You cannot assume that a game will just run on older hardware because it’s not as graphically enhanced as other games.
It’s definitely not the problem, as I have a Radeon HD 4670, it’s 6 years old (a gen behind yours), Fraps reports solid 60 fps (at 1080p). CPU is a Phenom II, but this game appears to be (not going to break out the decomplier, have things to do) single-threaded, so the quad-vs-duo thing doesn’t matter a whole lot.
I’m not disagreeing with you, aside from the ‘too much for Java games,’ as I’m honestly puzzled as to why you’re getting such poor performance.
That said, full-screen should be an option here, if not only to figure this out.
I have been listening to the music of this particular game (AstroRock) this past 2 days. Love’d it since the first time i heard it.
Maybe you can get some ideas for your game from this one, it was a fun game. You could even get it somewhere on the internet
4JtBQ4u4BXs
Thanks for all your feedback, I’m glad it works at least for some of you.
I’m sorry some of you have all these problems, I’ll try to figure out how to fix them.
You only need 4 textfiles: highscore, and savegame1-3. If they’re empty or something’s wrong with them it will automatically clear them and recreate them.
At least that’s what it should do.
@saucymeatman and BurntPizza:
I find balancing is one of the hardest parts in a game, but I will try to improve this. Thanks for your tipps.
The game is fixed at a resolution of 1920x1080, and I just scale it up or down depending on the actual screen resolution.
@ricardo: What do you mean with real fullscreen? What is not real about it?
/edit: I might have found a solution for the IllegalStateException. I never had the error, so I don’t know if it’s fixxed now, but I hope so.
Downloadlink above is updated.
/edit2: Maybe I should not forget putting the save folder in it. Sorry 
@bene What do you mean with real fullscreen? What is not real about it?
A window with 1920x1080 is not full screen. Yes the window fits the whole screen, but is different from real full screen.
Also, to improve performance, you can create your game in 800x600 and scale it up, instead of 1920x1820 and scale it down. Or one option to change resolution in-game.
This is just my opinion. Personally, I like to make my games in 600x480 or 800x600 and scale them up. And enable full screen (I don’t know how to do this in libgdx, but in java2D you only need two lines of code).
I did it this way, but there were so many problems with it. I removed the fullscreen-mode now, hoping there will be less errors/black/gray/white screens.
You’re right, I could’ve just made it in 800x600, I just didn’t think about performance there.
As I said in the first post, this is my first game I’m really publishing. Now I’m aware that “runs on my PC” doesn’t mean “runs on everyones PC”.
Next time I’ll test it on different machines, sorry for all the problems.
Here’s the windowed version, I’ll replace the link in the startpost as well.
http://www.file-upload.net/download-8669851/Asteroids.zip.html
I also added some sounds, but some will follow. Thank’s to BurntPizza, this site is great.
The new version runs properly now. theres way too much going on for me to be able to keep playing though!
Everything works fine now.
Very hard and addictive 
I found one error with one quick fix: If we lose all lives we spawn again for a short moment before main menu. Make our spaceship invisible.
EDIT: No sound here.
Items should be more expensive. With 40 min of game play I already have everything maxed out. Add more items like shields, more bullets, extra life, more powers like wave of bullets etc.
Really nice game, if you polish it more and add more stuff you can even sell this.
I have to say, your UI looks really nice!
I am following the same tutorial you used. Does he cover how to do such nice fonts and UI in later parts, or how did you accomplish that?
Thanks for your feedback.
@ricardo: I know, as I said I find balancing pretty hard. I think upgrades like firerate or number of bullets (which is kind of like doubling the firerate at the first level) are a bit OP and I’ll make them more expensive.
Thanks for your tipps 
@digdugdiggy: For the font I just went to dafont.com. I think in the tutorial is covered how you do things like a menu. If you have any specific questions about it PM me and I can send you some sourcecode if you want.
This is impressive.
The menus are fluid and great to look at and navigate, the UI is fantastic, it runs smooth.
This is honestly sellable, this is the kind of thing you could sell on GOG for a couple of dollars.
Very well done, I would like to watch a tutorial series on you creating this, it’s simply amazing, despite how simple.
EDIT: If I had one thing to say, use a simple encryption like Base64 for the saves. Everyone here will know the format but most don’t.
Thanks, I’m glad you like it.
Encrypt the savegames and highscore is definetely one thing I have to do, I’ll take a look at Base64. Thanks
In a full screen game I wrote I found it would run fine on some PC’s and just get a black screen on others.
I found running the jar with the option “-Dsun.java2d.noddraw=true” worked for me.
java -jar -Dsun.java2d.noddraw=true asteroids.jar
I’m afraid I haven’t tried your game yet though.
Mike
I read something about these command line parameters too, but I thought I can’t expect that someone who just wants to play needs to start it this way.
I added some stuff you suggested me:
-Sounds (Thanks to BurntPizza, http://www.bfxr.net/ is a very cool tool)
-the small enemy has now a shorter range, and shoots less precisely
-the dificulty increases now every 15 seconds instead of 10, so it should be a bit easier now
-some upgrades are more expensive
-savegames and highscore are now encrypted (Thanks to Gibbo3771, Base64 was easy to use and works great)
Thanks for your feedback
http://www.file-upload.net/download-8678635/Asteroids.zip.html
Aww yeah, this is pretty damn fun, that barrage of arcade-y audio goodness is great. Only sound effect that didn’t seem to fit was the menu button ‘click’, to me those are usually ‘two syllables’ if that makes any sense.
First time I got the ‘auto shotgun’ effect after deploying a special was unexpected and epic. You’re doing it right.
A few more things I noticed this time around:
Perhaps a volume control somewhere, or just a mute button? Also the music should probably stop if the game is minimized.
Be able to hold down up or down to scroll through letters when entering your name
Maybe not so much aimbot on the red ships? At least not at first, the difficulty suddenly goes way up when those guys show up, doesn’t feel smooth to me. Who knows.
Please add more extras. More bullets, more special attacks, shield, bosses, etc.
This is really a fun game, but to easy to unlock everything. You should add more extras and you can even sell this.
New Bullets is a good idea, but what kind of other special attacks do you suggest? I thought about a shield, but it wouldn’t be much of a difference to an extra life.
I’ll think about it, thanks
Just wanted to say that I’ve been playing around with this for the past two days. Maybe 45 minutes total play time and I really enjoyed it. And like others have mentioned, I think it gets too hard too fast, but other than that–this is great!
As others said, awesome game. It really encourages me as a beginner game developer, because it’s a really simple game, but professional-looking, polished and very enjoyable.
I agree with some of the other guys here that it gets hard too fast. And also that more ‘extra’ powers will be great.
I’ll also add that in my personal opinion, it’s too hard to control the spaceship. It’s too ‘slippery’, when it’s supposed to stop moving, that should happen faster.