Shimmer Text

A text gradient moved behind the glyphs. The element gets `background-clip: text` and transparent text, and a `--shimmer-gradient` of five stops (muted, a color-mix shoulder, the tone's band colour, a shoulder, muted) with the bright band `spread`% wide. The background is 300% of the element's width, so the band starts and ends fully off the text and the loop restart is invisible. Motion animates `background-position` from `100% 0` to `0% 0`, eased in-out and repeating with a `pause` rest between sweeps. Reduced motion is handled in CSS (`motion-reduce:bg-none` plus the muted text color) rather than in JS, so server and client markup match and the text is readable before hydration.

**Pebble (2026-11-03).** Added `tone` and `pause`. `tone="ember"` paints the band with `--accent` for a live process (an agent running, a sync in flight) and is meant to be used sparingly; `ink` stays the default; the root carries `data-tone`. The gradient gained a soft shoulder on each side of the band (a 55% `color-mix` of band and muted at a quarter-spread from centre) so the band edges no longer read as a stripe. The sweep is now eased (`easeInOut`) with a `repeatDelay` of `pause` seconds, so it reads as light passing over the text rather than a conveyor belt. Reduced-motion handling is unchanged.

<!-- PEBBLE-LICENSE -->

registry/text/shimmer-text/shimmer-text.tsx

"use client";

/* PEBBLE-LICENSE
Built by Pebble. Component: shimmer-text.

First-party license: MIT

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END PEBBLE-LICENSE */

import * as React from "react";
import { motion } from "motion/react";

import { cn } from "@/lib/utils";

// Hydration-safe reduced motion: the server (and the hydration pass) render
// "no preference", then the real preference applies right after hydration.
const subscribeReduce = (onChange: () => void) => {
  const mq = window.matchMedia("(prefers-reduced-motion: reduce)");
  mq.addEventListener("change", onChange);
  return () => mq.removeEventListener("change", onChange);
};
const getReduce = () => window.matchMedia("(prefers-reduced-motion: reduce)").matches;
const useReduceMotion = () => React.useSyncExternalStore(subscribeReduce, getReduce, () => false);

const elements = {
  span: motion.span,
  p: motion.p,
  div: motion.div,
} as const;

// The band colour per tone. Ink is the default; ember marks a live process
// (an agent running, a sync in flight) and should be used sparingly.
const bands = {
  ink: "var(--foreground)",
  ember: "var(--accent)",
} as const;

export type ShimmerTextProps = Omit<
  React.ComponentProps<"span">,
  "children" | "style" | "onAnimationStart" | "onDrag" | "onDragStart" | "onDragEnd"
> & {
  as?: keyof typeof elements;
  /** Seconds per sweep. */
  duration?: number;
  /** Width of the band, as a percentage of the gradient (0–33). */
  spread?: number;
  /** Seconds of rest between sweeps. */
  pause?: number;
  /** Colour of the band of light: ink (default) or the ember accent. */
  tone?: keyof typeof bands;
  children: React.ReactNode;
  style?: React.CSSProperties;
};

export function ShimmerText({
  as = "span",
  duration = 2,
  spread = 20,
  pause = 0.4,
  tone = "ink",
  className,
  style,
  children,
  ...props
}: ShimmerTextProps) {
  const reduceMotion = useReduceMotion();
  // The three elements take the same props here; narrow to one for typing.
  const Comp = elements[as] as typeof motion.span;
  // Past 33% the band would already overlap the text on the first frame and
  // jump at each loop restart.
  const half = Math.min(Math.max(Number.isFinite(spread) ? spread : 20, 0), 33) / 2;
  const rest = Number.isFinite(pause) && pause > 0 ? pause : 0;
  const resolvedTone = Object.hasOwn(bands, tone) ? tone : "ink";
  const band = bands[resolvedTone];

  return (
    <Comp
      data-slot="shimmer-text"
      data-tone={resolvedTone}
      // Reduced motion is handled in CSS so server and client markup match:
      // the gradient is dropped and the text falls back to the muted colour.
      className={cn(
        as === "span" ? "inline-block" : "w-fit",
        "bg-[image:var(--shimmer-gradient)] bg-size-[300%_100%] bg-clip-text bg-no-repeat text-transparent",
        "motion-reduce:bg-none motion-reduce:text-muted-foreground",
        className,
      )}
      style={
        {
          // Three times the text width, so the band starts and ends fully off
          // the glyphs and the loop has no visible jump. A soft shoulder on
          // each side of the band keeps its edges from reading as a stripe.
          "--shimmer-gradient": `linear-gradient(90deg, var(--muted-foreground) ${50 - half}%, color-mix(in oklab, ${band} 55%, var(--muted-foreground)) ${50 - half / 2}%, ${band} 50%, color-mix(in oklab, ${band} 55%, var(--muted-foreground)) ${50 + half / 2}%, var(--muted-foreground) ${50 + half}%)`,
          backgroundPosition: "100% 0",
          ...style,
        } as React.CSSProperties
      }
      animate={reduceMotion ? undefined : { backgroundPosition: ["100% 0", "0% 0"] }}
      // Eased rather than linear, with a short rest between sweeps, so it
      // reads as light passing over the text rather than a conveyor belt.
      transition={{ duration, ease: "easeInOut", repeat: Infinity, repeatDelay: rest }}
      {...props}
    >
      {children}
    </Comp>
  );
}