Shelves using CraftML tags

index.xml

<craft>
    <info>
        <title>Bookshelf</title>
    </info>
    
    <style>
        * {color: brown;}
    </style>
    
    <param name="shelves" type="int" default="3"/>
    <param name="width" type="int" default="50"/>
    <param name="depth" type="int" default="15"/>
    <param name="thickness" type="int" default="2"/>
    <param name="back" type="int" default="1"/>
      
    <g l="centerX()">
        <!-- Back -->
        <script>
            if ($params.back)
            this.add('<cube size="{{width}} 1 {{(10 * shelves) + (thickness * (shelves + 1))}}"/>');
        </script>
           
        <g l="centerXY()">
            <!-- Sides -->
            <row spacing="{{width}}">
                <repeat n="2">
                    <cube size="{{thickness}} {{depth}} {{(10 * shelves) + (thickness * (shelves + 1))}}"/>
                </repeat>
            </row>
            
            <!-- Shelves -->
            <stack spacing="10">
                <repeat n="{{shelves + 1}}">
                    <cube size="{{width}} {{depth}} {{thickness}}"></cube>
                </repeat>
            </stack>
        </g>
    </g>

</craft>