Wind tunels in Labyrinth Zone (Sonic 1)

I have looked about it but I still didn't find the answer, so here is the question: How could I add another wind tunels in Labyrinth Zone?

 

I think it's activated by Obj0C, the door object.

 

I'm sure there's a tunnel somewhere in Labyrinth Zone that doesn't force you through. I don't think this tunnel has a door, unlike the other wind tunnels.

 

Adding a wind tunnel is kind of tricky.


I won't detail much but here are some infos you'll need:


- Each level in labyrinth has 1 wind tunnel excepted for the first one (level 0) which has two. Each wind tunnel data is made of 4 words (left, top, right, bottom).


- The address of the data in the array is calculated by multiplying the level number by 8 and adding it to the address of the array.


- The wind tunnel array begins 8 bytes (4 words) before the "LZWind_Data:" label. This is a trick used to have two wind tunnels in act 1. That trick is the subq.w #8,a2 before loc_3E56.


- The number (minus one) of wind tunnels in the level is moved in d1 in the routine, this is used for the loop so in level 1, it checks two positions rather than one.


- The LZWind_Loop routine compares Sonic's position with the coordinates given in the array.


So, in order to add a wind tunnel in a level, you have to modify this system so rather than using only one wind tunnel per level, it can use as many as you want.


For example, you could add an array with the number of wind tunnels in every level minus one (eg: NbOfWindTunnels: dc.b 1,2,0,0 ; for 2, 3, 1 and 1 wind tunnels), move that value to d1 to make the game loop as many times as necessary for the given level, then use this array to calculate and modify the address of the data to use.


It should be simple enough, you only have to modify things from LZWindTunnels to loc_3E56 to use an array for the number of wind tunnels and modify the LZWind_Data array accordingly.


edit: corrected a mistake (bytes/words)

 

Interesting information. Let's see if I can do something with this.


Thanks a lot SpirituInsanum!