Red Brick Fire Balls Over High Barriers

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Red Brick Fire Balls Over High Barriers

Post by Erockbrox on Sat 27 Jul 2013 - 3:49

Okay, I think I'm going to let one cat out of the bag here.

So a while ago I was making some puzzles for Quest for Calatia and I used to always just think that the red fireballs that come from the red brick couldn't go over any of the high barriers in the game.

As far as I know, there are low barriers, which allow projectiles to pass over them and high barriers, which do not allow projectiles to pass over them.

So normally anything that is a high barrier will not allow a projectiles to pass over/though it. If you make a red brick and destroy it while its on the floor then anything with a high barrier will block the shot, but there is one special case when a shot will go though.

If you take a red brick and then pick it up and then throw it at a horizontal high barrier and then destroy it in mid air then it WILL pass though! And this is the only case where this happens. If you try it on a vertical high wall it doesn't work.

So what does this mean, it means that I could possibly break a puzzle of yours or get to places in your dungeons that you didn't intend for me to get to by exploiting this. Like in the following picture that I sent to Gamemakr explaining this to him. If you think that this pegswitch was protected then think again. So everyone here should keep this in mind when designing.





The reason why I'm posting this here is because it might be useful to make a ASM hack which "fixes" this or doesn't allow this to happen for reasons that I stated above.
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Re: Red Brick Fire Balls Over High Barriers

Post by Conn on Sat 27 Jul 2013 - 4:38

This really is an interesting finding!
However, I must admit that I have no clue how to hack it that the brick shot won't get over the barrier. My best guess is that you'd have to code all the barriers to reject the brick at a former state (x/y) coordinates, but coding anything here would most likely result in a mess (at least if I'd go for this). The best to avoid is to (1) make a double barrier or (2) avoid horicontal access:

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Re: Red Brick Fire Balls Over High Barriers

Post by Puzzledude on Sat 27 Jul 2013 - 6:41

I knew this actually. The problem is the fact, that the authors of the original game wanted to make the main sprite not to bump into objects which you approach from the bottom. So all sprites go "over" slightly. If you hold a jar or red block above your head, you are one unit taller, than normally. But this is also infront of the object (so it must go visually over it).

So the big fence is 3 units, and will block everything with 2 units of hight. Holding red block above will make it 3 units and the beam actually makes it over the fence. So you need a 4 unit barrier.

No Asm will help, since the fence already is set to block your beam, you just managed to bring it over it. You can however try to make a type of a big fence a type 01, rather than type 39, but you will loose the "going over" effect and will bounce into the fence with the first pixel. This will be a visual paradox.

But the vertical has no such "going over" effect, since this is the right side. The right, left, and upper side have no such effects. But there is such an effect in the overworld. Approach your house from above, and you'll see what I mean. There the house must partially go over Link. This visual effect was reduced to big torches only in the dungeons.

Best possible solution to this is to make a 4 unit barrier (you can see this in Goddess of Wisdom hack). In the guardhouse you have such a barrier, but the peg is carefully blocked by big 4 unit objects (since I knew otherwise it will go through).

PS
You can hit that peg above with the bomb also, if the peg is to close and you make the bomb explode in mid-air, it will explode over the fence (but only a pixel or two).
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Re: Red Brick Fire Balls Over High Barriers

Post by Erockbrox on Sat 27 Jul 2013 - 6:54

Thank you for the insight Puzzledude, your explanation makes perfect sense.



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