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

:root {
    --primary-color: #2563eb;
    --secondary-color: #64748b;
    --success-color: #10b981;
    --danger-color: #ef4444;
    --warning-color: #f59e0b;
    --bg-color: #f8fafc;
    --card-bg: #ffffff;
    --text-primary: #1e293b;
    --text-secondary: #64748b;
    --border-color: #e2e8f0;
    --shadow: 0 1px 3px 0 rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1);
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    background: var(--bg-color);
    color: var(--text-primary);
    line-height: 1.6;
    min-height: 100vh;
}

.container {
    max-width: 100%;
    margin: 0 auto;
    padding: 0;
}

header {
    background: var(--card-bg);
    padding: 1rem;
    box-shadow: var(--shadow);
    position: sticky;
    top: 0;
    z-index: 100;
}

header h1 {
    font-size: 1.5rem;
    color: var(--primary-color);
    margin-bottom: 0.5rem;
}

.status-bar {
    display: flex;
    justify-content: space-between;
    align-items: center;
    font-size: 0.875rem;
    color: var(--text-secondary);
}

#connectionStatus {
    padding: 0.25rem 0.75rem;
    background: var(--success-color);
    color: white;
    border-radius: 1rem;
    font-weight: 500;
}

main {
    padding: 1rem;
}

.tab-navigation {
    display: flex;
    gap: 0.5rem;
    margin-bottom: 1.5rem;
    border-bottom: 2px solid var(--border-color);
    overflow-x: auto;
}

.tab-button {
    padding: 0.75rem 1.5rem;
    background: none;
    border: none;
    color: var(--text-secondary);
    font-weight: 500;
    cursor: pointer;
    position: relative;
    white-space: nowrap;
    transition: color 0.3s;
}

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

.tab-button.active::after {
    content: '';
    position: absolute;
    bottom: -2px;
    left: 0;
    right: 0;
    height: 2px;
    background: var(--primary-color);
}

.tab-content {
    display: none;
}

.tab-content.active {
    display: block;
}

.scanner-section {
    background: var(--card-bg);
    padding: 1.5rem;
    border-radius: 0.5rem;
    margin-bottom: 1.5rem;
    box-shadow: var(--shadow);
}

.scanner-section h2 {
    margin-bottom: 1rem;
    color: var(--text-primary);
}

.qr-scanner {
    position: relative;
    width: 100%;
    max-width: 400px;
    margin: 0 auto 1rem;
    display: none;
}

.qr-scanner.active {
    display: block;
}

#scannerVideo, #scannerVideoReturn {
    width: 100%;
    border-radius: 0.5rem;
}

.scanner-overlay {
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    pointer-events: none;
}

.scanner-frame {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    width: 200px;
    height: 200px;
    border: 3px solid var(--primary-color);
    border-radius: 0.5rem;
    box-shadow: 0 0 0 10000px rgba(0, 0, 0, 0.5);
}

.scan-result {
    padding: 1rem;
    background: var(--success-color);
    color: white;
    border-radius: 0.5rem;
    margin-top: 1rem;
}

.scan-result.error {
    background: var(--danger-color);
}

.hidden {
    display: none !important;
}

.btn {
    padding: 0.75rem 1.5rem;
    border: none;
    border-radius: 0.5rem;
    font-weight: 500;
    cursor: pointer;
    transition: all 0.3s;
    font-size: 1rem;
    width: 100%;
}

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

.btn-primary:hover {
    background: #1d4ed8;
}

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

.btn-secondary:hover {
    background: #475569;
}

.key-details, .return-details {
    background: var(--card-bg);
    padding: 1.5rem;
    border-radius: 0.5rem;
    margin-bottom: 1.5rem;
    box-shadow: var(--shadow);
}

.detail-grid {
    display: grid;
    grid-template-columns: auto 1fr;
    gap: 1rem;
    margin-top: 1rem;
}

