Thanks Jack, but I decided to go in (yet) another direction with my hack, back toward the idea of making a harder game through gameplay tweaks, rather than level design. SMW Customizer really helped with this, as did carefully perusing the ROM map (to find what address did what).
There is still one issue I have left to resolve, before I'll release my hack: how on Earth do you eliminate the annoying once-every-four-frames "flicker" where the bottom half of the player sprite mirrors itself, causing a rather jarring "broken-tail" effect on my Mewtwo sprite? I've searched VERY thoroughly through the ROM map, and there are numerous entries concerning the overworld and its sprites--but not a single one dealing with how to stop the player sprite's overworld idle animation. That's what I want to do...so, of course, there is NOTHING at all concerning what I need to do.
I did find a 384-byte block (that is a TON of addresses to sift through!), dealing with Mario/Luigi's overworld sprite animations, in general, but I don't have a clue as to which ones deal with their idle animations. It would be cool if I could make it look like Mewtwo's bobbing up and down (via psychic levitation) while idle, but if I have to, I'll simply settle for making him stand still.
I would greatly appreciate it if this question is answered with utmost promptness. I'm at my wits' end trying to wrestle this hack into complete obedience. It's about 99 percent of the way there (just those annoying overworld-sprite flickering issues to deal with), but 99 percent is not 100 percent, so I still won't release my hack until EVERYTHING is debugged (or I find a way around the bugs I can't get rid of--so I can tell everyone else to do the same).
I take pride in my work, and I do NOT want to be known as "that lazy hacker". Sure, this is my first hack ever, but I want it to be a good one, and one that everyone will enjoy, because of its challenging but far-from-unfair difficulty.
The intro says it all:
"Mario sent ME to destroy you, Bowser! I am the Ultimate Pokemon, and when I find you, you will DIE! I...AM...GOD! -Mewtwo"
Here are a few tips to avoid some minor bugs I couldn't get rid of:
Mewtwo may get stuck inside a red running block (those triangles you can run up). This isn't a problem, as it won't hurt him; simply float either backward or up, and he'll become unstuck. Besides, he doesn't need these due to the free-scrolling feature I built into the game.
Also, during the Iggy/Larry battles, avoid getting hit by the orange balls at all costs--if you do get hit, while standing on the teetering platform, you'll teleport to some random place, which could end up being in the lava, way up in the air, or even INSIDE Iggy/Larry! the worst that can happen, though, is you simply lose a life.
One final bug I've found, is that in very rare cases, the clipping protection I've built into the ASM code giving Mewtwo psychic flight may still fail, but only in one level (that I've seen so far): Chocolate Island 4. This is due to the rather oddly angled ground in some places, where if Mewtwo flies forward, he'll simply pass INTO the wall, but be unharmed, due to the "hollow" nature of the wall.
Here's a brief synopsis of the changes I've made to the game:
1ups don't give you an extra life anymore--they are simply another way to get the Tail Whip powerup.
Starmen give you the Psystrike powerup (rapid-fire Yoshi Fireballs).
Red mushrooms are like the green ones--they give you the Tail Whip powerup, as do Feathers.
Fire Flowers retain their default properties (they give you Psystrike--this game's version of fireballs).
Also, collecting coins to gain 1up won't work anymore, and the Bonus Game has been disabled. These tweaks will make extra lives much more difficult to come by. Yoshi coins, getting 50 on the Goal Tape (3up), 1up moons, collecting silver coins from hitting a silver P-switch, and chaining enemy stomps will be your only methods of gaining extra lives. MAKE THEM COUNT!
Also, the timer will countdown one-third faster than normal, and many enemies will move and recover 50 percent faster than normal (Pokeys move at TRIPLE their normal speed, so you'd better brush up on your Yoshi-tongue-aiming skills!) Chucks now take 5 hits to defeat by head-stomp. Boos will still keep coming if you turn to face them. Classic Piranha Plants will still come out of their pipes if you stand next to them.
Yes, Bowser prepared very well for Mewtwo's arrival. Can the psychic cat overcome the odds and defeat an even tougher Koopa army, or will he fall prey to Bowser's twisted schemes? It's up to YOU to decide!
"Let's-a go!" --Mewtwo, in a badly-done Mario impression
The meaning of life is 42 because potato.
I don't feed trolls. I feed THEM to Cthulhu. He finds them DELICIOUS.