body {
  display: flex;
  justify-content: center;
  align-items: center;
  min-height: 100vh;
}

.btn {
  margin: 1rem;
}
.btn-jittery {
  -webkit-animation: jittery 4s infinite;
          animation: jittery 4s infinite;
}
.btn-icon {
  position: relative;
  margin-left: 8px;
  overflow: hidden;
}
.btn-icon i {
  position: absolute;
  top: 41%;
  left: 48%;
  transform: scale(0.75) translate(-16%, 400%);
  transition: 0.2s;
}
.btn-icon span {
  display: flex;
  justify-content: center;
  align-items: center;
  transition: 0.2s;
}
.btn-icon:hover i {
  transform: scale(0.75) translate(-16%, 0);
}
.btn-icon:hover span {
  transform: translateY(-400%);
}
.btn-jelly:hover {
  -webkit-animation: jelly 0.5s;
          animation: jelly 0.5s;
}
.btn-fill {
  transition: 0.3s;
}
.btn-fill:hover {
  background: transparent;
  box-shadow: inset 0 0 0 36px var(--btn-bg);
}
.btn-open {
  transition: 0.3s;
}
.btn-open::before {
  position: absolute;
  content: "";
  top: 0;
  left: 0;
  z-index: -1;
  width: 100%;
  height: 100%;
  background: var(--btn-bg);
  transform: scaleX(0);
  transition: 0.3s;
}
.btn-open:hover {
  background: transparent;
}
.btn-open:hover::before {
  transform: scaleX(1);
}
.btn-pulse:hover {
  box-shadow: 0 0 0 18px transparent;
  -webkit-animation: pulse 1s;
          animation: pulse 1s;
}
.btn-close {
  transition: 0.3s;
}
.btn-close:hover {
  background: transparent;
  box-shadow: inset 54px 0 0 0 var(--btn-bg), inset -54px 0 0 0 var(--btn-bg);
}
.btn-slash {
  overflow: hidden;
  transition: 0.3s;
}
.btn-slash::before {
  position: absolute;
  content: "";
  top: 50%;
  left: 50%;
  z-index: -1;
  width: 120%;
  height: 210%;
  background: var(--btn-bg);
  transform: translate(-50%, -50%) rotate(-45deg) scaleX(0);
  transition: 0.3s;
}
.btn-slash:hover {
  background: transparent;
}
.btn-slash:hover::before {
  transform: translate(-50%, -50%) rotate(-45deg) scaleX(1);
}
.btn-fill-up {
  transition: 0.3s;
}
.btn-fill-up:hover {
  background: transparent;
  box-shadow: inset 0 -54px 0 0 var(--btn-bg);
}
.btn-slide {
  transition: 0.3s;
}
.btn-slide:hover {
  background: transparent;
  box-shadow: inset 90px 0 0 0 var(--btn-bg);
}
.btn-through {
  transition: 0.6s cubic-bezier(0.77, 0, 0.175, 1);
}
.btn-through::before {
  position: absolute;
  content: "";
  top: 0;
  left: 0;
  z-index: -1;
  width: 100%;
  height: 100%;
  background: var(--btn-bg);
  transform: scaleX(0);
  transform-origin: right;
  transition: transform 0.6s cubic-bezier(0.77, 0, 0.175, 1);
}
.btn-through:hover {
  color: white;
  background: transparent;
}
.btn-through:hover::before {
  transform: scaleX(1);
  transform-origin: left;
}
.btn-offset {
  border-radius: 0;
  box-shadow: 6px 6px 0 0 var(--btn-bg), inset 6px 6px 0 0 var(--btn-bg);
  transition: 0.3s;
}
.btn-offset:hover {
  background: transparent;
  box-shadow: 0 0 0 0 var(--btn-bg), inset 108px 72px 0 0 var(--btn-bg);
}
.btn-flip-down {
  --flip-button-height: 40px;
  height: var(--flip-button-height);
  color: transparent;
  border: none;
  border-radius: 0;
  perspective: 500px;
  transition: 0.3s;
}
.btn-flip-down:hover {
  color: transparent;
  background: transparent;
}
.btn-flip-down .front,
.btn-flip-down .back {
  position: absolute;
  top: 0;
  left: 0;
  display: flex;
  justify-content: center;
  align-items: center;
  width: 100%;
  height: 100%;
}
.btn-flip-down .front {
  background: var(--btn-bg);
  color: white;
  transition: 0.3s;
  transform-origin: center center calc(var(--flip-button-height) / -2);
}
.btn-flip-down .back {
  color: white;
  background: var(--btn-bg);
  transform: rotateX(88deg);
  transform-origin: center center calc(var(--flip-button-height) / -2);
  transition: 0.3s;
}
.btn-flip-down:hover .front {
  transform: rotateX(-90deg);
}
.btn-flip-down:hover .back {
  transform: rotateX(0deg);
}
.btn-marquee {
  font-weight: 600;
  border: none;
  overflow: hidden;
  transition: 0.3s;
}
.btn-marquee:hover {
  transform: scale(1.1);
}
.btn-marquee span {
  display: block;
  padding: 0 20px;
  -webkit-animation: move-left 2s linear infinite;
          animation: move-left 2s linear infinite;
}
.btn-marquee span::after {
  position: absolute;
  content: attr(data-text);
  top: 0;
  left: 100%;
  display: flex;
  justify-content: center;
  align-items: center;
  width: 100%;
  height: 100%;
}
.btn-cross {
  transform: rotate(0);
  overflow: hidden;
  transition: 0.3s;
}
.btn-cross::before, .btn-cross::after {
  position: absolute;
  content: "";
  left: 0;
  z-index: -1;
  width: 100%;
  height: 50%;
  background: var(--btn-bg);
  transform: scaleX(0);
  transition: transform 0.5s;
}
.btn-cross::before {
  top: 0;
  transform-origin: left;
}
.btn-cross::after {
  top: 50%;
  transform-origin: right;
}
.btn-cross:hover {
  background: transparent;
}
.btn-cross:hover::before, .btn-cross:hover::after {
  transform: scaleX(1);
}
.btn-cross:hover::before {
  transform-origin: right;
}
.btn-cross:hover::after {
  transform-origin: left;
}
.btn-open-line {
  border: none;
  transition: 0.3s;
}
.btn-open-line::before, .btn-open-line::after {
  position: absolute;
  content: "";
  left: 0;
  width: 100%;
  height: 1px;
  background: var(--btn-bg);
  opacity: 0;
  transform: scaleX(0);
  transition: 0.4s ease-in-out;
}
.btn-open-line::before {
  top: 0;
}
.btn-open-line::after {
  bottom: 0;
}
.btn-open-line:hover {
  letter-spacing: 5px;
  color: var(--btn-bg);
  background: transparent;
}
.btn-open-line:hover::before, .btn-open-line:hover::after {
  opacity: 1;
  transform: scaleX(1.2);
}

