: flex;
}

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

.modal-header {
    padding: 1.5rem;
    border-bottom: 1px solid #e2e8f0;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.modal-title {
    font-size: 1.25rem;
    font-weight: 600;
    margin: 0;
}

.modal-body {
    padding: 1.5rem;
}

.modal-footer {
    padding: 1rem 1.5rem;
    border-top: 1px solid #e2e8f0;
    display: flex;
    justify-content: flex-end;
    gap: 1rem;
}

/* Loading Spinner */
.spinner {
    width: 20px;
    height: 20px;
    border: 2px solid #f3f3f3;
    border-top: 2px solid var(--primary-color);
    border-radius: 50%;
    animation: spin 1s linear infinite;
}

@keyframes spin {
    0% { transform: rotate(0deg); }
    100% { transform: rotate(360deg); }
}

/* Responsive Design */
@media (max-width: 768px) {
    .sidebar {
        width: var(--sidebar-collapsed-width);
    }
    
    .sidebar:not(.collapsed) {
        width: var(--sidebar-width);
    }
    
    .main-content {
        margin-left: var(--sidebar-collapsed-width);
    }
    
    .main-content.sidebar-expanded {
        margin-left: var(--sidebar-width);
    }
    
    .content {
        padding: 1rem;
    }
    
    .form-row {
        grid-template-columns: 1fr;
    }
    
    .stats-grid {
        grid-template-columns: 1fr;
    }
    
    .header-title {
        font-size: 1.25rem;
    }
    
    .table-container {
        overflow-x: auto;
    }
    
    .table {
        min-width: 600px;
    }
}

/* Print Styles */
@media print {
    .sidebar,
    .header,
    .btn,
    .pagination {
        display: none !important;
    }
    
    .main-content {
        margin-left: 0 !important;
    }
    
    .card {
        box-shadow: none;
        border: 1px solid #ddd;
    }
}

/* Utilities */
.text-center { text-align: center; }
.text-right { text-align: right; }
.text-left { text-align: left; }

.text-primary { color: var(--primary-color); }
.text-success { color: var(--success-color); }
.text-warning { color: var(--warning-color); }
.text-danger { color: var(--danger-color); }
.text-secondary { color: var(--secondary-color); }

.bg-primary { background-color: var(--primary-color); }
.bg-success { background-color: var(--success-color); }
.bg-warning { background-color: var(--warning-color); }
.bg-danger { background-color: var(--danger-color); }
.bg-light { background-color: var(--light-color); }

.d-none { display: none; }
.d-block { display: block; }
.d-flex { display: flex; }
.d-grid { display: grid; }

.justify-content-center { justify-content: center; }
.justify-content-between { justify-content: space-between; }
.justify-content-end { justify-content: flex-end; }

.align-items-center { align-items: center; }
.align-items-start { align-items: flex-start; }
.align-items-end { align-items: flex-end; }

.gap-1 { gap: 0.25rem; }
.gap-2 { gap: 0.5rem; }
.gap-3 { gap: 0.75rem; }
.gap-4 { gap: 1rem; }

.m-0 { margin: 0; }
.m-1 { margin: 0.25rem; }
.m-2 { margin: 0.5rem; }
.m-3 { margin: 0.75rem; }
.m-4 { margin: 1rem; }

.mb-0 { margin-bottom: 0; }
.mb-1 { margin-bottom: 0.25rem; }
.mb-2 { margin-bottom: 0.5rem; }
.mb-3 { margin-bottom: 0.75rem; }
.mb-4 { margin-bottom: 1rem; }

.p-0 { padding: 0; }
.p-1 { padding: 0.25rem; }
.p-2 { padding: 0.5rem; }
.p-3 { padding: 0.75rem; }
.p-4 { padding: 1rem; }

.w-100 { width: 100%; }
.h-100 { height: 100%; }

.rounded { border-radius: var(--border-radius); }
.rounded-sm { border-radius: var(--border-radius-sm); }
.rounded-full { border-radius: 9999px; }

.shadow { box-shadow: var(--shadow); }
.shadow-lg { box-shadow: var(--shadow-lg); }

/* Font Awesome Icons */
.fas, .far, .fab {
    font-family: "Font Awesome 5 Free", "Font Awesome 5 Brands";
    font-weight: 900;
}