Wow that is even more impressive because, and I quote the programmer:
The C64—due to its lower clock frequency—is slower than the Atari 800XL and has a more complex graphics representation. So, the challenge to make the emulator more or less fast enough on this small 8-bit home computer was really a big one for me.Yep....there is no denying which machine was better

I'm a bit puzzled why he is calling it emulation by the way because as he says himself, the processor is actually simply running the original Asteroids code. The only thing emulated is the "surrounding hardware" of the original Asteroids board. In that way it is more like JROK's Multi-Williams board !

The programmer wrote this for ABBUC (the german Atari user group that exists ever since the 80s) 2012 software contest and only became third, I really wonder which programs can be more impressive than this one !!!!!
Of course another cruel thought came up with me: would it be possible to output the analogue signals to run an actual vector monitor with it.....maybe a bit pointless but technologically definitly a challenge..... I wonder if the POKEY could provide (a basis for) those signals because it is known that you can drive vector displays (or oscilloscopes) with PC sound-cards.
Or maybe some external DACs would be necessary...