:root {
    --primary: #4361ee;
    --primary-light: #4895ef;
    --secondary: #3f37c9;
    --success: #10b981;
    --warning: #f59e0b;
    --danger: #ef4444;
    --light: #f8f9fa;
    --dark: #212529;
    --gray: #6c757d;
    --gray-light: #e9ecef;
    --border-radius: 12px;
    --box-shadow: 0 5px 15px rgba(0, 0, 0, 0.08);
    --transition: all 0.3s ease;
    
    /* Legacy compatibility */
    --primary-color: #4361ee;
    --secondary-color: #64748b;
    --success-color: #10b981;
    --danger-color: #ef4444;
    --warning-color: #f59e0b;
    --bg-color: #f8fafc;
    --card-bg: #ffffff;
    --text-color: #212529;
    --border-color: #e9ecef;
}

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

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background: linear-gradient(135deg, #f5f7fa 0%, #c3cfe2 100%);
    min-height: 100vh;
    color: var(--dark);
    line-height: 1.6;
    padding: 20px;
}

.container {
    max-width: 1400px;
    margin: 0 auto;
    padding: 0;
}

header {
    text-align: center;
    padding: 25px;
    background: white;
    color: var(--dark);
    border-radius: var(--border-radius);
    margin-bottom: 25px;
    box-shadow: var(--box-shadow);
}

header h1 {
    font-size: 2rem;
    margin-bottom: 5px;
    color: var(--primary);
}

.subtitle {
    font-size: 1rem;
    color: var(--gray);
}

.tabs {
    display: flex;
    gap: 10px;
    margin-bottom: 20px;
    overflow-x: auto;
    padding-bottom: 10px;
}

.tab-button {
    background: white;
    border: none;
    padding: 12px 20px;
    border-radius: 8px;
    font-weight: 600;
    cursor: pointer;
    transition: var(--transition);
    white-space: nowrap;
    box-shadow: 0 2px 5px rgba(0, 0, 0, 0.05);
    color: var(--gray);
    font-size: 1rem;
}

.tab-button:hover {
    background: var(--gray-light);
    transform: translateY(-2px);
}

.tab-button.active {
    background: var(--primary);
    color: white;
}

.tab-content {
    display: none;
}

.tab-content.active {
    display: block;
    animation: fadeIn 0.5s ease;
}

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

h2 {
    margin-bottom: 20px;
    color: var(--primary);
    font-size: 1.5rem;
}

h3 {
    margin-bottom: 15px;
    color: var(--dark);
    font-size: 1.2rem;
    display: flex;
    align-items: center;
    gap: 10px;
}

.form-section {
    background: white;
    border-radius: var(--border-radius);
    padding: 25px;
    box-shadow: var(--box-shadow);
    margin-bottom: 25px;
}

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

label {
    display: block;
    margin-bottom: 8px;
    font-weight: 600;
    color: var(--dark);
}

input[type="text"],
input[type="email"],
input[type="tel"],
input[type="number"],
input[type="password"],
input[type="date"],
select,
textarea {
    width: 100%;
    padding: 12px 15px;
    border: 1px solid var(--gray-light);
    border-radius: 8px;
    font-size: 1rem;
    transition: var(--transition);
}

input:focus,
select:focus,
textarea:focus {
    outline: none;
    border-color: var(--primary);
    box-shadow: 0 0 0 3px rgba(67, 97, 238, 0.2);
}

.item-row {
    display: grid;
    grid-template-columns: 2fr 1fr 1fr auto;
    gap: 10px;
    margin-bottom: 10px;
    align-items: center;
}

.btn-primary,
.btn-secondary,
.btn-remove {
    padding: 12px 25px;
    border: none;
    border-radius: 8px;
    font-size: 1rem;
    cursor: pointer;
    transition: var(--transition);
    font-weight: 600;
}

.btn-primary {
    background: var(--primary);
    color: white;
    width: 100%;
    margin-top: 20px;
}

.btn-primary:hover {
    background: var(--secondary);
    transform: translateY(-2px);
    box-shadow: 0 4px 12px rgba(67, 97, 238, 0.3);
}

.btn-secondary {
    background: var(--gray-light);
    color: var(--dark);
}

.btn-secondary:hover {
    background: #d1d5db;
    transform: translateY(-2px);
}

.btn-remove {
    background: var(--danger);
    color: white;
    padding: 8px 12px;
    width: 35px;
    height: 35px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
}

