/* Modern CSS with CSS Variables */
:root {
    --primary-color: #4361ee;
    --secondary-color: #3f37c9;
    --success-color: #4cc9f0;
    --danger-color: #f72585;
    --warning-color: #f8961e;
    --info-color: #4895ef;
    --light-color: #f8f9fa;
    --dark-color: #212529;
    --gray-color: #6c757d;
    --border-color: #dee2e6;
    --bg-color: #f5f5f5;
    --card-bg: #ffffff;
    --text-color: #333333;
    --text-muted: #6c757d;
    --font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, sans-serif;
    --border-radius: 8px;
    --box-shadow: 0 2px 4px rgba(0,0,0,0.1);
    --transition: all 0.3s ease;
}

/* Dark mode support */
@media (prefers-color-scheme: dark) {
    :root {
        --bg-color: #1a1a1a;
        --card-bg: #2d2d2d;
        --text-color: #ffffff;
        --text-muted: #a0a0a0;
        --border-color: #404040;
        --light-color: #333333;
    }
}

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

body {
    font-family: var(--font-family);
    line-height: 1.6;
    color: var(--text-color);
    background-color: var(--bg-color);
}

/* Container */
.container {
    width: 100%;
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
}

/* Typography */
h1, h2, h3, h4, h5, h6 {
    margin-bottom: 1rem;
    font-weight: 600;
    line-height: 1.2;
}

h1 { font-size: 2.5rem; }
h2 { font-size: 2rem; }
h3 { font-size: 1.75rem; }
h4 { font-size: 1.5rem; }
h5 { font-size: 1.25rem; }
h6 { font-size: 1rem; }

p {
    margin-bottom: 1rem;
}

/* Links */
a {
    color: var(--primary-color);
    text-decoration: none;
    transition: var(--transition);
}

a:hover {
    color: var(--secondary-color);
}

/* Buttons */
.btn {
    display: inline-block;
    padding: 0.5rem 1rem;
    font-size: 1rem;
    font-weight: 500;
    line-height: 1.5;
    text-align: center;
    text-decoration: none;
    vertical-align: middle;
    cursor: pointer;
    border: 1px solid transparent;
    border-radius: var(--border-radius);
    transition: var(--transition);
}

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

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

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

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

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

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

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

.btn-sm {
    padding: 0.25rem 0.5rem;
    font-size: 0.875rem;
}

.btn-lg {
    padding: 0.75rem 1.5rem;
    font-size: 1.125rem;
}

.btn-block {
    display: block;
    width: 100%;
}

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

.form-label {
    display: block;
    margin-bottom: 0.5rem;
    font-weight: 500;
}

.form-control {
    display: block;
    width: 100%;
    padding: 0.5rem 0.75rem;
    font-size: 1rem;
    line-height: 1.5;
    color: var(--text-color);
    background-color: var(--card-bg);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    transition: var(--transition);
}

.form-control:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 0.2rem rgba(67, 97, 238, 0.25);
}

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

.invalid-feedback {
    display: block;
    width: 100%;
    margin-top: 0.25rem;
    font-size: 0.875rem;
    color: var(--danger-color);
}

/* Cards */
.card {
    background-color: var(--card-bg);
    border-radius: var(--border-radius);
    box-shadow: var(--box-shadow);
    margin-bottom: 1rem;
}

.card-header {
    padding: 1rem;
    border-bottom: 1px solid var(--border-color);
    font-weight: 600;
}

.card-body {
    padding: 1rem;
}

.card-footer {
    padding: 1rem;
    border-top: 1px solid var(--border-color);
}

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

.table {
    width: 100%;
    margin-bottom: 1rem;
    background-color: var(--card-bg);
    border-collapse: collapse;
}

.table th,
.table td {
    padding: 0.75rem;
    vertical-align: top;
    border-top: 1px solid var(--border-color);
}

.table thead th {
    vertical-align: bottom;
    border-bottom: 2px solid var(--border-color);
    background-color: var(--light-color);
}

.table tbody tr:hover {
    background-color: rgba(0, 0, 0, 0.05);
}

/* Alerts */
.alert {
    position: relative;
    padding: 1rem;
    margin-bottom: 1rem;
    border: 1px solid transparent;
    border-radius: var(--border-radius);
}

.alert-success {
    color: #0f5132;
    background-color: #d1e7dd;
    border-color: #badbcc;
}

.alert-danger {
    color: #842029;
    background-color: #f8d7da;
    border-color: #f5c2c7;
}

.alert-warning {
    color: #664d03;
    background-color: #fff3cd;
    border-color: #ffecb5;
}

.alert-info {
    color: #055160;
    background-color: #cff4fc;
    border-color: #b6effb;
}

/* Navbar */
.navbar {
    background-color: var(--card-bg);
    box-shadow: var(--box-shadow);
    padding: 1rem 0;
    margin-bottom: 2rem;
}

.navbar-container {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.navbar-brand {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--primary-color);
}

.navbar-nav {
    display: flex;
    list-style: none;
    gap: 1rem;
}

.nav-link {
    color: var(--text-color);
    padding: 0.5rem;
}

.nav-link:hover,
.nav-link.active {
    color: var(--primary-color);
}

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

.stat-card {
    background-color: var(--card-bg);
    border-radius: var(--border-radius);
    padding: 1.5rem;
    box-shadow: var(--box-shadow);
    display: flex;
    align-items: center;
    gap: 1rem;
}

.stat-icon {
    width: 50px;
    height: 50px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.5rem;
}