@-webkit-keyframes jittery {
  5%, 50% {
    transform: scale(1);
  }
  10% {
    transform: scale(0.9);
  }
  15% {
    transform: scale(1.15);
  }
  20% {
    transform: scale(1.15) rotate(-5deg);
  }
  25% {
    transform: scale(1.15) rotate(5deg);
  }
  30% {
    transform: scale(1.15) rotate(-3deg);
  }
  35% {
    transform: scale(1.15) rotate(2deg);
  }
  40% {
    transform: scale(1.15) rotate(0);
  }
}

@keyframes jittery {
  5%, 50% {
    transform: scale(1);
  }
  10% {
    transform: scale(0.9);
  }
  15% {
    transform: scale(1.15);
  }
  20% {
    transform: scale(1.15) rotate(-5deg);
  }
  25% {
    transform: scale(1.15) rotate(5deg);
  }
  30% {
    transform: scale(1.15) rotate(-3deg);
  }
  35% {
    transform: scale(1.15) rotate(2deg);
  }
  40% {
    transform: scale(1.15) rotate(0);
  }
}
@-webkit-keyframes jelly {
  25% {
    transform: scale(0.9, 1.1);
  }
  50% {
    transform: scale(1.1, 0.9);
  }
  75% {
    transform: scale(0.95, 1.05);
  }
}
@keyframes jelly {
  25% {
    transform: scale(0.9, 1.1);
  }
  50% {
    transform: scale(1.1, 0.9);
  }
  75% {
    transform: scale(0.95, 1.05);
  }
}
@-webkit-keyframes pulse {
  from {
    box-shadow: 0 0 0 0 var(--btn-bg);
  }
}
@keyframes pulse {
  from {
    box-shadow: 0 0 0 0 var(--btn-bg);
  }
}
@-webkit-keyframes move-left {
  to {
    transform: translateX(-100%);
  }
}
@keyframes move-left {
  to {
    transform: translateX(-100%);
  }
}