Variables for item-width and item-height in collection-repeat?

    <div class='game'
         collection-repeat='game in games'
         item-width='{{ itemDimensions }}'
         item-height='{{ itemDimensions }}'
         style='padding:8px; border-style: none !important'> ... </div>

In controller:
$scope.itemDimensions = '105px'

I do this because I need to set the width and height through media queries in the controller.

Why does this not work, and how do you get around it?