как изминит opacitiy HTML елемента как гридиент чтоби растворить половину

.left-to-right {
  mask-image: linear-gradient(to left, rgba(0,0,0,0), rgba(0,0,0,1));
  -webkit-mask-image: linear-gradient(to left, rgba(0,0,0,0), rgba(0,0,0,1));
}

.rigth-to-left {
  mask-image: linear-gradient(to right, rgba(0,0,0,0), rgba(0,0,0,1));
  -webkit-mask-image: linear-gradient(to right, rgba(0,0,0,0), rgba(0,0,0,1));
}

.top-to-bottom {
  mask-image: linear-gradient(to bottom, rgba(0,0,0,0), rgba(0,0,0,1));
  -webkit-mask-image: linear-gradient(to bottom, rgba(0,0,0,0), rgba(0,0,0,1));
}

.bottom-to-top {
  mask-image: linear-gradient(to top, rgba(0,0,0,0), rgba(0,0,0,1));
  -webkit-mask-image: linear-gradient(to top, rgba(0,0,0,0), rgba(0,0,0,1));
}

.to-rottom-left {
  mask-image: linear-gradient(to left, rgba(0,0,0,0), rgba(0,0,0,1));
  -webkit-mask-image: linear-gradient(to bottom left, rgba(0,0,0,0), rgba(0,0,0,1));
}

.abrupt {
  mask-image: linear-gradient(to bottom left, 50% rgba(0,0,0,0), 50% rgba(0,0,0,1));
  -webkit-mask-image: linear-gradient(to bottom left, rgba(0,0,0,0) 50% ,rgba(0,0,0,1) 50%);
}

.round {
  mask-image: radial-gradient(rgba(0,0,0,0), rgba(0,0,0,1));
  -webkit-mask-image: radial-gradient(rgba(0,0,0,1) 50%, rgba(0,0,0,0) 60%);
}

/* ------------- card styles --------------*/

:root {
  --side: 100px;
  --inner-side: 90px;
}

body {
  background-color: #69c;

  counter-reset: section;
  display: flex;
  flex-wrap: wrap;
}

.character-box {
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  width: var(--side);
  height: var(--side);
  margin: 10px;
  line-height: var(--side);
  text-align: center;
  vertical-align: middle;
  position: relative;
  font-size: calc(var(--inner-side) / 1.5);
  font-family: Roboto, sans-serif;
  background-image: url(https://picsum.photos/id/12/400?blur=1.2);
}

.character-box::before {
  content: "";
  display: block;
  position: absolute;
  top: 0;
  width: 100%;
  height: 100%;
  background-image: url(https://picsum.photos/id/12/400?blur=1.2);
  z-index: -2;
}

.character-box::after {
  content: "";
  position: absolute;
  width: var(--inner-side);
  height: var(--inner-side);
  left: 50%;
  top: 50%;
  transform: translate(-50%, -50%);
  display: block;
  background-color: #111;
  z-index: -2;
}

<div class="left-to-right">
  <h2 class="character-box">A</h2>
</div>

<div class="rigth-to-left">
  <h2 class="character-box">A</h2>
</div>

<div class="top-to-bottom">
  <h2 class="character-box">A</h2>
</div>

<div class="bottom-to-top">
  <h2 class="character-box">A</h2>
</div>

<div class="abrupt">
  <h2 class="character-box">A</h2>
</div>

<div class="to-rottom-left">
  <h2 class="character-box">A</h2>
</div>

<div class="round">
  <h2 class="character-box">A</h2>
</div>