Given the following CSS applied to a single <div>: div { animation-name: spin; animation-duration: calc(infinity * 1s); } @keyframes spin { from { transform: translateX(0); } to { transform: translateX(100px); } } …the page is rendered, but becomes effectively unresponsive. • The browser window can be dragged around the screen, and closed with either mouse or keyboard commands, without apparent lag. • The page can be scrolled without apparent lag if the content is tall enough to trigger a scrollbar, but the layout is frozen at its initial paint state. • Resizing the browser window will leave the vertical scrollbar in its initial spot, even if the window is made wider or narrower. • If not already open at page load, the only way to open the Web Inspector is via the Develop menu. Once it is open, the Elements tab will either be incomplete or completely empty. • Contextual menus do not appear, and interactions (including drag-selection of page text) are ignored; indeed, the mouse cursor does not change from a pointer to an I-bar when hovering over text content. • Some attempts to interact with the browser viewport trigger a brief SBBoD, but more often have no visible effect. Firefox and Chrome will both render the above while remaining fully responsive. They do not, of course, show any visible animation, given that the time to complete it would be somewhere around ten times longer than the time at which almost all matter in the universe will have been swallowed by supermassive black holes, or else half again as long as the highest estimate of the time it will take for all nucleons in the observable universe to decay. (Source: Wikipedia’s “Timeline of the far future” page.)