*{box-sizing:border-box}body{margin:0;font-family:system-ui,sans-serif}.app-shell{display:flex;height:100vh}.sidebar{width:240px;background:#f8fafc;padding:16px;display:flex;flex-direction:column;justify-content:space-between}.app-main{flex:1;display:flex;flex-direction:column}.navbar{height:64px;padding:0 20px;display:flex;justify-content:space-between;align-items:center;border-bottom:1px solid #e5e7eb}.app-content{padding:20px;background:#f1f5f9;flex:1}.card{background:#fff;padding:20px;border-radius:16px}.bg-layout{display:flex;gap:20px}.bg-list{display:flex;flex-direction:column;gap:12px}.bg-thumb{width:200px;border-radius:12px;cursor:pointer}.bg-thumb.active{outline:2px solid black}.bg-preview{flex:1;border:2px dashed #cbd5e1;border-radius:16px;display:flex;align-items:center;justify-content:center}.upload-layout{display:flex;gap:20px}.image-grid{display:grid;grid-template-columns:repeat(auto-fill,120px);gap:12px}.summary{width:300px}.bg-summary{height:120px;background-size:cover;border-radius:12px}@media(max-width:768px){.app-shell{flex-direction:column}.sidebar{display:none}.bg-layout,.upload-layout{flex-direction:column}.bg-list{flex-direction:row;overflow-x:auto}.summary{width:100%}}