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

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, sans-serif;
    background: #f5f7fa;
    color: #2c3e50;
}

.container {
    display: flex;
    min-height: 100vh;
}

/* Sidebar Navigation */
.sidebar {
    width: 250px;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    padding: 20px 0;
    position: fixed;
    height: 100vh;
    overflow-y: auto;
}

.logo {
    padding: 0 20px 30px;
    border-bottom: 1px solid rgba(255, 255, 255, 0.2);
}

.logo h2 {
    font-size: 24px;
    font-weight: 600;
}

.nav-menu {
    list-style: none;
    margin-top: 20px;
}

.nav-item {
    padding: 15px 20px;
    cursor: pointer;
    transition: all 0.3s;
    display: flex;
    align-items: center;
    gap: 12px;
}

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

.nav-item.active {
    background: rgba(255, 255, 255, 0.2);
    border-left: 4px solid white;
}

.icon {
    font-size: 20px;
}

/* Main Content */
.main-content {
    margin-left: 250px;
    flex: 1;
    padding: 30px;
    width: calc(100% - 250px);
}

.page {
    display: none;
}

.page.active {
    display: block;
}

.page-header {
    margin-bottom: 30px;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.page-header h1 {
    font-size: 32px;
    color: #2c3e50;
}

.subtitle {
    color: #7f8c8d;
    margin-top: 5px;
}

/* Cards */
.card {
    background: white;
    border-radius: 10px;
    padding: 25px;
    box-shadow: 0 2px 10px rgba(0, 0, 0, 0.05);
    margin-bottom: 20px;
}

.card h2 {
    margin-bottom: 20px;
    color: #2c3e50;
    font-size: 20px;
}

/* Stats Grid */
.stats-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 20px;
    margin-bottom: 30px;
}

.stat-card {
    background: white;
    border-radius: 10px;
    padding: 25px;
    box-shadow: 0 2px 10px rgba(0, 0, 0, 0.05);
    display: flex;
    align-items: center;
    gap: 20px;
}

.stat-icon {
    font-size: 40px;
    width: 70px;
    height: 70px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    border-radius: 10px;
}

.stat-info {
    flex: 1;
}

.stat-label {
    color: #7f8c8d;
    font-size: 14px;
    margin-bottom: 5px;
}

.stat-value {
    font-size: 28px;
    font-weight: 600;
    color: #2c3e50;
}

/* Buttons */
.btn {
    padding: 10px 20px;
    border: none;
    border-radius: 6px;
    cursor: pointer;
    font-size: 14px;
    font-weight: 500;
    transition: all 0.3s;
}

.btn-primary {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
}

.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: 0 5px 15px rgba(102, 126, 234, 0.4);
}

.btn-secondary {
    background: #95a5a6;
    color: white;
}

.btn-secondary:hover {
    background: #7f8c8d;
}

.btn-danger {
    background: #e74c3c;
    color: white;
    padding: 6px 12px;
    font-size: 12px;
}

.btn-danger:hover {
    background: #c0392b;
}

.btn-edit {
    background: #3498db;
    color: white;
    padding: 6px 12px;
    font-size: 12px;
    margin-right: 5px;
}

.btn-edit:hover {
    background: #2980b9;
}

.btn-block {
    width: 100%;
    margin-top: 20px;
}

/* Tables */
.data-table {
    width: 100%;
    border-collapse: collapse;
}

.data-table thead {
    background: #f8f9fa;
}

.data-table th {
    padding: 15px;
    text-align: left;
    font-weight: 600;
    color: #2c3e50;
    border-bottom: 2px solid #e9ecef;
}

.data-table td {
    padding: 15px;
    border-bottom: 1px solid #e9ecef;
}

.data-table tbody tr:hover {
    background: #f8f9fa;
}

/* Forms */
.form-group {
    margin-bottom: 20px;
}

.form-group label {
    display: block;
    margin-bottom: 8px;
    font-weight: 500;
    color: #2c3e50;
}

.form-group input,
.form-group select {
    width: 100%;
    padding: 10px;
    border: 2px solid #e9ecef;
    border-radius: 6px;
    font-size: 14px;
    transition: border 0.3s;
}

.form-group input:focus,
.form-group select:focus {
    outline: none;
    border-color: #667eea;
}

.form-actions {
    display: flex;
    gap: 10px;
    justify-content: flex-end;
    margin-top: 20px;
}

/* Modal */
.modal {
    display: none;
    position: fixed;
    z-index: 1000;
    left: 0;
    top: 0;
    width: 100%;
    height: 100%;
    background: rgba(0, 0, 0, 0.5);
    animation: fadeIn 0.3s;
}

@keyframes fadeIn {
    from { opacity: 0; }
    to { opacity: 1; }
}

.modal-content {
    background: white;
    margin: 50px auto;
    padding: 30px;
    border-radius: 10px;
    width: 90%;
    max-width: 500px;
    position: relative;
    animation: slideDown 0.3s;
}

@keyframes slideDown {
    from {
        transform: translateY(-50px);
        opacity: 0;
    }
    to {
        transform: translateY(0);
        opacity: 1;
    }
}

.close {
    position: absolute;
    right: 20px;
    top: 20px;
    font-size: 28px;
    font-weight: bold;
    color: #aaa;
    cursor: pointer;
}

.close:hover {
    color: #000;
}

/* Billing */
.billing-container {
    max-width: 600px;
}

.bill-items {
    margin: 20px 0;
}

.bill-item {
    display: flex;
    justify-content: space-between;
    padding: 10px;
    background: #f8f9fa;
    border-radius: 6px;
    margin-bottom: 10px;
}

.bill-item-info {
    flex: 1;
}

.bill-item-remove {
    color: #e74c3c;
    cursor: pointer;
    font-weight: bold;
}

.bill-total {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    padding: 20px;
    border-radius: 6px;
    text-align: center;
    margin: 20px 0;
}

/* Recent Bills */
.recent-bills,
.all-bills {
    max-height: 400px;
    overflow-y: auto;
}

.bill-card {
    background: #f8f9fa;
    padding: 15px;
    border-radius: 6px;
    margin-bottom: 10px;
    border-left: 4px solid #667eea;
}

.bill-header {
    display: flex;
    justify-content: space-between;
    margin-bottom: 10px;
}

.bill-id {
    font-weight: 600;
    color: #2c3e50;
}

.bill-date {
    color: #7f8c8d;
    font-size: 14px;
}

.bill-customer {
    color: #2c3e50;
    margin-bottom: 5px;
}

.bill-amount {
    font-size: 18px;
    font-weight: 600;
    color: #667eea;
}

/* Responsive */
@media (max-width: 768px) {
    .sidebar {
        width: 70px;
    }
    
    .sidebar .logo h2 {
        display: none;
    }
    
    .nav-item {
        justify-content: center;
    }
    
    .nav-item span:not(.icon) {
        display: none;
    }
    
    .main-content {
        margin-left: 70px;
        width: calc(100% - 70px);
    }
    
    .stats-grid {
        grid-template-columns: 1fr;
    }
    
    .page-header {
        flex-direction: column;
        align-items: flex-start;
        gap: 15px;
    }
}

.empty-state {
    text-align: center;
    padding: 40px;
    color: #7f8c8d;
}