WordPress/wp-includes/blocks/buttons/style.css

.wp-block-buttons.is-vertical{
  flex-direction:column;
}
.wp-block-buttons.is-vertical>.wp-block-button:last-child{
  margin-bottom:0;
}
.wp-block-buttons>.wp-block-button{
  display:inline-block;
  margin:0;
}
.wp-block-buttons.is-content-justification-left{
  justify-content:flex-start;
}
.wp-block-buttons.is-content-justification-left.is-vertical{
  align-items:flex-start;
}
.wp-block-buttons.is-content-justification-center{
  justify-content:center;
}
.wp-block-buttons.is-content-justification-center.is-vertical{
  align-items:center;
}
.wp-block-buttons.is-content-justification-right{
  justify-content:flex-end;
}
.wp-block-buttons.is-content-justification-right.is-vertical{
  align-items:flex-end;
}
.wp-block-buttons.is-content-justification-space-between{
  justify-content:space-between;
}
.wp-block-buttons.aligncenter{
  text-align:center;
}
.wp-block-buttons:not(.is-content-justification-space-between,.is-content-justification-right,.is-content-justification-left,.is-content-justification-center) .wp-block-button.aligncenter{
  margin-left:auto;
  margin-right:auto;
  width:100%;
}
.wp-block-buttons[style*=text-decoration] .wp-block-button,.wp-block-buttons[style*=text-decoration] .wp-block-button__link{
  text-decoration:inherit;
}
.wp-block-buttons.has-custom-font-size .wp-block-button__link{
  font-size:inherit;
}

.wp-block-button.aligncenter{
  text-align:center;
}