Atlas Controls can be programmed via raw Javascript or via the declarative code model.
Initially the declarative code model may seem that you have to write lots of code but it makes things easy when it comes to complicated actions and behavious of the controls.
Look at the Hands on Labs
http://atlas.asp.net/docs/default.aspx
Atlas Asp.Net Server Controls are also available which writes all the script/ declarative code while rendering.
So life is easy.