.btn-remove:hover {
    background: #dc2626;
    transform: scale(1.1);
}

.total-section {
    background: var(--primary-color);
    color: white;
    padding: 20px;
    border-radius: 8px;
    text-align: center;
    margin: 20px 0;
}

.total-section h3 {
    color: white;
    font-size: 1.8rem;
}

.invoice-card {
    background: var(--bg-color);
    padding: 20px;
    margin-bottom: 15px;
    border-radius: 8px;
    border-left: 4px solid var(--primary-color);
}

.invoice-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 10px;
}

.invoice-number {
    font-weight: 700;
    font-size: 1.2rem;
    color: var(--primary-color);
}

.status-badge {
    padding: 6px 12px;
    border-radius: 20px;
    font-size: 0.85rem;
    font-weight: 600;
    text-transform: uppercase;
}

.status-pending {
    background: #fef3c7;
    color: #92400e;
}

.status-paid {
    background: #d1fae5;
    color: #065f46;
}

.status-cancelled {
    background: #fee2e2;
    color: #991b1b;
}

.invoice-details {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 15px;
    margin-top: 15px;
}

.detail-item {
    display: flex;
    flex-direction: column;
}

.detail-label {
    font-size: 0.85rem;
    color: var(--secondary-color);
    margin-bottom: 4px;
}

.detail-value {
    font-weight: 500;
}

.invoice-actions {
    display: flex;
    gap: 10px;
    margin-top: 15px;
    flex-wrap: wrap;
}

.action-group {
    position: relative;
    display: inline-block;
}

.dropdown-toggle {
    padding: 8px 16px;
    font-size: 0.9rem;
    background: var(--secondary-color);
    color: white;
    border: none;
    border-radius: 6px;
    cursor: pointer;
    transition: all 0.3s;
    display: flex;
    align-items: center;
    gap: 5px;
}

.dropdown-toggle:hover {
    background: #475569;
}

.dropdown-toggle::after {
    content: '▼';
    font-size: 0.7rem;
}

.dropdown-menu {
    display: none;
    position: absolute;
    top: 100%;
    left: 0;
    background: white;
    min-width: 200px;
    box-shadow: 0 4px 12px rgba(0,0,0,0.15);
    border-radius: 6px;
    margin-top: 5px;
    z-index: 100;
    overflow: hidden;
}

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

.dropdown-menu button {
    width: 100%;
    padding: 10px 15px;
    border: none;
    background: white;
    text-align: left;
    cursor: pointer;
    transition: background 0.2s;
    font-size: 0.9rem;
    color: var(--text-color);
    border-bottom: 1px solid var(--border-color);
}

.dropdown-menu button:last-child {
    border-bottom: none;
}

.dropdown-menu button:hover {
    background: var(--bg-color);
}

.btn-small {
    padding: 8px 16px;
    font-size: 0.9rem;
}

.actions {
    margin-bottom: 20px;
}

.modal {
    display: none;
    position: fixed;
    z-index: 1000;
    left: 0;
    top: 0;
    width: 100%;
    height: 100%;
    background-color: rgba(0,0,0,0.5);
    overflow-y: auto;
    align-items: center;
    justify-content: center;
}

.modal-content {
    background-color: var(--card-bg);
    margin: 50px auto;
    padding: 30px;
    border-radius: 12px;
    width: 90%;
    max-width: 500px;
    max-height: 90vh;
    overflow-y: auto;
    box-shadow: 0 10px 25px rgba(0,0,0,0.2);
    position: relative;
}

.close {
    color: var(--secondary-color);
    float: right;
    font-size: 28px;
    font-weight: bold;
    cursor: pointer;
}

.close:hover {
    color: var(--danger-color);
}

.alert {
    padding: 15px;
    border-radius: 6px;
    margin: 15px 0;
}

.alert-success {
    background: #d1fae5;
    color: #065f46;
    border-left: 4px solid var(--success-color);
}

.alert-error {
    background: #fee2e2;
    color: #991b1b;
    border-left: 4px solid var(--danger-color);
}

.alert-info {
    background: #dbeafe;
    color: #1e40af;
    border-left: 4px solid var(--primary-color);
}

@media (max-width: 768px) {
    .item-row {
        grid-template-columns: 1fr;
    }
    
    .invoice-header {
        flex-direction: column;
        align-items: flex-start;
    }
    
    .tabs {
        flex-direction: column;
    }
}