JohnE Posted March 16, 2019 Share Posted March 16, 2019 Hi all, This is my first post on AtariAge. I created a version of Berzerk with diagonal shots. This has been done previously by Dennis Debro. This version is based on his disassembly, and I borrowed and learned a lot from his hack. Debro's hack, as I understand it, works by extending the robots' "missile box," which has to do with how close the player must be to the robot before the robot fires, both in the horizontal and vertical directions. Extending this makes it possible for the player to be close enough in both directions, even from a good distance away. In that case, a diagonal shot can be fired. (Debro also added code to combine the two missile directions.) This code is quite interesting and educational, but the actual game play is still disappointing. The robots very rarely fire diagonal shots. In addition, increasing the missile box makes the robots dumber, so that they often fire wild shots that are not even close to the player. Since only one robot can fire at a time, this ends up making the game easier. I wanted to make the game harder! Specifically, I wanted to stick to the original algorithm and only fire diagonal shots when normal shots would not be fired. However, this would seem to require a separate routine to compute diagonal shots that doesn't rely on the original missile box, and there is not enough space on the 4K ROM for such a large amount of code. So my solution was to add such a routine to a second bank, making an 8K ROM. Even then, it was hard to squeeze in enough code just for entering and leaving this second bank, but I finally managed. Debro's marking of unnecessary bytes in the original ROM was very helpful for this. Anyway, here is the modified assembly and binary. The robots do frequently fire diagonal shots, and the game is harder! I'll let you decide how much harder. This hack only includes the diagonal shots. It does not include the other changes that Debro made in his hack. Debro's original disassembly and hack can both be found at: http://www.bjars.com/disassemblies.html berzerk_dshots_johne_mar_16_2019.asm berzerk_dshots_johne_mar_16_2019.bin 6 Quote Link to comment Share on other sites More sharing options...
neotokeo2001 Posted March 17, 2019 Share Posted March 17, 2019 Played several games and the diagonal shots work great! I like the harder game play. Did not see any issues. Sharing with the Atari 2600 Homebrew group on FaceBook. https://www.facebook.com/groups/Atari2600homebrew/ 2 Quote Link to comment Share on other sites More sharing options...
Mononym Posted March 17, 2019 Share Posted March 17, 2019 thank you JohnE, never been so happy to die in that game before! Quote Link to comment Share on other sites More sharing options...
Zoyx Posted March 17, 2019 Share Posted March 17, 2019 Thanks for adding this. Always thought that the original Berzerk was too easy. Quote Link to comment Share on other sites More sharing options...
Zoyx Posted March 17, 2019 Share Posted March 17, 2019 Is there a way to add more playfields? I think there is only 4. Doubling that would be awesome. Also might want to add a watermark so people know that this is a modded version. Quote Link to comment Share on other sites More sharing options...
JohnE Posted March 18, 2019 Author Share Posted March 18, 2019 So glad to hear that people like the game! Thank you all for testing it. Zoyx, I haven't yet looked into adding more playfields. Also, I'm not clear on what you mean by "watermark." What did you have in mind? Quote Link to comment Share on other sites More sharing options...
doctorclu Posted March 26, 2019 Share Posted March 26, 2019 Not bad. Adds a little more challenge to the game, though I have yet to be hit by a diagonal shot. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.