Techniques used in "algebra touch"?

[new2objectivec]

Hi Guys,
Saw this very nice algebra learning program called
Algebra Touch. From the YouTube video on the site, you can see the User Interface design really smooth and clean.

A few questions about the techniques used in the application:
1) how do you create the text (or label or image?) in the equation that's movable/draggable?

2) when the "+" or "*" sign is touched (to combine/calculate) or a number dragged to other side of equation, it nicely faded out and then another new one appeared, what are the skills involved to create that kind of effect?

3) from the screen design, there seems to be some sort of "anchor" point in the middle line which when you dragged the numbers near the "acceptable" position, it automatically moves to that point, how can that be done?

Any suggestion/ideas welcomed, Thanks a lot!