Yoshi's Island Hookbill Koopa
World 5 is the fifth of six worlds in the game Super Mario World 2: Yoshi's Island and its remake Yoshi's Island: Super Mario Advance 3. It consists of ten levels two being castles, and two bonus stages (its extra level is Extra 5: Kamek's Revenge; its secret level is Secret 5: Items are fun!). It takes place on both the tops of snowy peaks, and in the clouds that surround them. They also feature bird-like enemies like Ravens, Goonies and Bumpties. List of levels[edit]
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Yoshi's Island Hookbill Koopa Games
Hookbill the Koopa is an enlarged Koopa Troopa in the game Super Mario World 2: Yoshi's Island and its remake. He is the boss of World 4 and resides atop the castle of that world. When Blue Yoshi and Baby Mario reach the bridge on which Hookbill is fought, a fog envelops the area, dissipating on. 4-8: Hookbill The Koopa's Castle. Regardless of score, you'll be treated to a cutscene on Yoshi's Island from the title screen and see Yoshi conquer the castle at World 4 before you're taken to the World 5 map screen. You can either begin World 5 now or try Extra Stage 4. Hookbill The Koopa Yoshi's Island - Part 19. Save hide report. 100% Upvoted. Log in or sign up to leave a comment log in sign up. View discussions in 4 other communities. No comments yet. Be the first to share what you think! More posts from the PromoteYoutubeGaming community.
Hookbill is the most technically complex boss in the game. He has a whopping 56 AI states, a skeleton for his body parts, one of which is drawn on a background layer, his body parts each have separate rotational values per animation frame, his graphics are mostly Super FX, and much of his processing is on the Super FX as well, despite even his 65816 code being over a quarter of a bank long. He touches on many, many aspects of the game's coding, lookup tables, etc.
Upon Yoshi's final hit onto Hookbill, there is code that governs exactly how much to move Yoshi's Y coordinate by. The basic formula comes down to this:
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The main two SRAM addresses here ($0058 and $0056) get computed/stored in Hookbill's Super FX code:
This code is necessary to be run each frame on Hookbill's final hit for proper placement of Yoshi. Blastoff occurs when this code is not run, and this happens because of a check:
That last bcs can branch PAST the above code, therefore NOT running it and NOT properly placing Yoshi's Y coordinate. Because of this, and because address $700058 is written to elsewhere for completely different purposes, most if not all of the time you will get something like these values (taken from an actual trace):
Because $700058 was not properly computed (because the code was was branched past), it gets this 'garbage' value of $0001 which it never would normally get. Because of this, our formula to move Yoshi goes like this:
This comes out to $FFE9, or -23! Now we are moving 23 pixels BACKWARDS, or in this case up, each frame. Which of course causes Yoshi to blast off to the moon.
So what causes this branch to go past the necessary code? That code simply checks to make sure Yoshi's X coordinate is within range of his shell. In brief, if Yoshi's X moves off the shell, he blasts off. Normally, this wouldn't happen, but it can if you ground pound him early because that would bypass AI states which zero out his X velocity (the process of him landing after falling, etc.), therefore he can retain his X velocity and keep moving left or right, while Yoshi stays stationary. This causes Yoshi to be outside the X bounds of his shell, which causes the check to branch past the necessary code.