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Posted: 8/6/2018 3:33 AM
Post subject: Disney's The Little Mermaid
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Jigwally
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Posts: 119
Hi, I'm looking at the current TAS and I noticed that two of the boss fights (Shark and Walrus) have fairly trivial improvements that are already used in RTA runs. For the shark you wait on throwing the 3rd fish at him until he reappears at the other side, & hit him on the same frame that the 2nd set of fish is spawned. For the walrus you have to save the 2nd shell he gives you from the first cycle and hit him with it on the same frame that he spawns the 3rd shell. Otherwise you are just delaying them from these spawns. I think McBobX might have done this for mid-fight RNG manip but I have been doing disassembly of this game and I'm confident enough in my understanding of how the RNG advances that I can prevent this from being necessary. The RNG is 4 bytes ($E4-$E7) which are automatically advanced each frame, but are also altered a certain way each time they are pulled by something requiring an RNG check. So to alter RNG you can either simply wait a certain number of frames before entering the boss screen, or you can vary which frame you pass by an enemy that uses an RNG check to cause the RNG to diverge differently. I also suspect that the RNG for most of the other bosses could be manipulated to be faster. For example, at the Seahorse boss the diagonal velocity that the enemies are shot at is an RNG check. In Ursula 1 the arc that the enemies are thrown at (the initial direction/velocity + the height they reach before falling) are also their own RNG calculation. One more consideration, if you are within 20 pixels vertically of the Shark there is a 50% chance he will not spawn the fish that cycle. I've only just recently begun to learn how to do game disassembly but this is a game I'm very passionate about so I'm really hoping I can make some practical use of what I've decoded so far.
Posted: 8/6/2018 4:39 PM
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Jigwally
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Posts: 119
Thanks for putting this in the original thread, I tried to find it earlier but couldn't I've learned some things looking through Randil's notes that will help me out
Posted: 8/6/2018 7:04 PM
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Jigwally
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http://tasvideos.org/userfiles/info/48979630092480048 19 frames cut to start
Posted: 8/12/2018 3:14 PM
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Jigwally
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Possible small improvement: Your x and y subpixel values carry over from the end of the boss fight to the start of the next level. So you could possibly shave some frames by maximizing/minimizing these in advance
Posted: 8/28/2018 9:23 PM
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Jigwally
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Joined: 3/11/2012
Posts: 119
Discovered something interesting with the Eel fight (& possibly other fights): The crab spawns usually take either 60 or 120 frames before they start walking & can be bubbled, which is determined by RNG. However the RAM value used for this is also used as a timer for bubbled enemies to determine how long they stay in place before they start floating upwards. This value freezes in place once the bubble is grabbed by Ariel. What this means is, if a crab is spawned in the slot previously occupied by a bubbled enemy, it will use the preexisting timer value instead of wiping it and randomly generating a new one. So if the bubble had 100 frames left on its timer when it was grabbed, if the bubble is popped and a crab spawns in the now "empty" slot it will take 100 frames for it to go to its walking phase. You can actually see this happening in the published TAS. In the third pair of crabs their timers ($46B and $46C) are preset at #$69 and #$B4 respectively because these were the previous timer positions of the bubbles previously occupying these spots.
Posted: 12/17/2018 12:44 PM
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Jigwally
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Joined: 3/11/2012
Posts: 119
My first draft is 138 frames faster than the current TAS. I need to improve the Ursula fights, I lost 78 frames on them. Other than that I've improved every level. http://tasvideos.org/userfiles/info/51926926619766635
Posted: 2/18/2022 6:54 PM
Post subject: Little Mermaid (NES) All Secret Rooms Location
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XTREMAL93
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Location: Azerbaijan, Baku
There are 3 Hidden Rooms in the game Link to video
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