<form>
      <div class="form-group">
        <label for="email" class="form-label">Email</label>
        <input required type="email" id="email" class="form-input" pattern="[a-z0-9._%+-][email protected][a-z0-9.-]+\.[a-z]{2,4}$" title="Enter valid email address" placeholder="Enter valid email address"/>   
      </div>
    </form>
*,
*:after,
*:before {
  box-sizing: border-box;
}

:root {
  --red: hsl(18 100% 50%);
  --green: hsl(130 52% 46%);
  --yellow: hsl(44 83% 53%);
  --blue: hsl(215 100% 53%);
  --grey: hsl(0 0% 45%);
  --text: var(--gray-5);
  --transition: 0.2s;
  --valid: var(--green);
  --invalid: var(--red);
  --focus: var(--violet-4);
  --blur: var(--indigo-4);
  --disabled: var(--grey);
}

:where(html) {
	color-scheme: none;
}

body {
  display: grid;
  min-height: 100vh;
  font-family: 'Google Sans', sans-serif, system-ui;
  place-items: center;
  overflow:  hidden;
  margin: 0;
  background-color: transparent;
  font-size: 1rem;
}

form {
  display: grid;
  grid-gap: 1rem;
}

input {
  border: 4px solid var(--color);
  border-radius: 4px;
  padding: 1rem 2rem;
  font-weight: 400;
  transition: border-color var(--transition);
}

input:focus-visible {
  outline-color: var(--color);
}

input::placeholder {
  color: transparent;
}

.form-group {
  display: flex;
  align-items: center;
  justify-content: flex-end;
}

label {
  font-family: sans-serif;
  display: flex;
  font-weight: bold;
  padding-right: 1rem;
  transform-style: preserve-3d;
  transition: color var(--transition);
  color: var(--color);
  font-size: 1.25rem;
}

.form-group:has(:invalid) {
  --color: var(--invalid);
}

.form-group:has(:focus) {
  --color: var(--focus);
}

.form-group:has(:valid) {
  --color: var(--valid);
}

.form-group:has(:placeholder-shown) {
  --color: var(--blur);
}

External CSS

  1. https://codepen.io/jh3y/pen/zYRjgjW.css
  2. https://unpkg.com/open-props/colors-hsl.min.css
  3. https://unpkg.com/open-props/open-props.min.css
  4. https://unpkg.com/open-props/normalize.min.css

External JavaScript

  1. https://codepen.io/jh3y/pen/zYRjgjW.js