# Center-out underline input

> A single thin line under the text; on focus a gradient line opens out from the middle.

- Category: [Inputs](https://library.aimran.es/components/inputs)
- Built with: HTML + CSS
- Live editor: https://library.aimran.es/blocks/uv-in2-underline
- Library: AIMRAN Library (https://library.aimran.es), free, no sign-up, by Aimran Oukham

## Where to use it

No box, no background, just a line. That minimal look belongs on pages where the design does the talking: the contact form of a photographer’s portfolio, the newsletter field of an online magazine or an RSVP page for a wedding. The gradient line opening from the centre shows focus clearly. An underline input animation in CSS.

The resting line is very light, so check it on your real background; on pale colours you may need to darken it. It shines with two or three fields, less so on a long form where boxes are easier to scan.

## Code

### HTML

```html
<label class="uv-in2u"><input placeholder="Name"><i></i></label>
```

### CSS

```css
.uv-in2u {
  --c1: #0071e3;
  --c2: #8ec5ff;
  --s: 16px;
  /* tamaño */
  --k: 1;
  /* velocidad */
  --fg: #1d1d1f;
  /* texto */
  --bg: #f5f5f7;
  /* fondo */
}

.uv-in2u {
  font-family: -apple-system,BlinkMacSystemFont,"SF Pro Text","Inter",system-ui,sans-serif;
  font-size: var(--s);
  color: var(--fg);
  -webkit-tap-highlight-color: transparent;
  position: relative;
  display: block;
  width: 15em;
}

.uv-in2u input {
  font-family: -apple-system,BlinkMacSystemFont,"SF Pro Text","Inter",system-ui,sans-serif;
  width: 100%;
  box-sizing: border-box;
  padding: .75em .2em;
  font-size: var(--s);
  color: var(--fg);
  background: none;
  border: 0;
  outline: 0;
  box-shadow: inset 0 -1.5px 0 color-mix(in srgb,var(--fg) 16%,transparent);
}

.uv-in2u input::placeholder {
  color: color-mix(in srgb,var(--fg) 40%,transparent);
}

.uv-in2u i {
  position: absolute;
  left: 0;
  bottom: 0;
  width: 100%;
  height: 2px;
  border-radius: 2px;
  background: linear-gradient(90deg,var(--c2),var(--c1));
  scale: 0 1;
  transition: scale calc(0.4s / var(--k)) cubic-bezier(.25,.1,.25,1);
}

.uv-in2u input:focus ~ i {
  scale: 1 1;
}
```

### React

```tsx
import type { CSSProperties } from "react";

const css = `
.uv-in2u {
  font-family: -apple-system,BlinkMacSystemFont,"SF Pro Text","Inter",system-ui,sans-serif;
  font-size: var(--s);
  color: var(--fg);
  -webkit-tap-highlight-color: transparent;
  position: relative;
  display: block;
  width: 15em;
}

.uv-in2u input {
  font-family: -apple-system,BlinkMacSystemFont,"SF Pro Text","Inter",system-ui,sans-serif;
  width: 100%;
  box-sizing: border-box;
  padding: .75em .2em;
  font-size: var(--s);
  color: var(--fg);
  background: none;
  border: 0;
  outline: 0;
  box-shadow: inset 0 -1.5px 0 color-mix(in srgb,var(--fg) 16%,transparent);
}

.uv-in2u input::placeholder {
  color: color-mix(in srgb,var(--fg) 40%,transparent);
}

.uv-in2u i {
  position: absolute;
  left: 0;
  bottom: 0;
  width: 100%;
  height: 2px;
  border-radius: 2px;
  background: linear-gradient(90deg,var(--c2),var(--c1));
  scale: 0 1;
  transition: scale calc(0.4s / var(--k)) cubic-bezier(.25,.1,.25,1);
}

.uv-in2u input:focus ~ i {
  scale: 1 1;
}
`;

export default function In2Underline() {
  return (
    <>
      <style>{css}</style>
      <div
        style={{
          "--c1": "#0071e3",
          "--c2": "#8ec5ff",
          "--s": "16px",
          "--k": "1",
          "--fg": "#1d1d1f",
          "--bg": "#f5f5f7",
        } as CSSProperties}
      >
        <label className="uv-in2u"><input placeholder="Name" /><i></i></label>
      </div>
    </>
  );
}
```

## Prompt for AI assistants

Paste this into ChatGPT, Claude, Cursor, v0 or Lovable to adapt the block to your stack (Tailwind, Vue, Svelte…):

````text
I want to add the “Center-out underline input” block (Inputs) from AIMRAN Library to my project.

## What it is
A single thin line under the text; on focus a gradient line opens out from the middle.

## Chosen settings
- Main color: #0071e3
- Secondary color: #8ec5ff
- Size: 16px (from 12 to 24px)
- Speed: 1x (from 0.5 to 2x)
- Text: "Name"

## What I need
1. Add it to my project with the same look and animation as the reference code: same sizes, colours, radii, shadows, timings and easing.
2. It is built with plain HTML and CSS (the reference wraps it in a React component with its CSS). If my project uses something else (Vue, Svelte, Astro, plain HTML…), translate it without losing any behaviour. If I use Tailwind, turn the styles into classes; if not, keep the CSS in its own file.
3. Expose the settings above as props (or CSS variables) with those values as defaults.
4. Make it work well on phones: nothing that depends only on hover, touch targets of at least 44 px and no overflow on 320 px screens.
5. Make it look right in light and dark mode.
6. Keep it accessible: semantic HTML, roles and aria-* where needed, visible focus and keyboard support.
7. Respect prefers-reduced-motion: with reduced motion, no big animations but the same end result.

## Reference code
```tsx
import type { CSSProperties } from "react";

const css = `
.uv-in2u {
  font-family: -apple-system,BlinkMacSystemFont,"SF Pro Text","Inter",system-ui,sans-serif;
  font-size: var(--s);
  color: var(--fg);
  -webkit-tap-highlight-color: transparent;
  position: relative;
  display: block;
  width: 15em;
}

.uv-in2u input {
  font-family: -apple-system,BlinkMacSystemFont,"SF Pro Text","Inter",system-ui,sans-serif;
  width: 100%;
  box-sizing: border-box;
  padding: .75em .2em;
  font-size: var(--s);
  color: var(--fg);
  background: none;
  border: 0;
  outline: 0;
  box-shadow: inset 0 -1.5px 0 color-mix(in srgb,var(--fg) 16%,transparent);
}

.uv-in2u input::placeholder {
  color: color-mix(in srgb,var(--fg) 40%,transparent);
}

.uv-in2u i {
  position: absolute;
  left: 0;
  bottom: 0;
  width: 100%;
  height: 2px;
  border-radius: 2px;
  background: linear-gradient(90deg,var(--c2),var(--c1));
  scale: 0 1;
  transition: scale calc(0.4s / var(--k)) cubic-bezier(.25,.1,.25,1);
}

.uv-in2u input:focus ~ i {
  scale: 1 1;
}
`;

export default function In2Underline() {
  return (
    <>
      <style>{css}</style>
      <div
        style={{
          "--c1": "#0071e3",
          "--c2": "#8ec5ff",
          "--s": "16px",
          "--k": "1",
          "--fg": "#1d1d1f",
          "--bg": "#f5f5f7",
        } as CSSProperties}
      >
        <label className="uv-in2u"><input placeholder="Name" /><i></i></label>
      </div>
    </>
  );
}
```

Give me the complete final code, ready to paste, and tell me in one line where to put it in my project.
````