Hi, I will answer some of your thoughts
It would still be better as an applet - I personally hate downloading rar files.
Well, there is no applet because I actually don't know how to make an applet from processing code in netbeans. The game is for Android and therefore I haven't messed with applets yet (I'm new to Java, I grew on C++, so I don't know all the concepts of Java)
As mentioned elsewhere it definitely needs sound.
Yes, I understand now, I will work on it next week when I'll get back from trip.
Not sure if it's possible but could there be a computer opponent that could move and that you have to hit.
I was thinking about it, and I may add it when I'll have spare time
Could the space ship be also moved using the same mechanism as the meteors? This may make the game too difficult though.
I'm sorry, I don't quite understand this one, nevermind

A build your own levels might be interesting and you could have a way of making them public.
And this is another thing that crossed my mind, but the problem is, how you assure that the levels created by people will be playable? (Or they won't be copies of other levels?) Maybe the best way would be to make online editor where you can submit your levels after you can complete them, and when I want to make an update, I'll go through few levels submited and pick the best ones.
Perhaps a sun graphic that sets fire to meteors (either destroys them or you get extra points for a flaming meteor).
Well, meteorites could get more interaction maybe, something like in angry birds, when you would click on meteorite, it would break into three pieces or something similiar.
Another of the wall idea might be worm holes where you go in one end and come out the other?
I'm not sure how is copyrighted blue/orange portal from portal 1/2 (I mean, the graphics). But I could ask my friend to draw me these portals in 2D, maybe animated, and they would do this kind of teleporting. The problem however is, that screen on mobile is small and if I want to put the whole level on it, it would be difficult to find a interesting use of portals there.
Also how about a little cross to say where you last fired?
I should have added this feature on release, but it's different using your fingers than mouse (with mouse, you are precise, with fingers you are not, so even if you saw where you clicked last time, it would probably be not so helpful)
Could some of the pencil drawings actually move and affect the game in some way?
Teoretically, they could, maybe som kind of a monster flying around and eating meteorites? Yes, that would work, but the problem is again with the screen size.