.center-container {
    max-width: 1200px;
    margin: 40px auto;
    padding: 30px;
    background: #fff;
    box-shadow: 0 10px 30px rgba(0, 0, 0, 0.1);
    border-radius: 16px;
    display: flex;
    gap: 30px;
    min-height: 800px;
}

.kdm-sidebar {
    width: 300px;
    background: #f8f9fa;
    border-radius: 12px;
    padding: 20px;
    display: flex;
    flex-direction: column;
    gap: 15px;
    border: 1px solid #e9ecef;
}

.sidebar-title {
    font-size: 1.2rem;
    font-weight: 700;
    color: #1a2a3a;
    margin-bottom: 10px;
    padding-bottom: 10px;
    border-bottom: 2px solid #007bff;
}

.doc-list {
    list-style: none;
    padding: 0;
    margin: 0;
    display: flex;
    flex-direction: column;
    gap: 8px;
    flex-grow: 1;
    overflow-y: auto;
}

.doc-item {
    padding: 12px 15px;
    background: #fff;
    border: 1px solid #dee2e6;
    border-radius: 8px;
    cursor: pointer;
    transition: all 0.2s;
    font-weight: 500;
    color: #495057;
    display: flex;
    align-items: center;
    gap: 10px;
}

.doc-item:hover {
    border-color: #007bff;
    background: #e7f1ff;
    color: #007bff;
    transform: translateX(5px);
}

.doc-item.active {
    background: #007bff;
    color: #fff;
    border-color: #007bff;
    box-shadow: 0 4px 10px rgba(0, 123, 255, 0.2);
}

.doc-icon {
    font-size: 1.1rem;
}

.kdm-viewer-container {
    flex-grow: 1;
    display: flex;
    flex-direction: column;
    gap: 20px;
}

.viewer-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding-bottom: 15px;
    border-bottom: 1px solid #eee;
}

.current-title {
    font-size: 1.5rem;
    font-weight: 700;
    color: #2b3e50;
    margin: 0;
}

.pdf-container {
    width: 100%;
    height: 850px;
    border: 1px solid #dee2e6;
    border-radius: 12px;
    background: #f1f3f5;
    overflow: hidden;
    position: relative;
}

.pdf-viewer {
    width: 100%;
    height: 100%;
    border: none;
}

.viewer-actions {
    display: flex;
    gap: 15px;
}

.btn-action {
    padding: 10px 20px;
    border-radius: 6px;
    text-decoration: none;
    font-weight: 600;
    font-size: 0.9rem;
    display: flex;
    align-items: center;
    gap: 8px;
    transition: all 0.2s;
}

.btn-download {
    background: #007bff;
    color: #fff;
}

.btn-download:hover {
    background: #0056b3;
}

.btn-open {
    background: #6c757d;
    color: #fff;
}

.btn-open:hover {
    background: #5a6268;
}

@media (max-width: 992px) {
    .center-container {
        flex-direction: column;
    }

    .kdm-sidebar {
        width: 100%;
        max-height: 250px;
    }
}

@media (max-width: 768px) {
    .center-container {
        padding: 15px;
        margin: 20px 10px;
    }

    .current-title {
        font-size: 1.2rem;
    }

    .pdf-container {
        height: 500px;
    }
}