metamask-extension/ui/components/component-library/button-base/button-base.scss

.mm-button {
  position: relative;
  height: 40px;
  padding: 0;
  border-radius: 999px;
  cursor: pointer;
  color: var(--color-text-default);
  background-color: var(--brand-colors-grey-grey100);
  vertical-align: middle;
  user-select: none;

  &:active,
  &:hover {
    color: var(--color-text-default);
  }

  &--block {
    display: block;
    width: 100%;
  }

  &__content {
    height: 100%;
  }


  &--size-sm {
    height: 32px;
  }

  &--size-md {
    height: 40px;
  }

  &--size-lg {
    height: 48px;
  }

  &--size-auto {
    height: auto;
    background-color: transparent;
    border-radius: 0;
    vertical-align: top;
    font-family: inherit;
    font-weight: inherit;
    font-size: inherit;
    line-height: inherit;
    letter-spacing: inherit;
  }

  &--loading {
    cursor: not-allowed;
  }

  &--loading &__content {
    color: transparent;
  }

  &--disabled,
  &:disabled {
    opacity: 0.3;
    cursor: not-allowed;
  }

  &__icon-loading {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    animation: spinner 1.2s linear infinite;
  }
}



@keyframes spinner {
  to { transform: translate(-50%, -50%) rotate(360deg); }
}