Let me start by showing you how I would do this in SCSS:
$submenu-padding-left: 1.5em;
transform: translateX(calc(-#{$submenu-padding-left} + .5em));
which would compile to:
transform: translateX(calc(-1.5em - .5em))
Basically SCSS allows me to concatenate a minus symbol -
with a variable in order to convert it to a negative value.
Is it possible to achieve this with CSS Variables?
Yes you can do it. Simply multiply by -1
:
:root {
--margin: 50px;
}
body {
margin: 0 100px;
border:1px solid;
}
.box-1 {
background: red;
height: 100px;
width: 200px;
margin-left: calc(-1 * var(--margin));
}
.box-2 {
background: green;
height: 100px;
width: 200px;
margin-left: calc(-1 * (-1 * var(--margin))); /* You can also nest calculation */
}
<div class="box-1">
</div>
<div class="box-2">
</div>