$trans-opacity__time: 0.3s;
$trans-opacity__function: ease-in;
$trans-opacity: $trans-opacity__time $trans-opacity__function;
convenience variable for using both$trans-move__time: 0.3s;
$trans-move__function: ease-in;
$trans-move: $trans-opacity__time $trans-move__function;
convenience variable for using both