#flash-overlay { transition: opacity 0.5s ease-out; }

/* Hide the native disclosure triangle on the mobile-menu <summary>. */
.nav-summary { list-style: none; }
.nav-summary::-webkit-details-marker { display: none; }

/* Prevent the page from scrolling horizontally if any child overshoots
   on a narrow viewport. */
html, body { overflow-x: hidden; }