Thanks! Phaser.io has a great tweening/animation system I use for some things, but the momentum animation was just a few lines of custom code. You basically just set the angle to a smoothed (distance travelled in last 500ms).
No problem! Of course the really awesome feature would be the ability to drag piles of cards and have it automatically determine whether there is enough space up top to do the swaps. (ie if you have 3 spaces open at the top-left, you can drag a 6543 onto a 7 in one step.) Similarly automatically putting cards up on the top right once they're exposed and there are no lower-value cards left. Obviously those would be rather more work though!
I use http://phaser.io for scene management (animated resizing of the game, tweening cards to predefined points on the table, etc) and the particle effects, as well as dynamically building the card images. I've been really impressed with Phaser.