Short answer: you can easily make nearly any shape and visual effect in Xara Xtreme (excepting perhaps a helix), but the kind of animation you want may be better done in an animation authoring application.

Xara uses key frames and tweening for Flash output. If you can identify key frames in your concepts and allow the program to generation intermediate frames, you will be happy.

However, full interactivity, complete control over what happens when and such like will be yours only with a timeline-based program. I suggest Swish, unless you have a lot of money and a lot of time to learn Flash in Adobe Flash.

You can see a movie on Flash in Xara Xtreme at http://www.xara.com/products/xtreme/demos/

There are plenty of tutorials at XaraXone http://www.xaraxone.com/html/tutorials.html -- July 2007 one has a Flash tutorial.