my.css

.input {
  position: relative;
  font-size: 1.5em;
  background: linear-gradient(21deg, #10abff, #1beabd);
  padding: 3px;
  display: inline-block;
  border-radius: 9999em;
}
.input *:not(span) {
  position: relative;
  display: inherit;
  border-radius: inherit;
  margin: 0;
  border: none;
  outline: none;
  padding: 0 0.325em;
  z-index: 1;
}
.input *:not(span):focus + span {
  opacity: 1;
  transform: scale(1);
}
.input span {
  transform: scale(0.993, 0.94);
  transition: transform 0.5s, opacity 0.25s;
  opacity: 0;
  position: absolute;
  z-index: 0;
  margin: 4px;
  left: 0;
  top: 0;
  right: 0;
  bottom: 0;
  border-radius: inherit;
  pointer-events: none;
  box-shadow: inset 0 0 0 3px #fff, 0 0 0 4px #fff, 3px -3px 30px #1beabd, -3px 3px 30px #10abff;
}

html {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif, "Apple Color Emoji", "Segoe UI Emoji", "Segoe UI Symbol";
  line-height: 1.5;
  font-size: 1em;
}



html, body {
  height: 100%;
}

input {
  font-family: inherit;
  line-height: inherit;
  color: #2e3750;
  min-width: 24em;
}

::-moz-placeholder {
  color: #cbd0d5;
}

:-ms-input-placeholder {
  color: #cbd0d5;
}

::placeholder {
  color: #cbd0d5;
  font-size: 20px;
}

html::after {
  content: "";
  background: linear-gradient(21deg, #10abff, #1beabd);
  height: 3px;
  width: 100%;
  position: absolute;
  left: 0;
  top: 0;
}