A slide-in notification has both a delay before it starts and needs to stay in its final position once it finishes, so which single fill-mode value covers both requirements at once?

A developer applies will-change: transform to a button inside its :hover rule, intending to prepare it for an animation that only plays on click, so why is that timing a poor fit?

An animation repeatedly changes an element’s left and width values every frame to create a resizing, sliding effect, so what does that force the browser to redo on every single frame?

A blockquote component uses ::before with content: “\201C” to draw a large decorative opening quotation mark, so why is a Unicode escape used instead of just typing a literal quote character into the content string?

Before ::marker existed, a developer wanting colored bullet points different from the list item’s own text color had to resort to workarounds, so what does ::marker change about that?

Before ::first-letter existed, a developer wanting a classic drop-cap effect had to manually wrap the first letter of each paragraph in its own in the HTML, so what does ::first-letter change about that workflow?

A visitor has turned on their operating system’s Reduce Motion setting because on-screen movement makes them physically dizzy, so how does that OS-level preference reach the site’s CSS?

A loading spinner on a checkout page needs to rotate continuously for as long as the page is processing, so which limitation rules out using a transition for this effect?

An animation has a total duration of 3 seconds, so what happens if animation-delay is set to -5s, a magnitude larger than the animation’s own duration?

A developer sets animation-direction: reverse on a slide-in animation whose keyframes move an element from off-screen (0%) to its resting position (100%), so what will the element actually do?