Less not working in my widget

Hello,

my LESS not working and I don’t know why.

I’ve this in my main widget PHP file.

function get_style_name($instance) {
        return 'styles';
    }

This is my LESS file.

/*
Name: Style
Template: text-image-template
Author: Alex
*/
@background_color: #ffffff;
@border_radius: 5px;
.dmd-ti-container {
  background-color: @background_color;
  border-radius: @border_radius;
}

Is there something wrong?