Liquid Metal Border

Core Contract

1. Use metal-fx in React 18 or newer.
2. Wrap exactly one real host element such as a button, a, div, or article.
3. Keep the host semantic and interactive. MetalFx is visual framing, not the control.
4. Reserve the animated border for active, selected, focused, hovered, or primary surfaces. Do not put it around every control.
5. Keep a static CSS border or focus outline as the fallback. WebGL decoration must never carry essential state by itself.
6. Pause non-active instances and reduced-motion experiences.
7. Test light and dark modes independently. Reflections intentionally render only in dark mode.

Inspect Before Editing

• Confirm the project uses React and has react and react-dom version 18 or newer.
• Find the real control, its dimensions, radius, background, border, outline, shadow, active-state source, and theme source.
• Decide whether the metal should be always visible or driven by active, selected, hover, or focus state.
• Check whether the project has a manual theme toggle. Use that state instead of theme="auto" when it does not follow the OS.
• Identify nearby elements that genuinely benefit from reflected light. Do not add reflections by default.
• Check the installed metal-fx version before relying on the prop surface below.

Install and Import

Install with the project's package manager:

npm install metal-fx
# pnpm add metal-fx
# yarn add metal-fx
# bun add metal-fx

Import the named React component:

import { MetalFx } from "metal-fx";

Do not import a stylesheet. The package injects its component styles. It supports ESM and CommonJS builds, is SSR-safe, and mounts the WebGL pipeline after hydration. In a Next.js App Router project, render it from a Client Component because the component uses client-side React hooks.

Baseline Button

Start with a restrained border before adding reflections or custom shader geometry:

import { MetalFx } from "metal-fx";

export function UpgradeButton() {
  return (
    <MetalFx
      variant="button"
      preset="chromatic"
      theme="auto"
      strength={0.85}
    >
      <button type="button">Upgrade to Pro</button>
    </MetalFx>
  );
}

The wrapper measures the child, paints the metal ring on top, and keeps the child interactive. Size the child normally with CSS, Tailwind, or inline styles.

Active-State Pattern

Keep one mounted instance and drive its intensity from real component state. Use aria-pressed, aria-selected, or the native selected-state mechanism so the visual effect is not the only signal.

"use client";

import { useEffect, useState } from "react";
import { MetalFx } from "metal-fx";

function useReducedMotion() {
  const [reduced, setReduced] = useState(false);

  useEffect(() => {
    const query = window.matchMedia("(prefers-reduced-motion: reduce)");
    const sync = () => setReduced(query.matches);

    sync();
    query.addEventListener("change", sync);
    return () => query.removeEventListener("change", sync);
  }, []);

  return reduced;
}

export function LiquidMetalToggle({
  selected,
  onSelect,
}: {
  selected: boolean;
  onSelect: () => void;
}) {
  const [hovered, setHovered] = useState(false);
  const [focused, setFocused] = useState(false);
  const reducedMotion = useReducedMotion();
  const highlighted = selected || hovered || focused;

  return (
    <MetalFx
      className="liquid-metal-toggle"
      variant="button"
      preset="chromatic"
      strength={highlighted ? 0.9 : 0.14}
      paused={reducedMotion || !highlighted}
      disableGlow={reducedMotion || !highlighted}
      ringCssPx={selected ? 1.5 : 1}
      normalizeHostStyles={false}
    >
      <button
        type="button"
        className="liquid-metal-toggle__control"
        aria-pressed={selected}
        onClick={onSelect}
        onPointerEnter={() => setHovered(true)}
        onPointerLeave={() => setHovered(false)}
        onFocus={() => setFocused(true)}
        onBlur={() => setFocused(false)}
      >
        Auto
      </button>
    </MetalFx>
  );
}

.liquid-metal-toggle {
  background: #18181b;
  border-radius: 999px;
}

.liquid-metal-toggle__control {
  min-height: 40px;
  padding: 0 18px;
  color: #fafafa;
  background: transparent;
  border: 0;
  border-radius: 999px;
  box-shadow: none;
}

.liquid-metal-toggle__control:focus-visible {
  outline: 2px solid #ffffff;
  outline-offset: 3px;
}

Use paused to stop non-active canvas updates; it freezes the last frame without hiding the ring. strength changes rendered opacity from 0 to 1 but does not slow the shader.

Static Border and Card Pattern

Use the wrapper as the surface when the child must remain transparent:

<MetalFx
  variant="button"
  preset="silver"
  theme="dark"
  strength={0.55}
  borderRadius={24}
  ringCssPx={1}
  shaderScale={1.45}
  disableGlow
  normalizeHostStyles={false}
  style={{ background: "#111318" }}
>
  <article className="feature-card">
    <h3>Realtime review</h3>
    <p>Keep feedback attached to the work.</p>
  </article>
</MetalFx>

Keep the article background transparent so it does not cover the ring. Use the child for content layout and the MetalFx wrapper for the visible surface.

