This only works on Yoshi's Island U 1.0 ROM!! Unzip all files in ZIP into a folder somewhere. Download latest asar (minimum v1.37) and place that in the same folder. Also put a Yoshi's Island U 1.0 ROM in that same folder. Double click asar.exe and type in emptynest.asm for patch name, and your U 1.0 Yoshi's Island ROM name. Press Enter.
This patch is a combination of several small hijacks / modifications.
See emptynest.asm for some detailed comments explaining it all.
Now there is a new way to die since Baby Mario is removed.
The star counter now acts as Yoshi's "health".
Getting hit by something decreases it by a value in the damage table.
The damage table contains one value per sprite, so damage can be customized per enemy.
When the star count reaches 0, Yoshi dies.
Stars and middle rings still increase it, so they now act as "health".
A reasonable damage table has been chosen as a baseline/default, but feel free to modify as you please.
It is located in damage_table.asm and has convenient names for the sprites too.
Note that enemies who didn't cause Yoshi to be "hit" and lose Baby Mario in vanilla will also not
cause damage here, but you may modify sprites to cause a "hit" and then they will pull from the table.
Some methods of damage are not yet implemented because they differ from the standard Yoshi being "hit".
These are marked in the damage table, so please read the top of damage_table.asm for more information.
Transformations rely on certain Baby Mario attributes,
but these have been fixed; it completely does not show or rely on Baby Mario.
Also note that Yoshi now loses health while transformed.
Super Baby Mario and Skiing Yoshi still display Baby Mario's graphic,
but both of these are technically "Yoshi" in the code's perspective.
Graphical patches would be required to completely graphically remove
Mario as well. NOTE: The big "Yoshi" egg during Super Baby Mario is
actually "Mario" in code, so this has been removed also.
-Add support for all the baby-stealing sprites like bandit, and really anything
that is nonstandard damage like Hootie and the Blue Fish.
-Add a table for objects that damage Yoshi, e.g. icicles and wooden spike/stakes.
-The Yoshi block after transformations doesn't act exactly like the vanilla game,
because it relies on the bubble of Baby Mario to float up and return to; currently
in this patch it just returns you directly to where the block is. Would have to
simulate a bubble somehow and use that as a return point to fix this.
-Star counter is broken in Prince Froggy boss fight and also shows "behind"
certain objects, like in 1-2 helicopter section.