#funFactContainer { opacity: 1; /* Ensure it is fully visible initially */ transition: opacity 200ms; /* Smooth transition for opacity changes */ } /* Initial state of the header */ #header { position: fixed; bottom: -100px; /* Start off-screen */ left: 0; width: 100%; /* Full width of the viewport */ transition: bottom 100ms; /* Smooth transition for bottom property */ opacity: 0; /* Ensure it's hidden initially */ } /* Animated state of the header */ #header.slide-in { bottom: 0; /* Slide into view */ opacity: 1; /* Make it visible */ }