It's a good start!
Being :04 seconds long, there isn't as much to review. But from what I do see, you got the starting basics right. You have an alright background, cool little worm, and give a good movement look and feel to the worm crawling around this desert. Not only that, but by adding the extra shrub that passes by as the worm crawls really made an addition to the effect. Also, kudos on making the shadow move with the worm and not just stay as one non-moving shadow.
But for next time there are a few things I'd suggest.
- Make the movie longer, or in other words, don't submit a "test". Rather, add some more and make it into a "short".
- Add more movement to the worm/shadow. This will touch up a little more detail.
- Also, adding little effects to the background could help. Such as have the shrubs move a tiny bit, or sand blowing around (depending on the scenery).
But above all it's a great start! Keep up the good work, and I can't wait to see what you'll have next.