.ontubs-app-surface {
    position: fixed;
    z-index: 0;
    inset: 0;
    isolation: isolate;
    width: 100%;
    height: 100dvh;
    overflow: hidden;
    color: #172033;
    background: #f3f7fc;
    font-family: system-ui, -apple-system, "Segoe UI", Roboto, Arial, sans-serif;
    line-height: normal;
}

.ontubs-site-surface {
    position: relative;
    z-index: 1;
    min-height: 100vh;
    opacity: 1;
    transition: opacity 150ms ease-out;
    will-change: opacity;
}

html[data-ontubs-surface="app"] { overflow: hidden; }
html[data-ontubs-surface="app"] .ontubs-site-surface { opacity: 0; pointer-events: none; }
html[data-ontubs-app-overlay] { overflow: hidden; }

.ontubs-app-surface[data-ontubs-surface="overlay"] {
    z-index: 2;
    background: transparent;
}

.ontubs-app-surface[data-ontubs-surface="overlay"] .application-shell > .titlebar,
.ontubs-app-surface[data-ontubs-surface="overlay"] .application-shell > main {
    visibility: hidden;
}

.ontubs-app-surface[data-ontubs-surface="overlay"] .application-shell > .application-modal-layer {
    visibility: visible;
}

@media (prefers-reduced-motion: reduce) {
    .ontubs-site-surface { transition-duration: 0s; }
}