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

:root {
    --primary: #2563eb;
    --primary-dark: #1d4ed8;
    --danger: #dc2626;
    --success: #16a34a;
    --gray-50: #f9fafb;
    --gray-100: #f3f4f6;
    --gray-200: #e5e7eb;
    --gray-300: #d1d5db;
    --gray-600: #4b5563;
    --gray-800: #1f2937;
    --gray-900: #111827;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    background: var(--gray-50);
    color: var(--gray-800);
    line-height: 1.6;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 2rem;
}

/* Navbar */
.navbar {
    background: var(--gray-900);
    color: white;
    padding: 1rem 2rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.nav-brand {
    font-size: 1.25rem;
    font-weight: 600;
}

.nav-links {
    display: flex;
    gap: 1.5rem;
}

.nav-links a {
    color: var(--gray-300);
    text-decoration: none;
    transition: color 0.2s;
}

.nav-links a:hover {
    color: white;
}

.nav-links .logout {
    color: var(--danger);
}

/* Buttons */
.btn {
    display: inline-block;
    padding: 0.5rem 1rem;
    border: none;
    border-radius: 0.375rem;
    font-size: 0.875rem;
    font-weight: 500;
    cursor: pointer;
    text-decoration: none;
    transition: all 0.2s;
}

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

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

.btn-secondary {
    background: var(--gray-200);
    color: var(--gray-800);
}

.btn-secondary:hover {
    background: var(--gray-300);
}

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

.btn-sm {
    padding: 0.25rem 0.5rem;
    font-size: 0.75rem;
}

.btn-large {
    padding: 0.75rem 1.5rem;
    font-size: 1rem;
}

.btn-full {
    width: 100%;
}

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

.form-group label {
    display: block;
    margin-bottom: 0.25rem;
    font-weight: 500;
    color: var(--gray-600);
}

.form-group input,
.form-group select {
    width: 100%;
    padding: 0.5rem 0.75rem;
    border: 1px solid var(--gray-300);
    border-radius: 0.375rem;
    font-size: 1rem;
}

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

/* Alerts */
.alert {
    padding: 0.75rem 1rem;
    border-radius: 0.375rem;
    margin-bottom: 1rem;
}

.alert-error {
    background: #fef2f2;
    color: var(--danger);
    border: 1px solid #fecaca;
}

/* Hero */
.hero {
    background: linear-gradient(135deg, var(--primary) 0%, var(--primary-dark) 100%);
    color: white;
    padding: 4rem 2rem;
    text-align: center;
}

.hero h1 {
    font-size: 2.5rem;
    margin-bottom: 1rem;
}

.hero p {
    font-size: 1.25rem;
    opacity: 0.9;
    margin-bottom: 2rem;
}

.hero-buttons {
    display: flex;
    gap: 1rem;
    justify-content: center;
}

.hero .btn-secondary {
    background: rgba(255,255,255,0.2);
    color: white;
}

/* Features */
.features {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 2rem;
    padding: 3rem 2rem;
    max-width: 1000px;
    margin: 0 auto;
}

.feature {
    text-align: center;
    padding: 1.5rem;
}

.feature h3 {
    margin-bottom: 0.5rem;
    color: var(--gray-900);
}

.feature p {
    color: var(--gray-600);
}

/* Auth */
.auth-container {
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 2rem;
}

.auth-box {
    background: white;
    padding: 2rem;
    border-radius: 0.5rem;
    box-shadow: 0 4px 6px rgba(0,0,0,0.1);
    width: 100%;
    max-width: 400px;
}

.auth-box h1 {
    margin-bottom: 1.5rem;
    text-align: center;
}

.auth-link {
    text-align: center;
    margin-top: 1rem;
    color: var(--gray-600);
}

.auth-link a {
    color: var(--primary);
}

/* Dashboard */
.dashboard h1 {
    margin-bottom: 2rem;
}

.stats-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 1.5rem;
    margin-bottom: 2rem;
}

.stat-card {
    background: white;
    padding: 1.5rem;
    border-radius: 0.5rem;
    box-shadow: 0 1px 3px rgba(0,0,0,0.1);
}

.stat-card h3 {
    color: var(--gray-600);
    font-size: 0.875rem;
    font-weight: 500;
}

.stat-number {
    font-size: 2rem;
    font-weight: 700;
    color: var(--gray-900);
    margin: 0.5rem 0;
}

.stat-link {
    color: var(--primary);
    text-decoration: none;
    font-size: 0.875rem;
}

.quick-actions {
    background: white;
    padding: 1.5rem;
    border-radius: 0.5rem;
    box-shadow: 0 1px 3px rgba(0,0,0,0.1);
}

.quick-actions h2 {
    margin-bottom: 1rem;
    font-size: 1.125rem;
}

.action-buttons {
    display: flex;
    gap: 1rem;
}

/* Page Header */
.page-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 1.5rem;
}

