Generated by SassMeister.com.

SassMeister-input.sass

// ----
// libsass (v2.0.0)
// ----

/* =Mixin for dynamic backgrounds 
   =Author: @Donuteeze w/Adam Šír
   ============================== */

@mixin content-section-background($class, $nth-child:'all', $steps: 4 ) {
    @for $i from 1 through $steps {
        @if($nth-child == 'all') {
          &.#{$class}-#{$i} {
                background: url('../i/#{$class}-#{$i}.jpg') top center;
                background-repeat: no-repeat;
                background-size: cover;
          }
        }
        
        @if($nth-child == 'even') {
            @if($i % 2 ==0) {
                &.#{$class}-#{$i} {
                    background: url('../i/#{$class}-#{$i}.jpg') top center;
                    background-repeat: no-repeat;
                    background-size: cover;
                }
            }
        }
        
        @if($nth-child == 'odd') {
            @if($i % 2 != 0) {
              &.#{$class}-#{$i} {
                  background: url('../i/#{$class}-#{$i}.jpg') top center;
                  background-repeat: no-repeat;
                  background-size: cover;
              }
            }
        }
    }
}

// Examples
@include content-section-background('homepage', 'odd');
@include content-section-background('content-section-learn-item', 'even');
@include content-section-background('footer-item');

SassMeister-output.css

/* =Mixin for dynamic backgrounds 
   =Author: @Donuteeze w/Adam Šír
   ============================== */
.homepage-1 {
  background: url('../i/homepage-1.jpg') top center;
  background-repeat: no-repeat;
  background-size: cover; }

.homepage-3 {
  background: url('../i/homepage-3.jpg') top center;
  background-repeat: no-repeat;
  background-size: cover; }

.content-section-learn-item-2 {
  background: url('../i/content-section-learn-item-2.jpg') top center;
  background-repeat: no-repeat;
  background-size: cover; }

.content-section-learn-item-4 {
  background: url('../i/content-section-learn-item-4.jpg') top center;
  background-repeat: no-repeat;
  background-size: cover; }

.footer-item-1 {
  background: url('../i/footer-item-1.jpg') top center;
  background-repeat: no-repeat;
  background-size: cover; }

.footer-item-2 {
  background: url('../i/footer-item-2.jpg') top center;
  background-repeat: no-repeat;
  background-size: cover; }

.footer-item-3 {
  background: url('../i/footer-item-3.jpg') top center;
  background-repeat: no-repeat;
  background-size: cover; }

.footer-item-4 {
  background: url('../i/footer-item-4.jpg') top center;
  background-repeat: no-repeat;
  background-size: cover; }