// Core variables and mixins
@import "variables.less";
@import "mixins/index.less";
// Core and Grid
@import "gantry-core.less";
@import "wordpress-core.less";
// Template core styling and layout
@import "template.less";
@import "style.less";
@import @headerstyle;
@import "prettify.less";

// Custom Overrides
@import "template-custom.less";

    $gantry->addLess('template-custom.less', myOverrides.css', 1000);

@import "jui/less/variables.less";      // Bootstrap style variables (to get the vars and their values used below)
@import "jui/less/mixins.less";         // Bootstrap Mixins

.btn {
    .buttonBackground(@btnPrimaryBackground, @btnPrimaryBackgroundHighlight);
}

    $this->addStyle($this->templateName . '-custom.css', 1000);

<div class="my-class-header">
    <h1>Header</h1>
</div>

@import "variables.less";   // For example, with over 20000 lines of variables
@import "mixin.less";      // For example, with over 50000 lines of mixins

// your override files
@import "your-custom.less";

@import "rockettheme/variables.less";   // rt_template variables
@import "rockettheme/mixin.less";      // rt_template mixins

@import "variables.less";   // For example, with over 20000 lines of variables
@import "mixin.less";      // For example, with over 50000 lines of mixins

@import "special-mixins-from-smashing-magazine.com.less";      // For example, with over 60000 lines of mixins

@import "myoverrides/your-custom-variables.less";   // For example, with over 5000 lines of different variables
@import "myoverrides/your-custom-mixin.less";      // For example, with over 10000 lines of mixins


// Colorize (for easieness here, but this is a part of a mixin file)
.doColorAnimation(@color, @animation) {
    .color: @color;
    .doAnimationFromSmashingMagazine(@animation);
}



// @header-dark is for example a variable thet is defined in your-custom-variables.less, and the animation (which is in this example a string/not a var) is in the smashing.mixin..less file with a simple ruleset like: if blingbling, then do this, if pulsate, do that
.my-class-header h1 {
    .doColorAnimation(@header-dark, blingbling);
}

.my-class-header h1 {
    color: black;
    -webkit-animation: ..........;
            animation: ..........;
    etc...   
}

@import "rt_template-variables.less";   // This file contain a variable => @headerColor: red;

// at this point the @headerColor is still "red"

@import "header-classes.less";   // This is for example a less file where RT defines all header classes, which need the var @headerColor

@import "rt_template-variables.less";   // This file contain a variable => @headerColor: red;

// at this point the @headerColor is still "red"

@import "my_override-variables.less";   // This file contain your variable as override => @headerColor: green;

// at this point the @headerColor now is "green"

@import "header-classes.less";   // This is for example a less file where RT defines all header classes, which need the var @headerColor