Prototype: Is This Fun?

I found Xen and JigLibX, and am trying to better acquaint myself with them, so I made a quick Marble Prototype. There are still a number of bugs, largely due to continuing to learn more about Xen as I work.
The basic concept of the Prototype is a competitive marble game mode, in which you are being swarmed by marbles that blindly chase you off cliffs. You must survive as long as possible. The curent level contains a few relatively safe spots, to take a break, and the marbles that get dropped respawn immeadiately. The marble count will rise up to 15. I cannot currently restart, still solving some asynchronous update bugs, so restart the application to reset the marbles.
Let me know what you think.
Here it Is
It’s in XNA, so you will need the XNA Redistributable, .NET framework, and DirectX.
Be gentle it’s still in a VERY early form.
The Controls:
Arrow Keys to Move.
Space is a burst in the currently aiming direction.
Z dead stops you and makes you nearly immovable.
I’m trying to think of a direction I could take this, with general modifications, power ups, maps styles, other game modes, etc… And I want to know if it’s fun for someone who didn’t make it.