good but a suggestion

To me It looks like the lava is like a giant wall. to me I think if the lava is below the platforms u could try and do like a balanceing thing where if u start to get too close to the edge your ball might start to fall towards the edge. and u could have a chance to get away from the edge before your whole ball falls in.

Very short

But good.
However, the collisions appear strange to me, sometimes. Instead of being pushed to the chasm, the ball blocks on the moving objects.
Also, I think, the last level is so easy that it should be moved closer to the beginning.
In addition, I believe, you should add some extra challenging levels to the game.

Pretty decent game!

The only thing I would say to improve is the death scenes

Room to do more

Besides the obvious of adding about 20 more levels, you should really add distinct physics for each type of ball that you provide. For instance there is a big difference between how a soccer ball, wood, and concrete would roll, bounce off objects, and stop, especially on the three different surfaces on the levels. At the beginning of each level you could give a preview of the surface and the player would then have to select the appropriate ball to best complete the level. That alone would add a lot of depth and addiction to the game with more levels added. And fix the ball getting stuck in obstacles. And maybe add a little more "duty" to the ball, like collecting things. You have to remember there are a lot of games like this out there and yours has to be distinct and provide a little something new.

As far as these types of games go...

I think you did a pretty good job, man. The only thing is that I find in other games, you can hop sharp corners or simply roll over them whereas in this one if you so much as a touch the edge, even if you're clearly anchored on the surface, you'll have to start over.. which makes it a bit more limited than I'd like. But otherwise, other than a couple of the glitches that come with something fairly rushed (which I'm assuming it was considering it was for a school deadline and there are only three levels), that comes with the territory.

Keep it up and keep working to do better =]