/* Tables */
.data-table {
    width: 100%;
    background: white;
    border-radius: 0.5rem;
    overflow: hidden;
    box-shadow: 0 1px 3px rgba(0,0,0,0.1);
}

.data-table th,
.data-table td {
    padding: 0.75rem 1rem;
    text-align: left;
}

.data-table th {
    background: var(--gray-100);
    font-weight: 600;
    color: var(--gray-600);
    font-size: 0.875rem;
}

.data-table tr:not(:last-child) {
    border-bottom: 1px solid var(--gray-200);
}

.data-table .actions {
    display: flex;
    gap: 0.5rem;
}

/* Empty State */
.empty-state {
    text-align: center;
    padding: 3rem;
    background: white;
    border-radius: 0.5rem;
    box-shadow: 0 1px 3px rgba(0,0,0,0.1);
}

.empty-state p {
    color: var(--gray-600);
    margin-bottom: 1rem;
}

/* Form Page */
.form-page {
    max-width: 500px;
    margin: 0 auto;
}

.form-page h1 {
    margin-bottom: 1.5rem;
}

.form-card {
    background: white;
    padding: 1.5rem;
    border-radius: 0.5rem;
    box-shadow: 0 1px 3px rgba(0,0,0,0.1);
}

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

/* Sale Page */
.sale-page h1 {
    margin-bottom: 1.5rem;
}

.products-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(180px, 1fr));
    gap: 1rem;
    margin-bottom: 1.5rem;
}

.product-card {
    background: white;
    padding: 1rem;
    border-radius: 0.5rem;
    box-shadow: 0 1px 3px rgba(0,0,0,0.1);
    text-align: center;
}

.product-card h3 {
    font-size: 1rem;
    margin-bottom: 0.25rem;
}

.product-price {
    color: var(--gray-600);
    font-size: 0.875rem;
    margin-bottom: 0.75rem;
}

.quantity-control {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0.5rem;
}

.qty-btn {
    width: 32px;
    height: 32px;
    border: 1px solid var(--gray-300);
    background: white;
    border-radius: 0.25rem;
    cursor: pointer;
    font-size: 1.25rem;
    display: flex;
    align-items: center;
    justify-content: center;
}

.qty-btn:hover {
    background: var(--gray-100);
}

.qty-input {
    width: 50px;
    text-align: center;
    padding: 0.25rem;
    border: 1px solid var(--gray-300);
    border-radius: 0.25rem;
}

.sale-summary {
    background: white;
    padding: 1.5rem;
    border-radius: 0.5rem;
    box-shadow: 0 1px 3px rgba(0,0,0,0.1);
    max-width: 400px;
}

.total {
    display: flex;
    justify-content: space-between;
    font-size: 1.5rem;
    font-weight: 700;
    margin-bottom: 1rem;
    padding-bottom: 1rem;
    border-bottom: 2px solid var(--gray-200);
}

/* Receipt */
.receipt-page {
    max-width: 400px;
    margin: 0 auto;
}

.receipt {
    background: white;
    padding: 2rem;
    border-radius: 0.5rem;
    box-shadow: 0 1px 3px rgba(0,0,0,0.1);
}

.receipt-header {
    text-align: center;
    margin-bottom: 1.5rem;
    padding-bottom: 1rem;
    border-bottom: 1px dashed var(--gray-300);
}

.receipt-header h1 {
    font-size: 1.5rem;
}

.receipt-header p {
    color: var(--gray-600);
    font-size: 0.875rem;
}

.receipt-meta {
    margin-bottom: 1rem;
    font-size: 0.875rem;
}

.receipt-meta p {
    margin-bottom: 0.25rem;
}

.receipt-items {
    width: 100%;
    margin-bottom: 1rem;
    font-size: 0.875rem;
}

.receipt-items th,
.receipt-items td {
    padding: 0.5rem 0;
    text-align: left;
}

.receipt-items th {
    border-bottom: 1px solid var(--gray-300);
}

.receipt-items td:last-child,
.receipt-items th:last-child {
    text-align: right;
}

.receipt-total {
    text-align: right;
    font-size: 1.25rem;
    padding-top: 1rem;
    border-top: 2px solid var(--gray-800);
}

.receipt-footer {
    text-align: center;
    margin-top: 1.5rem;
    padding-top: 1rem;
    border-top: 1px dashed var(--gray-300);
    color: var(--gray-600);
}

.receipt-actions {
    display: flex;
    gap: 0.5rem;
    margin-top: 1.5rem;
    flex-wrap: wrap;
}

/* Responsive */
@media (max-width: 768px) {
    .navbar {
        flex-direction: column;
        gap: 1rem;
    }

    .nav-links {
        flex-wrap: wrap;
        justify-content: center;
    }

    .page-header {
        flex-direction: column;
        gap: 1rem;
        align-items: flex-start;
    }

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