Examples
 z-3 
 z-2 
 z-1 
 z-0 
 z-n1 
vue
<template>
 <b-div
  z="3"
  position="absolute"
  padding="5"
  rounded="3"
 >
  <b-span position="absolute">
   z-3
  </b-span>
 </b-div>
 <b-div
  z="2"
  position="absolute"
  padding="5"
  rounded="3"
 >
  <b-span position="absolute">
   z-2
  </b-span>
 </b-div>
 <b-div
  z="1"
  position="absolute"
  padding="5"
  rounded="3"
 >
  <b-span position="absolute">
   z-1
  </b-span>
 </b-div>
 <b-div
  z="0"
  position="absolute"
  padding="5"
  rounded="3"
 >
  <b-span position="absolute">
   z-0
  </b-span>
 </b-div>
 <b-div
  z="n1"
  position="absolute"
  padding="5"
  rounded="3"
 >
  <b-span position="absolute">
   z-n1
  </b-span>
 </b-div>
</template>