Ballblaster 1984, I have two of them, one was sabotaged, and the other was dressed up to make the sabotage seem accidental. If you have 1984 in your collection, and you find the sequence "A9 00 8D 00 4D 4C 00 4B" near the beginning, this is the bad instruction in which "8D 00 4D" must be replaced with "EA EA EA". The other one has the sequence "4C 00 4B A9 00 8D 00 D4" which doesn't harm anything. Both sequences aren't part of the game, they are within the small "loader" routines found at the head of each one. Most programs have loaders tho they can be unnecessary and troublesome.
"4C 00 4B" is the command to RUN the game, at the end of each loader. The sabotage writes a zero to $4D00 immediately before RUN, this corrupts a specific math operation, not an illegal instruction, so the game might not crash but some thing won't be right. The second game writes zero to $D400 immediately after the RUN instruction, which doesn't make sense other than to disguise the first mistake as an accident, maybe a couple instructions and D's and 4's got transposed, nothing sinister. ? But the $D400 command (turn off PMG) shouldn't be in a Loop in a Loader, when PMG starts in the Off state already. The less harmful loader wasn't a patched bug fix, the two differ entirely. I'm not fooled.
The download file version 31104 bytes has a corruption, the last 195 characters were appended garbage, all $1A chr in this case. The better file becomes 30909 bytes long. We're talking about the 1983 beta version Ballblaster. Prior to the 1985 publication and name change to Ballblazer, there were (at least) 2 more beta versions named "Ballblaster early 1984" and "Ballblaster late 1984".
Few games offer such a simple scenario, primitive 3-D graphics, and yet give you the sense that you're really sitting in that Hoverpod. You know this is going to be something special with the most intoxicating theme music since M.U.L.E, which is in a league of its own. My sons always beat the starch out of me on this game because you've got to be really quick in your moves---I mean REALLY quick! This game is far superior to its other Lucasfilm brother, "Rescue at Fractalus". Yes, it's comparing apples to oranges---okay?! But I'll take the apples in this comparison. Get Ballblazer, find a living breathing opponent, and prepare to have about a hour of real competitive fun. Oh, did I mention this is a real time game with a time limit. That makes it really unusual! Enjoy!