Donkey Kong Country Expresso bug

If it has bytes, we can change it. Talk about anything relating to hacking and emulation here.

Moderators: General Moderator, Game Moderator

Donkey Kong Country Expresso bug

Postby Assassin » Wed Jan 06, 2016 9:06 am

As with Donkey, Diddy, Rambi, and Winky, Expresso can be made to walk with the arrow buttons, and to run by holding them down with the Y button. However, due to a couple of cases that make him run all of the time, it's easy to think that walking isn't an option. Using Barrel Cannons (such as when emerging from the bonus area in Temple Tempest with Expresso) or jumping and flapping your wings will put the bird into an always-run state. As the ostrich is very fast, this can compromise control some, and increase your chances of moving into a ditch or an enemy.

To reliably disarm the bug, dismount, have your Kong move around until he stops auto-running, then remount. However, it'll be re-enabled every time you flap.

What's happening is that the game will continually set an "Auto move faster" flag (Bit 1 of 7E/169A for Donkey, $169C for Diddy) from the time you flap your wings in mid-air until you land. (This is done at BF/97B2 in USA Version 1.2.) Presumably, this is to let you fly faster and further without having to hold Y, as holding one button while pumping another with the same thumb is a pain in the ass (see Super Mario Bros. 3, Level 6-5). While the flag is no longer repeatedly set when Expresso is on the ground, it doesn't get cleared, either. It does with a Kong (albeit after a possible delay). That's why you'll need to dismount to allow walking.

The flag also gets set by jumping off of a rope, which is another kind of mid-air jump. (I don't yet grasp the reasoning behind this or the Barrel Cannons' setting. I'd have to study game behavior with it never being set.)

Regarding a fix, I'm too clueless of this game's internals to know where to put it. Because BF/97B2 sets the bit continually, I might be able to get away with continually clearing it shortly before the containing function is called, but that's cheap and risks affecting too much.

I discovered this bug circa July 4, 2006 or sooner, but inexplicably never typed up a post. Google searches and looking at a few good webpages comes up empty, which makes me think that this one is so pervasive, players don't even realize they're being deprived of walking.
Last edited by Assassin on Mon Feb 22, 2016 6:55 pm, edited 2 times in total.
Reason: few more minor changes
User avatar
Assassin
Moderator
Moderator
 
Posts: 1195
Joined: Tue Sep 14, 2004 5:10 am

Re: Donkey Kong Country Expresso bug

Postby Assassin » Sat Feb 27, 2016 1:06 am

It turns out Rambi is also affected by the Barrel Cannon form of the bug. Now, there aren't many Barrel Cannons in Rambi levels, and he obviously can't flap wings, so you'll encounter the issue less with him. It's still remedied the same way: dismount, have your Kong move around until he stops auto-running, then remount.
User avatar
Assassin
Moderator
Moderator
 
Posts: 1195
Joined: Tue Sep 14, 2004 5:10 am

Re: Donkey Kong Country Expresso bug

Postby Assassin » Wed Mar 02, 2016 3:17 pm

to round out the trifecta, Winky indeed has the flaw as well (triggered by Barrel Cannons). test it on a level like Bouncy Bonanza, as Winky's Walkway is unique in having a Non-Blast Bonus Return (which initially threw me):
http://www.dkc-atlas.com/dkc/levels/2-1

the bug's disarmed the same way as with the other two animal buddies.
User avatar
Assassin
Moderator
Moderator
 
Posts: 1195
Joined: Tue Sep 14, 2004 5:10 am

Re: Donkey Kong Country Expresso bug

Postby Imzogelmo » Wed Apr 20, 2016 2:16 pm

Assassin wrote:holding one button while pumping another with the same thumb is a pain in the ass (see Super Mario Bros. 3, Level 6-5).


Before I even read ahead, I was thinking of that exact level. Am I the only (other) one?
User avatar
Imzogelmo
Veteran
Veteran
 
Posts: 659
Joined: Wed Sep 08, 2004 4:07 pm
Location: On the spirtual plane

Re: Donkey Kong Country Expresso bug

Postby Assassin » Thu Apr 21, 2016 11:56 pm

you can't be, unless everybody else has longer and/or more pliable thumb-ends, or they somehow knew to switch to a two-fingered approach without any trial and error.

now i need to figure out how to consolidate the first three posts, without burying the lede. while it makes sense to explain how the game errs after providing the "Auto move faster" flag setters and clearers (which'll avoid repetition), pushing the crux of the bug out of the 2nd and 3rd sentences might have some readers get lost.
Last edited by Assassin on Fri Apr 22, 2016 9:34 pm, edited 1 time in total.
Reason: minor tweak
User avatar
Assassin
Moderator
Moderator
 
Posts: 1195
Joined: Tue Sep 14, 2004 5:10 am


Return to ROM Hacking and Emulation

Who is online

Users browsing this forum: Google [Bot] and 2 guests

cron