style.css

* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

.container {
  height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  background: linear-gradient(#e66465, #9198e5);
  transition: background 0.2s ease;
}

.btn {
  width: 50%;
  position: relative;
  display: inline-block;
  padding: 10px 20px;
  text-transform: uppercase;
  border: 1px solid #ff6768;
  border-radius: 5px;
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, 'Open Sans', 'Helvetica Neue', sans-serif;
  font-size: 18px;
  color: #263859;
  background-color: #6b778d;
  cursor: pointer;
  overflow: hidden;
  transition: 0.3s;
}

.btn::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  width: 2em;
  height: 100%;
  background-color: rgba(255, 255, 255, 0.3);
  transform: translateX(-3.5em) skewX(-45deg);
}

.btn:hover {
  color: #6798f2;
  background-color: #3f4653;
}

.btn:active {
  transform: scale(105%);
}

.btn:hover:before {
  animation: moveLight 1s;
}

@keyframes moveLight {
  from {
    transform: translateX(-3.5em) skewX(-45deg);
  }
  to {
    transform: translateX(10em) skewX(-45deg);
  }
}

.block {
  position: relative;
  display: flex;
  flex-direction: column;
  align-items: center;
}

.text {
  width: 300px;
  display: inline-block;
  padding: 10px 28px;
  margin-bottom: 20px;
  border: 1px solid #17223b;
  border-radius: 5px;
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, 'Open Sans', 'Helvetica Neue', sans-serif;
  background-color: transparent;
  color: #fff;
  outline: transparent;
  box-shadow: 0 0 5px 1px #fff;
  transition: box-shadow 0.3s;
}

.text--active {
  box-shadow: 0 0 5px 1px rgb(80 229 57);
}

.copy_btn {
  position: absolute;
  top: 6px;
  right: 10px;
  height: 25px;
  width: 25px;
  padding: 0;
  border: none;
  font: inherit;
  color: inherit;
  background-color: transparent;
  cursor: pointer;
  outline-color: #ff6768;
}

.copy_mark {
  position: absolute;
  display: block;
  top: 7px;
  left: 7px;
  width: 20px;
  height: 20px;
  background-image: url('checkmark.svg');
  background-repeat: no-repeat;
  background-size: 12px;
  opacity: 0;
  transition: opacity 0.5s;
}

.copy_mark--active {
  opacity: 1;
}

.copy_svg {
  fill: rgb(80 229 57);
}