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About ForceInfinity

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    Space Invader
  1. Since strikes are 10 + result of next two rolls. Spares give you 10 + the result of the next roll. So for a scenario where you have the following, where you hit spares on every frame except for the 10th frame where you strike out. In the following as you hit each 9, you can do a look ahead to see your bonus roll, and add it to your frame total. When you get out to the 10th frame, if you strike on the first roll, we stop counting there and look ahead at the next two rolls. 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 1 9 1 9 1 9 1 9 1 9 1 9 1 9 1 9 1 9 10 10 10 So all that said, your first frame is a spare. To populate the first frame, you do the look ahead for the one roll which is a 1 so your first frame is 11. Second frame calculates out the same, so it ends up going 11, 22, 33 until you get to the 9th frame. You get the spare, so you look ahead to next roll which is a 10, so add that and you're at 108. Get to 10th frame, you see the strike and stop there, but then do the look ahead to the next two rolls (which are themselves strikes) What about spare strike in the 10th? The spare looks ahead to the next roll (slot 20) which is the strike (so there's your 20). 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 1 9 1 9 1 9 1 9 1 9 1 9 1 9 1 9 1 9 1 9 10 Not sure if that makes 100 percent sense. Sorry for all the edits. Going a little too stream of consciousness for my liking. Bottom line is you need an array. Nothing fancy. Just enough to hold 21 rolls
  2. azure (greetings from another fellow Puget Sound resident), Thanks for taking the time to reply. Despite being a software engineer, when you've done nothing but higher level languages all your career, when you step into assembly as a newbie and try to reverse engineer something for the Atari... Well it's been an interesting endeavor. Part of the challenge is trying to map out what is going on in memory. So far the only area of RAM I've not fully accounted for with some measure of confidence: 9A - 9F AF - B9 C5 C7 - E9 F6 There were a couple of things I would've loved to have done with this game, which would be pretty tricky to do with the available RAM space. 20 bytes for the lower horizontal scroll, 18 for the upper, 6 for the two player scores, another 6 for the player score sprite pointers, 6 for stack space, and that's nearly half the RAM out the window. The other interesting insight was that the enemy bullets are using the Ball graphic (which is why the bullets tend to take on the color of the landscape color layer) One of the things I do want to see if its possible to do is hack the game to do the City of Mystery the way that's closer to the arcade; first to make it harder to get that shot through to the Gond; maybe seeing if its possible to use two GRP1 graphics that are horizontal lines with a gap. The sprite size would be set to maybe 4x and use LSR and LSL operations to scroll the openings. The final part would be far more tricky and that's to do the bottom barriers in the same way the arcade did, and with RAM space being at a premium, I may have to use lookups in ROM to pull that trick off (and that may likely mean trying to do this game in a 16kb space rather than the current 8kb) It is fun trying to dig into the mind of the engineer, because I can already see that in some ways, he had to devise some pretty clever tricks and some strategic byte packing to pull this game off. PS - regarding the boss being too trivial, I can say that in the arcade, the city of mystery was also pretty trivial if you're ready for it and you're centered on the screen as the Gond is scrolling in. If you're mashing that up button, you'll take him out almost immediately.
  3. So I was reverse engineering Vanguard and noticed that they were zero padding a bunch of lines above the player sprite. I'm assuming from when I was looking at the code that they used the scanline (Y register) along with RAM 84 indirect basically draw the sprite at the correct point in time. Many of the enemies seem to have 14 byte gaps between the graphics as well and it seems like it's a waste of ROM. Was this common practice? I'm presuming they did it this way to preserve a register, but still learning the ropes. Still bugs me to this day that they couldn't have figured out a way to assemble at least a passable sprite object for the Gond in the city of mystery. I also had a couple of other little tricks I wanted to try with the game once I have a better grasp on how its RAM is getting used and how the main game loop behaves
  4. With the forum migration, the original set of links no longer apply, so I cobbled these together so Andrew Davie's wonderful tutorials can once again be more easily discovered. Session 1: Session 2: Session 3: Session 4: Session 5: Session 6: Session 7: Session 8: Session 9: Session 10: Session 11: Session 12: Session 13: Session 14: Session 15: Session 16: Session 17: Session 18: Session 19: Session 20: Session 21: Session 22: Session 23: Session 24: Session 25:
  5. I finally got to attend that expo, and I must say that it was a surreal experience to finally meet some of the people behind those games that I played so many hours upon. All were great people in person and as a software engineer, it was really cool to nerd out with David Crane, if only for a couple of minutes. I ended up finding a Defender 2 cart in the wild, so I snapped it up. Yeah, the rain was a bit much, *especially* Saturday night as Portland was getting hit by a pretty good rain storm. Still all the same, I was glad I was finally able to make it out. Will be back out for 2018 to be sure!
  6. Loved Beamrider. I would add Defender 2 (Stargate) and Enduro. Maybe Midnight Magic
  7. Was able to meet HSW, Gary Kitchen, and David Crane. All great guys. As a software engineer, it was awesome to be able to nerd out with David Crane for couple minutes

    1. GoldLeader


      That is Pretty Cool!

  8. Odd, I never found Yar's Revenge to *ever* be that crazy considering that supposedly on the hardest difficutly level, I could flip the score over like crazy with just some simple timing. Got bored and shut the game off after about 13 mil or so
  9. Actually the games that bothered me were NFS Underground 2, but the worst goes to Swat 4. Supposedly the put a patch into the game that not only puts in game ads, but tracks how long you look at those ads in game. Now *that* is a bit much IMHO SeanB
  10. Since I've not seen this tossed in, I'd add Stargate (Defender 2) to the list as probably one of the more intricately design games since you had all the enemy types with graphics that weren't all that far off from the arcade counterpart, all the weapons, two joysticks, the radar, the 4 humainoid stargate warp trick, the showdowns, etc. They really nailed that one. My question was concerning the supercharger vs. Pitfall 2. What was it about Pitfall 2 that made it cheating as far as the hardware goes (as some would argue is the case with the supercharger)
  11. This one question's always been bugging me since I owned the 2600. I've yet to encoutner a 2600 game that showed a 7 digit score. Is there a technical reason behind the 6 digit thing or why there's never been a game with 7 digit scores?
  12. I always thought Video Pinball was way too easy....launch the ball, get it stuck in the bonus chute, and keep it there indefinitely through the nudge. More or less could flip the score over endlessly....and got tired after about a couple million or so I also thought Yars Revenge was too easy...
  13. I had a question and was wondering if someone with some knowledge of the innerworkings of the game or maybe HSW could lend insights to this. Back in the day when I wasted way too many hours on this game as a kid, I was goofing off with it and actually got the countdown going for the mother ship. I also managed to call out Eliot as well. What happened was that I managed to get it to where Eliot was in the forest right as the ship got there. When that happened, it was strange because the Eliot disappeared, the ship was in its place, and the game became stuck. Anyone know why this would happen? Was just curious what the story was with that. SeanB
  14. Was there ever a game on the Atari 2600 that actually did NOT roll over at one million and actually went to the 7th digit? Was there some hardware or physical reason why it seems like none of the games on the Atari 2600 ever went pass a million? That question (abliet minor one) has bugged me for some time. Thanks
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