Pixel and rem sizes in variables

[quintus-luis]

pixel and rem sizes should be in variables:

For example:

$MAX_CONTENT_WIDTH: 600px

-> The boxes can be used everywhere. But by allowing only certain "distance categories", this creates a uniform look
$BOX_XXS: 0.25rem; //4px
$BOX_XS: 0.5rem; //8px
$BOX_S: 0.75rem; //12px
$BOX_M: 1rem; //16px
$BOX_L: 1.5rem; //24px
$BOX_XL: 2rem; //32px
$BOX_XXL: 2.5rem; //40px
$BOX_XXXL: 3.5rem; //56px
$BOX_XXXXL: 5rem; //80px

$BORDERRADIUS_S: 4px;
$BORDERRADIUS_M: 8px;
$BORDERRADIUS_L: 16px;