Anatomy of the App Showcase

A device mockup that looks convincing at every size usually means someone hand-tuned the notch and corner radius for 2–3 fixed breakpoints. AppShowcase doesn't have breakpoints — every radius, every inset, the notch itself, is a ratio of one width prop, computed once per render.

The whole frame is derived from one number

PhoneFrame reads a DEVICE table keyed by shellR, padR, and screenR — ratios, not pixels — and multiplies them by width to get every geometric value the frame needs:

const DEVICE = {
  iphone: { aspect: "aspect-[433/882]", shellR: 0.17, padR: 0.035, screenR: 0.13 },
  android: { aspect: "aspect-[9/19.5]", shellR: 0.11, padR: 0.028, screenR: 0.085 },
};

const geo = DEVICE[device];
const pad = w * geo.padR;
const shellRadius = w * geo.shellR;
const screenRadius = w * geo.screenR;
const notchW = w * 0.3;

Nothing here is a fixed rem value. Render the same AppShowcase at width={140} and width={400} and the shell radius, the padding gap, and the notch all scale together — a hand-picked radius would look chunky at 140 and hairline at 400. The Android variant is a second row in the same table (shellR: 0.11, hole-punch instead of a notch), not a fork of the component.

One SPRING, two motion sources

scroll mode — the default — runs Framer twice off the same config, for two unrelated things:

const SPRING = { stiffness: 320, damping: 32, mass: 0.9 };

// 1. Entrance — fires once, on scroll-into-view
<motion.div
  initial={{ opacity: 0, y: 48, rotateX: 10 }}
  whileInView={{ opacity: 1, y: 0, rotateX: 0 }}
  viewport={{ once: true, amount: 0.3 }}
  transition={{ type: "spring", ...SPRING }}
  className="[transform-style:preserve-3d] [perspective:1200px]"
/>

// 2. Scroll pan — tracks scroll position continuously
const { scrollYProgress } = useScroll({ target: sectionRef, offset: ["start end", "end start"] });
const y = useSpring(useTransform(scrollYProgress, [0, 1], ["0%", "-45%"]), SPRING);

The entrance is a one-shot spring gated by viewport={{ once: true }} — it plays exactly once and never re-triggers on re-scroll. The pan is the opposite: scrollYProgress recomputes every scroll tick, and wrapping it in useSpring smooths that raw, sometimes-jumpy scroll value into something that eases rather than jitters — the same physics config reused for a completely different job. rotateX: 10 → 0 on the entrance, combined with [perspective:1200px] on the wrapper, is what gives the phone a slight "tilting up out of the page" feel rather than a flat slide-up.

loop mode skips Framer entirely

<div
  className={`flex flex-col ${running ? "animate-app-showcase-scroll" : ""} motion-reduce:animate-none`}
  style={{ willChange: "transform", ["--as-loop"]: `${interval * 6}s` }}
>
  <img src={src} className="w-full" />
  {/* Duplicate for a seamless wrap. */}
  <img src={src} aria-hidden className="w-full" />
</div>

@keyframes app-showcase-scroll {
  from { transform: translateY(0); }
  to   { transform: translateY(-50%); }
}

Two identical copies of the screenshot stacked in a track exactly twice the image's height. Sliding that track up by -50% moves exactly one copy's height — so the instant the animation loops back to 0%, the pixels on screen are identical to the frame before the loop, and the seam is invisible. running gates the class with plain boolean logic (autoplay && inView && !reduce && !videoSrc) rather than a useAnimationFrame loop — once the class is attached, the browser's compositor drives every frame with zero React re-renders and zero Framer Motion overhead.

Idle when it can't be seen

const io = new IntersectionObserver(
  ([entry]) => setInView(entry.isIntersecting),
  { threshold: 0.2 },
);

inView folds into running alongside autoplay and reduce — scroll a showcase off-screen and its class drops, the CSS animation pauses, and the compositor has nothing left to do for that element. No requestAnimationFrame loop to cancel, because there never was one.

Reduced motion, mode by mode

Every mode reads useReducedMotion() once at the top of AppShowcase and threads a single reduce boolean down, but each mode answers it differently: scroll renders the static assembled frame with no entrance and no pan; loop's running check folds !reduce directly into whether the class is attached at all, and motion-reduce:animate-none backs that up at the CSS layer in case JS hasn't hydrated yet; carousel drops its AnimatePresence transition duration to 0; cluster skips wiring the pointer-parallax spring altogether. Four different mechanisms, one shared boolean, no mode left animating for a user who asked it to stop.

The result

Resultthe real component — auto-scrolling while in view

One ratio table building the whole shell, one shared spring config doing two unrelated jobs in scroll mode, and a loop mode that hands the browser's compositor a two-copy track and gets out of the way entirely.