Complete Customization Surface

Other valid HTMLDivElement attributes are forwarded to the wrapper.

Tuning Defaults

• Primary pill button: variant="button", strength={0.75}, ringCssPx={1}.
• Selected tab or filter: idle strength 0.1–0.2, selected strength 0.75–0.9.
• Icon button: variant="circle", explicit square child dimensions, strength={0.7}.
• Large card: ringCssPx={1}, shaderScale={1.3–1.6}, disableGlow.
• Premium CTA: start with chromatic; use silver for neutral UI and gold only for warm or luxury palettes.
• Quiet active state: disable glow before reducing the ring below legibility.
• Doubled design system: use scale={2} instead of independently doubling shader, ring, glow, and reflection values.

Keep strength <= 0.9 for routine controls. Full-strength chromatic metal can dominate labels and icons.

Sizing and Radius

Prefer sizing the child:

<MetalFx variant="circle">
  <button style={{ width: 36, height: 36 }} aria-label="Send">
    ↑
  </button>
</MetalFx>

To make the frame larger than the child, size the wrapper and stretch the child:

<MetalFx style={{ width: 44, height: 44 }} variant="circle">
  <button
    style={{ width: "100%", height: "100%" }}
    aria-label="Send"
  >
    ↑
  </button>
</MetalFx>

The wrapper uses display: inline-flex. Do not create cyclic percentage sizing where neither wrapper nor child has an intrinsic size.

Proximity Reflections

Pass only explicit refs to neighbouring elements:

import { useRef } from "react";

const chipRef = useRef<HTMLButtonElement>(null);

<>
  <button ref={chipRef}>Tools</button>
  <MetalFx variant="circle" reflectionTargets={[chipRef]}>
    <button aria-label="Send">↑</button>
  </MetalFx>
</>

Omit reflectionTargets to disable reflection work. In light mode, reflections are skipped automatically.

Accessibility and Motion

• Preserve native button, a, and form semantics inside the wrapper.
• Keep active state in aria-pressed, aria-selected, checked state, or current-route state.
• Do not rely on hue or animation alone. Retain text, icon, position, weight, or a static edge change.
• Be careful with normalizeHostStyles. Its default removes the child's outline; set it to false and define transparent chrome plus :focus-visible when the control needs its own focus ring.
• Set paused for reduced motion. Also disable the wandering glow when its movement is unnecessary.
• Keep the effect pointer-transparent and verify the child remains clickable and keyboard-operable.
• Retain a plain CSS border or surface treatment for WebGL failure.

Performance

metal-fx reuses one shared WebGL context, one compiled shader, and one animation loop across mounted instances. It also pauses offscreen copies with IntersectionObserver and debounces resize work through animation frames.

Still keep the effect selective:

• Mount it on primary or stateful surfaces, not whole grids of idle controls.
• Pause non-active instances.
• Omit reflections unless they add visible depth.
• Do not animate the wrapped element's dimensions continuously.
• Prefer disableGlow for restrained cards and dense toolbars.

Verification

Run the project's lint, typecheck, production build, tests, and git diff --check. Then verify in the Codex browser:

1. Confirm the package is present in the manifest and lockfile.
2. Confirm one .metal-fx-root wraps one semantic host.
3. Test hover, pointer-down, selected, keyboard focus, and disabled states.
4. Confirm the active state is exposed semantically and remains clear with the effect hidden.
5. Confirm the focus ring is visible when normalizeHostStyles is enabled or disabled.
6. Check the measured size and radius at every responsive breakpoint.
7. Test the app's real light and dark themes; do not assume auto matches a manual toggle.
8. Enable reduced motion and confirm the shader stops moving.
9. Scroll the control offscreen and back; confirm the effect resumes without a blank frame.
10. Check console output for WebGL, hydration, resize, or ref errors.
11. Confirm neighbouring controls receive reflections only when explicitly targeted in dark mode.

Failure Diagnosis

• The ring is covered: the child has an opaque background above the canvas. Use default normalization or make the child transparent and style the wrapper.
• The focus ring disappeared: normalizeHostStyles removed the child outline. Set it to false and reset only background, border, and shadow in project CSS.
• The radius is wrong: use a real computed radius on the child or pass borderRadius explicitly.
• A circle looks soft or thin: use variant="circle" and explicit square dimensions before increasing ringCssPx.
• The pattern is too busy: lower strength, disable glow, or use silver; do not immediately thicken the ring.
• Reflections are missing in light mode: expected behavior; reflections are dark-mode only.
• The effect is the wrong physical size after zooming: set scale to the UI scale instead of tuning each pixel constant independently.
• The page crashes in a server component: move the usage behind the framework's client-component boundary.
• The border is blank on unsupported hardware: keep the semantic control and CSS fallback complete; treat the WebGL ring as enhancement.

Handoff

Report the installed metal-fx version, wrapped control, active-state source, preset, theme strategy, fallback border, reduced-motion behavior, build/test results, and Codex-browser verification. Distinguish local readiness from a deployed result.