Well, it’s pretty awesome. A quote from the site, explains the awesomeness of this:
Since the nineties, arcade emulators like MAME can emulate the classics like Asteroids on the PC or the Mac. This program is an Asteroids emulator for the Commodore 64. The “emulation” of the arcade machine’s CPU is done natively by the 6510 processor of the C64. The video and sound hardware is simulated by the Asteroids emulator program. In this way, the original arcade game program is executed and interpreted, and the original game play is (more or less) exactly reproduced.
I can remember the disappointment in the conversions that showed up over the years of this amazing game. It was one of the first games I loaded in MAME to check out. Well Done Norbert!