:root {
    --primary: #4f46e5;
    --primary-hover: #4338ca;
    --secondary: #0ea5e9;
    --accent: #f59e0b;
    --success: #10b981;
    --danger: #ef4444;
    --background: #f8fafc;
    --glass: rgba(255, 255, 255, 0.7);
    --card-bg: #ffffff;
    --text-main: #1e293b;
    --text-muted: #64748b;
    --border: #e2e8f0;
    --shadow: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: 'Inter', system-ui, -apple-system, sans-serif;
}

body {
    background-color: var(--background);
    color: var(--text-main);
    min-height: 100vh;
    overflow-x: hidden;
}

/* Background Decoration */
body::before {
    content: '';
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: radial-gradient(circle at 0% 0%, rgba(79, 70, 229, 0.05) 0%, transparent 50%),
                radial-gradient(circle at 100% 100%, rgba(14, 165, 233, 0.05) 0%, transparent 50%);
    z-index: -1;
}

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

/* Sidebar */
.sidebar {
    width: 260px;
    background: var(--card-bg);
    border-right: 1px solid var(--border);
    padding: 2rem 1.5rem;
    display: flex;
    flex-direction: column;
    gap: 2rem;
    position: sticky;
    top: 0;
    height: 100vh;
}

.logo {
    font-size: 1.5rem;
    font-weight: 800;
    color: var(--primary);
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.nav-links {
    list-style: none;
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

.nav-item {
    padding: 0.75rem 1rem;
    border-radius: 0.75rem;
    cursor: pointer;
    transition: all 0.2s ease;
    display: flex;
    align-items: center;
    gap: 0.75rem;
    font-weight: 500;
    color: var(--text-muted);
}

.nav-item:hover {
    background: rgba(79, 70, 229, 0.1);
    color: var(--primary);
}

.nav-item.active {
    background: var(--primary);
    color: white;
}

/* Main Content */
.main-content {
    flex: 1;
    padding: 2rem;
    max-width: 1400px;
    margin: 0 auto;
    width: 100%;
}

header {
    margin-bottom: 2rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.title-group h1 {
    font-size: 1.875rem;
    font-weight: 700;
}

.title-group p {
    color: var(--text-muted);
}

/* Dashboard Stats */
.stats-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
    gap: 1.5rem;
    margin-bottom: 2.5rem;
}

.stat-card {
    background: var(--card-bg);
    padding: 1.5rem;
    border-radius: 1rem;
    border: 1px solid var(--border);
    box-shadow: var(--shadow);
    transition: transform 0.2s ease;
}

.stat-card:hover {
    transform: translateY(-5px);
}

.stat-label {
    color: var(--text-muted);
    font-size: 0.875rem;
    font-weight: 500;
}

.stat-value {
    font-size: 1.5rem;
    font-weight: 700;
    margin-top: 0.5rem;
}

/* Form Styling */
.glass-panel {
    background: var(--glass);
    backdrop-filter: blur(10px);
    border: 1px solid var(--border);
    padding: 2rem;
    border-radius: 1.5rem;
    box-shadow: var(--shadow);
}

.form-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 1.5rem;
}

.input-group {
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

label {
    font-size: 0.875rem;
    font-weight: 600;
    color: var(--text-main);
}

input, select, textarea {
    padding: 0.75rem 1rem;
    border-radius: 0.75rem;
    border: 1px solid var(--border);
    background: white;
    font-size: 1rem;
    transition: border-color 0.2s, box-shadow 0.2s;
}

input:focus {
    outline: none;
    border-color: var(--primary);
    box-shadow: 0 0 0 3px rgba(79, 70, 229, 0.1);
}

/* Items Table for Invoice */
.items-section {
    margin-top: 2rem;
}

.items-table {
    width: 100%;
    border-collapse: separate;
    border-spacing: 0 0.75rem;
}

.items-table th {
    text-align: left;
    padding: 1rem;
    color: var(--text-muted);
    font-weight: 600;
}

.items-table td {
    background: white;
    padding: 1rem;
    border-top: 1px solid var(--border);
    border-bottom: 1px solid var(--border);
}

.items-table td:first-child {
    border-left: 1px solid var(--border);
    border-radius: 0.75rem 0 0 0.75rem;
}

.items-table td:last-child {
    border-right: 1px solid var(--border);
    border-radius: 0 0.75rem 0.75rem 0;
}

/* Buttons */
.btn {
    padding: 0.75rem 1.5rem;
    border-radius: 0.75rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.2s ease;
    border: none;
    display: flex;
    align-items: center;
    gap: 0.5rem;
    justify-content: center;
}

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

.btn-primary:hover {
    background: var(--primary-hover);
    transform: scale(1.02);
}

.btn-outline {
    background: transparent;
    border: 1px solid var(--border);
    color: var(--text-main);
}

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

/* Invoice Modal/Preview */
.modal-overlay {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: rgba(0, 0, 0, 0.5);
    backdrop-filter: blur(4px);
    display: none;
    justify-content: center;
    align-items: center;
    z-index: 1000;
}

.invoice-preview {
    width: 800px;
    max-height: 90vh;
    background: white;
    border-radius: 1rem;
    padding: 3rem;
    overflow-y: auto;
}

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

.animate-fadeIn {
    animation: fadeIn 0.4s ease forwards;
}

/* Section Hiding */
.section {
    display: none;
}

.section.active {
    display: block;
}

/* Modern Invoice Print Styling */
@media print {
    body * { visibility: hidden; }
    #printable-invoice, #printable-invoice * { visibility: visible; }
    #printable-invoice {
        position: absolute;
        left: 0;
        top: 0;
        width: 100%;
        background: white !important;
        padding: 0 !important;
        margin: 0 !important;
    }
    .no-print { display: none !important; }
    .glass-panel { border: none !important; box-shadow: none !important; background: none !important; }
    
    @page { margin: 15mm; size: A4; }
    * { -webkit-print-color-adjust: exact !important; print-color-adjust: exact !important; }
    
    .print-header-bg { background: #f8fafc !important; border-bottom: 2px solid #1e40af !important; }
    .print-table-header { background: #1e40af !important; color: white !important; }
}

/* Payment Status Tags */
.status-paid { background: #dcfce7; color: #166534; }
.status-partial { background: #fef9c3; color: #854d0e; }
.status-unpaid { background: #fee2e2; color: #991b1b; }
.status-chip { padding: 0.25rem 0.6rem; border-radius: 1rem; font-size: 0.7rem; font-weight: 600; }