 
 class AATrickViewController: UIViewController, UICollectionViewDataSource, UICollectionViewDelegate, UICollectionViewDelegateFlowLayout {
     // Properties
-    let cellReuseID:String = "cellReuseID"
+    private let cellReuseID:String = "cellReuseID"
     private let numCols = 4
     private let numRows = 8
 

        if currentCardKey == nil {return UICollectionView()}
        
        let layout = UICollectionViewFlowLayout()
        layout.minimumLineSpacing = 1.0
        layout.minimumInteritemSpacing = 1.0
        layout.sectionInset = UIEdgeInsets(top: 10.0, left: 10.0, bottom: 10.0, right: 10.0)
        layout.estimatedItemSize = CGSizeMake(30, 30)
        
        
        let collectionView = UICollectionView(frame: CGRectZero, collectionViewLayout: layout)
        collectionView.delegate = self
        collectionView.dataSource = self
        collectionView.registerClass(UICollectionViewCell.self, forCellWithReuseIdentifier:cellReuseID)
        collectionView.backgroundColor = FlatUIColors.randomFlatColor()

    func collectionView(collectionView: UICollectionView, didHighlightItemAtIndexPath indexPath: NSIndexPath) {
        let cell = collectionView.cellForItemAtIndexPath(indexPath)
        cell?.backgroundColor = FlatUIColors.pairedColorForColor(cell?.backgroundColor)
        setViewBackgroundColorToCell(cell)
    }
    
    // change background color back when user releases touch
    func collectionView(collectionView: UICollectionView, didUnhighlightItemAtIndexPath indexPath: NSIndexPath) {
        let cell = collectionView.cellForItemAtIndexPath(indexPath)
        cell?.backgroundColor = FlatUIColors.pairedColorForColor(cell?.backgroundColor)
        setViewBackgroundColorToCell(cell)
    }
    
    func setViewBackgroundColorToCell(cell:UICollectionViewCell?) {
        guard let unwrappedCardKey = currentCardKey      else {  return  }
        guard let cardView = cardViews[unwrappedCardKey] else {  return  }
        cardView.backgroundColor = cell?.backgroundColor
    }
    
    // MARK: === UICollectionViewDelegateFlowLayout ===
