body, html { margin: 0; padding: 0; height: 100%; overflow: hidden; }
#header { font-size: 13px; height: 100vh; position: relative; }
#mainFrame { width: 100%; height: 100%; position: fixed; top: 0; right: 0; bottom: 0; left: 0; z-index: 999999999999; border: none; background: #fff; }
#preloader { position: fixed; top: 0; left: 0; width: 100%; height: 100%; background: #fff; z-index: 9999999999999; display: flex; justify-content: center; align-items: center; transition: opacity 0.3s, visibility 0.3s; }
#preloader.hidden { opacity: 0; visibility: hidden; }
.spinner { width: 40px; height: 40px; border: 4px solid rgba(0,0,0,0.1); border-left-color: #000; border-radius: 50%; animation: spin 1s linear infinite; }
@keyframes spin { to { transform: rotate(360deg); } }