.detail-grid label {
    font-weight: 500;
    color: var(--text-secondary);
}

.detail-grid span {
    color: var(--text-primary);
}

.recipient-form {
    background: var(--card-bg);
    padding: 1.5rem;
    border-radius: 0.5rem;
    margin-bottom: 1.5rem;
    box-shadow: var(--shadow);
}

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

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

.form-group input,
.form-group textarea,
.form-group select {
    width: 100%;
    padding: 0.75rem;
    border: 1px solid var(--border-color);
    border-radius: 0.375rem;
    font-size: 1rem;
    transition: border-color 0.3s;
}

.form-group input:focus,
.form-group textarea:focus,
.form-group select:focus {
    outline: none;
    border-color: var(--primary-color);
}

.signature-section {
    background: var(--card-bg);
    padding: 1.5rem;
    border-radius: 0.5rem;
    margin-bottom: 1.5rem;
    box-shadow: var(--shadow);
}

#signatureCanvas, #returnSignatureCanvas {
    width: 100%;
    height: 200px;
    border: 2px dashed var(--border-color);
    border-radius: 0.5rem;
    background: white;
    touch-action: none;
    cursor: crosshair;
    display: block;
    user-select: none;
    -webkit-user-select: none;
    -moz-user-select: none;
    -ms-user-select: none;
    -webkit-touch-callout: none;
}

.signature-controls {
    display: grid;
    grid-template-columns: 1fr 2fr;
    gap: 1rem;
    margin-top: 1rem;
}

.management-section {
    background: var(--card-bg);
    padding: 1.5rem;
    border-radius: 0.5rem;
    margin-bottom: 1.5rem;
    box-shadow: var(--shadow);
}

.management-section h3 {
    margin-bottom: 1rem;
    color: var(--text-primary);
}

.filter-controls {
    display: grid;
    grid-template-columns: 1fr auto;
    gap: 1rem;
    margin-bottom: 1rem;
}

#searchInput {
    padding: 0.75rem;
    border: 1px solid var(--border-color);
    border-radius: 0.375rem;
    font-size: 1rem;
}

#statusFilter {
    padding: 0.75rem;
    border: 1px solid var(--border-color);
    border-radius: 0.375rem;
    font-size: 1rem;
    background: white;
}

.table-container {
    overflow-x: auto;
    -webkit-overflow-scrolling: touch;
}

table {
    width: 100%;
    border-collapse: collapse;
    min-width: 600px;
}

thead {
    background: var(--bg-color);
}

th {
    padding: 0.75rem;
    text-align: left;
    font-weight: 500;
    color: var(--text-secondary);
    border-bottom: 2px solid var(--border-color);
}

td {
    padding: 0.75rem;
    border-bottom: 1px solid var(--border-color);
}

tbody tr:hover {
    background: var(--bg-color);
}

.status-badge {
    display: inline-block;
    padding: 0.25rem 0.75rem;
    border-radius: 1rem;
    font-size: 0.875rem;
    font-weight: 500;
}

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

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

.action-btn {
    padding: 0.5rem 1rem;
    border: none;
    border-radius: 0.375rem;
    font-size: 0.875rem;
    cursor: pointer;
    background: var(--primary-color);
    color: white;
}

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

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

.modal-content {
    background: var(--card-bg);
    padding: 2rem;
    border-radius: 0.5rem;
    max-width: 90%;
    max-height: 90%;
    overflow-y: auto;
    position: relative;
}

.modal-close {
    position: absolute;
    top: 1rem;
    right: 1rem;
    font-size: 2rem;
    cursor: pointer;
    color: var(--text-secondary);
}

input[type="file"] {
    margin-bottom: 1rem;
}

@media (max-width: 768px) {
    header h1 {
        font-size: 1.25rem;
    }
    
    .tab-button {
        padding: 0.5rem 1rem;
        font-size: 0.875rem;
    }
    
    .signature-controls {
        grid-template-columns: 1fr;
    }
    
    .filter-controls {
        grid-template-columns: 1fr;
    }
    
    .detail-grid {
        grid-template-columns: 1fr;
    }
    
    .detail-grid label {
        font-weight: 600;
        margin-top: 0.5rem;
    }
}

