body {
    margin: 0;
    padding: 0;
    display: flex;
    height: 100vh;
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
    background-color: #f5f5f5;
}
#sidebar {
    width: 320px;
    flex-shrink: 0;
    background: #ffffff;
    padding: 20px;
    box-shadow: 2px 0 5px rgba(0,0,0,0.1);
    z-index: 10;
    overflow-y: auto;
    display: flex;
    flex-direction: column;
}
#viewer {
    flex-grow: 1;
    min-width: 0;
    overflow: hidden;
    position: relative;
    background: #e0e0e0;
}
h2 {
    margin-top: 0;
    font-size: 1.2rem;
    color: #333;
}
.form-group {
    margin-bottom: 12px;
}
label {
    display: block;
    margin-bottom: 4px;
    font-weight: 500;
    font-size: 0.9rem;
    color: #555;
}
input[type="number"], select {
    width: 100%;
    padding: 8px;
    border: 1px solid #ccc;
    border-radius: 4px;
    box-sizing: border-box;
    background-color: #fff;
}
.section-title {
    margin-top: 15px;
    margin-bottom: 10px;
    padding-bottom: 5px;
    border-bottom: 2px solid #eee;
    font-weight: bold;
    color: #444;
}
button {
    width: 100%;
    padding: 10px;
    margin-top: 10px;
    background-color: #007bff;
    color: white;
    border: none;
    border-radius: 4px;
    cursor: pointer;
    font-weight: bold;
    transition: background 0.2s;
}
button:hover {
    background-color: #0056b3;
}
#btn-download {
    background-color: #28a745;
}
#btn-download:hover {
    background-color: #1e7e34;
}
#btn-reset {
    background-color: #6c757d;
}
#btn-reset:hover {
    background-color: #545b62;
}
#btn-collapse {
    width: auto;
    padding: 4px 8px;
    margin: 0;
    font-size: 0.75rem;
    background: #6c757d;
}
#btn-collapse:hover {
    background: #545b62;
}
#btn-expand {
    position: absolute;
    top: 10px;
    left: 10px;
    width: auto;
    padding: 6px 10px;
    margin: 0;
    font-size: 0.85rem;
    background: #6c757d;
    z-index: 20;
    display: none;
}
#btn-expand:hover {
    background: #545b62;
}
body.sidebar-collapsed #sidebar {
    display: none;
}
body.sidebar-collapsed #btn-expand {
    display: block;
}
#btn-engrave {
    background-color: #6f42c1;
}
#btn-engrave:hover {
    background-color: #59359a;
}