<button class="btn-98">Button</button>

.btn-98,
.btn-98 *,
.btn-98 :after,
.btn-98 :before,
.btn-98:after,
.btn-98:before {
  border: 0 solid;
  box-sizing: border-box;
}
.btn-98 {
  -webkit-tap-highlight-color: transparent;
  -webkit-appearance: button;
  background-color: #000;
  background-image: none;
  color: #fff;
  cursor: pointer;
  font-family: ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont,
    Segoe UI, Roboto, Helvetica Neue, Arial, Noto Sans, sans-serif,
    Apple Color Emoji, Segoe UI Emoji, Segoe UI Symbol, Noto Color Emoji;
  font-size: 100%;
  line-height: 1.5;
  margin: 0;
  -webkit-mask-image: -webkit-radial-gradient(#000, #fff);
  padding: 0;
}
.btn-98:disabled {
  cursor: default;
}
.btn-98:-moz-focusring {
  outline: auto;
}
.btn-98 svg {
  display: block;
  vertical-align: middle;
}
.btn-98 [hidden] {
  display: none;
}
.btn-98 {
  --thickness: 4px;
  background: none;
  box-sizing: border-box;
  -webkit-clip-path: polygon(
    0 0,
    100% 0,
    100% calc(100% + var(--thickness)),
    0 calc(100% + var(--thickness))
  );
  clip-path: polygon(
    0 0,
    100% 0,
    100% calc(100% + var(--thickness)),
    0 calc(100% + var(--thickness))
  );
  display: block;
  font-weight: 900;
  -webkit-mask-image: none;
  padding: 2px 0;
  position: relative;
  text-transform: uppercase;
}
.btn-98:before {
  background: #fff;
  bottom: calc(var(--thickness) * -1);
  content: "";
  display: block;
  height: var(--thickness);
  left: 0;
  pointer-events: none;
  position: absolute;
  width: 100%;
}
.btn-98:hover:before {
  -webkit-animation: slide 0.5s ease;
  animation: slide 0.5s ease;
}
@-webkit-keyframes slide {
  0% {
    transform: translateX(0);
  }
  50% {
    transform: translateX(100%);
  }
  51% {
    transform: translateX(-100%);
  }
  to {
    transform: translateX(0);
  }
}
@keyframes slide {
  0% {
    transform: translateX(0);
  }
  50% {
    transform: translateX(100%);
  }
  51% {
    transform: translateX(-100%);
  }
  to {
    transform: translateX(0);
  }
}