text: Polymer({
  
      is: 'paper-card',
  
      properties: {
  
        /**
         * The title of the card.
         */
        heading: {
          type: String,
          value: '',
          observer: '_headingChanged'
        },
  
        /**
         * The url of the title image of the card.
         */
        image: {
          type: String,
          value: ''
        },
  
        /**
         * The z-depth of the card, from 0-5.
         */
        elevation: {
          type: Number,
          value: 1
        },
  
        /**
         * Set this to true to animate the card shadow when setting a new
         * `z` value.
         */
        animatedShadow: {
          type: Boolean,
          value: false
        }
      },
  
      _headingChanged: function(heading) {
        var label = this.getAttribute('aria-label');
        this.setAttribute('aria-label', heading);
      },
  
      _computeHeadingClass: function(image) {
        var cls = 'title-text';
        if (image)
          cls += ' over-image';
        return cls;
      }
    });