Captcha replacement

I stumbled upon http://www.kettletime.co开发者_运维技巧m.au/chance where the user needs to drag and drop a box with a number into another box to prove that he is human.

How do you implement this? Any free library to do this?

Thanks

It appears to be this one: http://www.webdesignbeach.com/beachbar/ajax-fancy-captcha-jquery-plugin.

How do you implement this?

Of course, you can implement the functionality on your own (see other answers), but this plug-in seems to be highly configurable :)

Any free library to do this?

Yup, see link above.

I suggest using jQuery library with jquery UI official plug-in. Here is a demo and code:

http://jqueryui.com/demos/droppable/

You should take a look at JqueryUI. The have a direct drag and drop implementation.

http://jqueryui.com/demos/draggable/