@media (min-width: 1024px) {
    .container {
        max-width: 1200px;
        padding: 2rem;
    }

    main {
        padding: 2rem;
    }

    .qr-scanner {
        max-width: 500px;
    }

    .signature-controls {
        grid-template-columns: 1fr 1fr 2fr;
    }
}

.paste-area {
    width: 100%;
    min-height: 150px;
    padding: 1rem;
    border: 2px dashed var(--border-color);
    border-radius: 0.5rem;
    font-family: monospace;
    font-size: 0.875rem;
    resize: vertical;
    background: var(--bg-color);
    transition: border-color 0.3s;
}

.paste-area:focus {
    outline: none;
    border-color: var(--primary-color);
    background: white;
}

.import-info {
    margin-bottom: 1rem;
    color: var(--text-secondary);
    font-size: 0.875rem;
}

.import-preview {
    margin-top: 1rem;
    padding: 1rem;
    background: var(--bg-color);
    border-radius: 0.5rem;
}

.import-preview h4 {
    margin-bottom: 0.75rem;
    color: var(--text-primary);
    font-size: 1rem;
}

.preview-table {
    width: 100%;
    border-collapse: collapse;
    background: white;
    border-radius: 0.5rem;
    overflow: hidden;
}

.preview-table th {
    background: var(--bg-color);
    padding: 0.75rem;
    text-align: left;
    font-weight: 600;
    font-size: 0.875rem;
    color: var(--text-primary);
    border-bottom: 2px solid var(--border-color);
}

.preview-table td {
    padding: 0.75rem;
    border-bottom: 1px solid var(--border-color);
    font-size: 0.875rem;
}

.preview-table tbody tr:hover {
    background: var(--bg-color);
}

.preview-table tbody tr:last-child td {
    border-bottom: none;
}

.import-buttons {
    margin-top: 1rem;
    display: flex;
    gap: 0.75rem;
    justify-content: flex-end;
}

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

.btn-danger:hover {
    background: #dc2626;
}

.action-buttons {
    display: flex;
    gap: 0.5rem;
    flex-wrap: nowrap;
}

.action-btn {
    padding: 0.375rem 0.75rem;
    font-size: 0.8rem;
    border: none;
    border-radius: 0.25rem;
    cursor: pointer;
    transition: background-color 0.2s;
    white-space: nowrap;
}

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

.action-btn.btn-danger:hover {
    background: #dc2626;
}

.action-btn:not(.btn-danger) {
    background: var(--secondary-color);
    color: white;
}

.action-btn:not(.btn-danger):hover {
    background: #475569;
}

.history-table-container {
    max-height: 400px;
    overflow-y: auto;
    margin-top: 1rem;
}

.history-table {
    width: 100%;
    border-collapse: collapse;
    font-size: 0.875rem;
}

.history-table th {
    background: var(--bg-color);
    padding: 0.75rem;
    text-align: left;
    font-weight: 600;
    border-bottom: 2px solid var(--border-color);
    position: sticky;
    top: 0;
}

.history-table td {
    padding: 0.75rem;
    border-bottom: 1px solid var(--border-color);
    vertical-align: middle;
}

.history-table tbody tr:hover {
    background: var(--bg-color);
}

.signature-preview {
    max-width: 80px;
    max-height: 40px;
    cursor: pointer;
    border: 1px solid var(--border-color);
    border-radius: 0.25rem;
    transition: transform 0.2s;
}

.signature-preview:hover {
    transform: scale(1.1);
    box-shadow: var(--shadow);
}

.no-signature {
    color: var(--text-secondary);
    font-style: italic;
    font-size: 0.8rem;
}

.delete-disabled {
    padding: 0.375rem 0.75rem;
    font-size: 0.8rem;
    color: var(--text-secondary);
    background: var(--border-color);
    border-radius: 0.25rem;
    cursor: not-allowed;
    white-space: nowrap;
}