Generated by SassMeister.com.

SassMeister-input-HTML.html

<div class="derecha">leleder</div>
<div class="izquierda">leleizq</div>

SassMeister-input.scss

// ----
// Sass (v3.4.7)
// Compass (v1.0.1)
// ----

@mixin caja($ubi){ //ubi= ubicación
  float:$ubi;
  width: 48%;
  height: 100vh;
  margin: 1%;
}

.derecha{
  @include caja(right);
  $oscurecer: darken(#900, 20%);
  background: linear-gradient(#900, $oscurecer);
}

.izquierda{
  @include caja(left);
  $aclarar: lighten(#030, 40%);
  background: linear-gradient(#030, $aclarar);
}

SassMeister-output.css

.derecha {
  float: right;
  width: 48%;
  height: 100vh;
  margin: 1%;
  background: linear-gradient(#900, #330000);
}

.izquierda {
  float: left;
  width: 48%;
  height: 100vh;
  margin: 1%;
  background: linear-gradient(#030, lime);
}

SassMeister-rendered.html

<div class="derecha">leleder</div>
<div class="izquierda">leleizq</div>