// Tools :: Z-Index

// Function
@function z($layer) {
  @if not map-has-key($z-layers, $layer) {
    @warn "No layer found for `#{$layer}` in $z-layers map. Property ommitted.";
  }
  @return map-get($z-layers, $layer);
}

// Map
$z-layers: (
  'heaven': 5001,
  'modal': 3,
  'sticky': 2,
  'default': 1,
  'underground': -1,
  'hell': -5001,
);

// eg .modal { z-index: z("modal"); }  returns z-index: 3;