.stat-icon.primary { background-color: rgba(67, 97, 238, 0.1); color: var(--primary-color); }
.stat-icon.success { background-color: rgba(76, 201, 240, 0.1); color: var(--success-color); }
.stat-icon.warning { background-color: rgba(248, 150, 30, 0.1); color: var(--warning-color); }
.stat-icon.danger { background-color: rgba(247, 37, 133, 0.1); color: var(--danger-color); }

.stat-content h3 {
    font-size: 0.875rem;
    color: var(--text-muted);
    margin-bottom: 0.25rem;
}

.stat-value {
    font-size: 1.5rem;
    font-weight: 700;
}

/* Modal */
.modal {
    display: none;
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-color: rgba(0, 0, 0, 0.5);
    z-index: 1000;
}

.modal.show {
    display: flex;
    align-items: center;
    justify-content: center;
}

.modal-dialog {
    width: 100%;
    max-width: 500px;
    margin: 1rem;
}

.modal-content {
    background-color: var(--card-bg);
    border-radius: var(--border-radius);
    box-shadow: var(--box-shadow);
}

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

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

.modal-close {
    background: none;
    border: none;
    font-size: 1.5rem;
    cursor: pointer;
    color: var(--text-muted);
}

.modal-body {
    padding: 1rem;
}

.modal-footer {
    padding: 1rem;
    border-top: 1px solid var(--border-color);
    display: flex;
    justify-content: flex-end;
    gap: 0.5rem;
}

/* Invoice Builder */
.invoice-builder {
    background-color: var(--card-bg);
    border-radius: var(--border-radius);
    padding: 2rem;
    box-shadow: var(--box-shadow);
}

.items-table {
    margin: 1rem 0;
}

.items-table th {
    background-color: var(--light-color);
    padding: 0.75rem;
}

.items-table td {
    padding: 0.75rem;
}

.item-row {
    transition: var(--transition);
}

.item-row:hover {
    background-color: rgba(0, 0, 0, 0.05);
}

.remove-item {
    color: var(--danger-color);
    cursor: pointer;
}

.totals-section {
    margin-top: 2rem;
    padding-top: 1rem;
    border-top: 2px solid var(--border-color);
}

.total-row {
    display: flex;
    justify-content: flex-end;
    margin-bottom: 0.5rem;
}

.total-label {
    width: 200px;
    font-weight: 600;
}

.total-value {
    width: 200px;
    text-align: right;
}

.grand-total {
    font-size: 1.25rem;
    font-weight: 700;
    color: var(--primary-color);
}

/* Invoice Preview */
.invoice-preview {
    background-color: var(--card-bg);
    border-radius: var(--border-radius);
    padding: 2rem;
    box-shadow: var(--box-shadow);
}

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

.invoice-title {
    font-size: 2rem;
    font-weight: 700;
    color: var(--primary-color);
}

.invoice-number {
    font-size: 1.25rem;
    color: var(--text-muted);
}

.invoice-info {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 2rem;
    margin-bottom: 2rem;
}

.info-group h4 {
    color: var(--text-muted);
    font-size: 0.875rem;
    margin-bottom: 0.5rem;
}

.info-group p {
    margin-bottom: 0.25rem;
}

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

.mt-1 { margin-top: 0.5rem; }
.mt-2 { margin-top: 1rem; }
.mt-3 { margin-top: 1.5rem; }
.mt-4 { margin-top: 2rem; }
.mt-5 { margin-top: 3rem; }

.mb-1 { margin-bottom: 0.5rem; }
.mb-2 { margin-bottom: 1rem; }
.mb-3 { margin-bottom: 1.5rem; }
.mb-4 { margin-bottom: 2rem; }
.mb-5 { margin-bottom: 3rem; }

.p-1 { padding: 0.5rem; }
.p-2 { padding: 1rem; }
.p-3 { padding: 1.5rem; }
.p-4 { padding: 2rem; }
.p-5 { padding: 3rem; }

.d-flex { display: flex; }
.flex-column { flex-direction: column; }
.justify-between { justify-content: space-between; }
.align-center { align-items: center; }
.gap-1 { gap: 0.5rem; }
.gap-2 { gap: 1rem; }
.gap-3 { gap: 1.5rem; }

.w-100 { width: 100%; }

/* Responsive */
@media (max-width: 768px) {
    .navbar-nav {
        flex-direction: column;
        position: absolute;
        top: 100%;
        left: 0;
        right: 0;
        background-color: var(--card-bg);
        padding: 1rem;
        box-shadow: var(--box-shadow);
        display: none;
    }
    
    .navbar-nav.show {
        display: flex;
    }
    
    .navbar-toggler {
        display: block;
        background: none;
        border: none;
        font-size: 1.5rem;
        cursor: pointer;
    }
    
    .dashboard-stats {
        grid-template-columns: 1fr;
    }
    
    .invoice-header {
        flex-direction: column;
        text-align: center;
        gap: 1rem;
    }
    
    .invoice-info {
        grid-template-columns: 1fr;
        gap: 1rem;
    }
    
    .table-responsive table {
        font-size: 0.875rem;
    }
    
    .table-responsive th,
    .table-responsive td {
        padding: 0.5rem;
    }
    
    .btn {
        padding: 0.4rem 0.8rem;
        font-size: 0.875rem;
    }
}

/* Loading Spinner */
.spinner {
    border: 3px solid rgba(0, 0, 0, 0.1);
    border-radius: 50%;
    border-top: 3px solid var(--primary-color);
    width: 40px;
    height: 40px;
    animation: spin 1s linear infinite;
}

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

/* Print Styles */
@media print {
    .no-print {
        display: none !important;
    }
    
    body {
        background-color: white;
    }
    
    .invoice-preview {
        box-shadow: none;
        padding: 0;
    }
}