Suggestion time!
As a "draft" for a game, it's not bad. But it needs more seasoning on the top. Let me suggest the following:
1) Better control of the ball. Players should be able to move with the arrow or WASD keys, and aim/shoot with the mouse. Maybe the ball doesn't have to bounce at all. I know, every Game Maker beginner gets excited with the "auto- bounce" feature, but it really isn't necessary. So arrow key movement/course setting should be one improvement. Also, make right-clicking do some "extra-powerful attack" of some sort, like a mega-bullet or something.
2) Traps (like spiked walls, moving spikes, meteorites etc) all over a level or some of them. It fills empty space and adds a challenge.
3) Power-ups: A shield, stronger bullets, extra lives etc would add even more diversity.
4) More enemies, or groups of existing enemies attacking together. I would also like to see bosses at the end of some levels!!
5) Faster game speed.
6) More music! The music you put may be OK to listen to your walkman, but I don't hink it fits in such a game. So try to add something that will not raise the hair on the back of player's necks after being looped >2 times.
7) Try to fiddle a little bit more with scripting, GML etc. It appears that you exclusively used the Drag&Drop system, which may be good for learning a thing or 2, but sucks major time if you want to actually make something decent.
8 Don't give up! Even if the end result sucks, you will have practiced for a better future project!
9) Don't give up!
10) Don't give up!
Good luck!
PS Did I mention not to give up?