<form>
  <label for="eposta">E-posta</label>
  <input type="email" required name="eposta" autocomplete="off" />
  <br /><br />
  <label for="password">Password</label>
  <input type="password" name="username" />
</form>
@import url("https://fonts.googleapis.com/css2?family=Viaoda+Libre&display=swap");

:root {
  --primary-color: #1f2029;
  --secondary-color: #2a2b38;
  --text-color: #c4c3ca;
  --form-bg-color: #2a2b38;
  --focus-bg-color: hsl(200deg, 55%, 92%);
  --white: #fff;
}

body {
  font-family: "Lato", sans-serif;
  display: flex;
  min-height: 100vh;
  justify-content: center;
  align-items: center;
  background-color: var(--primary-color);
  box-sizing: border-box;
}

form {
  background-color: var(--form-bg-color);
  border-radius: 6px;
  padding: 50px 50px 50px 25px;
  color: var(--text-color);
  width: 240px;
}

form:focus-within {
  position: relative;
}

form:focus-within:after {
  content: '';
  width: 300px;
  height: 95%;
  position: absolute;
  top: 10px;
  left: 10px;
  box-shadow: inset 0 0 60px whitesmoke, inset 20px 0 80px #f0f,
    inset -20px 0 80px #0ff, inset 20px 0 300px #f0f, inset -20px 0 300px #0ff,
    0 0 50px #fff, -10px 0 80px #f0f, 10px 0 80px #0ff;
  border-radius: 3px;
  z-index: -1;
}

label {
  font-size: 16px;
}

input {
  color: var(--white);
  background-color: var(--primary-color);
  border: 0;
  margin-top: 10px;
  padding: 12px;
  border-radius: 4px;
  font-size: 16px;
  outline: none;
  width: 100%;
}

input:focus {
  box-shadow: 0 1px 0 0 rgb(0 255 255 / 25%), 0 -1px 0 0 rgb(255 0 255 / 25%), 1px 0 0 0 rgb(0 255 255 / 25%), -1px 0 0 0 rgb(255 0 255 / 25%), 1px -1px 0 0 rgb(255 0 255 / 50%), -1px 1px 0 0 rgb(255 0 255 / 50%), 1px 1px 0 0 rgb(255 0 255 / 75%), -1px -1px 0 0 rgb(255 0 255 / 75%);
}

label:has(+ input:invalid)::before {
  content: '✖ ';
  color: #ff0024;
}

form:has(input:invalid)::after {
  box-shadow: inset 0 0 60px whitesmoke, inset 20px 0 80px #ff0024, inset -20px 0 80px #ff8f00, inset 20px 0 300px #ff0058, inset -20px 0 300px #ffc200, 0 0 50px #fff, -10px 0 80px #ff004a, 10px 0 80px #ff5b00;
}

External CSS

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External JavaScript

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