Okay, since I assume the park/nooks levels are correct, I tackled the rest:
> A level that "talked about the Marble's life". It broke the 100 gem count. Maybe speedran by Imperial. I got under 2 minutes.
Marble Timeline by Kurt. Level desc: "Explore the Marble's Life". It had
99 gems in it, not 100.
Correct.
> 1 gravity level. In space.
Ender's Level by Bodie. I'm guessing that one because well, space and gravity being the keywords.
Other possibilities which may or may not be what you want, but they contain the gravity code (they're all MBG except last one):
The Dark Side of the Moon by Lonestar
Dr. evils gravity space zone by Luke
Enterprise by Pablo
Falling Up! by Robot-Marble
Gravity Experiments by Whirligig
Level Competition 2: Gravity Shortcuts by Ian
Marblaxia\'s Rocket (Part 1) by Henry
The Moon by Lonestar
Jupiter by Ian (MBP)
> Pitch black level with 15 gems and a tube.
No level containig 15 gems and is a pitch black level exists.
Need more info.
The only light visible is your marble effect light? Tube is narrow and uses the MBG Blue scaled, probably 0.5 1 4... to get to the end.
> Small level that took Learning to Roll and screwed it up by making it at least moderately hard.
> Big level that resembled Learning to Roll, but... just had lots of challenges between the middle part.
A few choices here:
Escape: Learning to Roll by smellysock
Learning to Roll: The Hard Way! by Golden Marble
Mega Pipe.mis (has learning to roll interior and a lot of other stuff, didn't play so I'm throwing it out here)
Learning to Roll... or not. by Lonestar
Bumper hitting by Matthew
Hut at the top. This is the only one where I'm not sure if I made the three gems. I may have used another .dif.
...I checked Orbz. This is probably another arrangement of .difs from me.
The narration felt like the marble "would never pass these" and it felt like a level in a sort of series.
It brought you straight, with skyscraper graphics that were sideways, blue and purple. Sky was pretty dark (or was it interiors blocking the sky?) and perhaps meant to give a space look. The U-Turn lead to an entrance in the wall, heading left relative to the spawn.
The level before that was hidden in black space interiors, being narrow and giving room to challenges if need be.
Meanwhile since your memory got the 99/100 gems level wrong, I went ahead and searched into all levels containing 99+ levels.
Levels with 99 gems:
Space Ramp Madness II: The Revenge! by Nikko (MBP)
Dive to Dooooooom!!!!! by Wyatt & Totodile (MBP)
Marble Timeline by Kurt (MBG)
Speed Demon by marbleman (MBG)
#4 Mission Impossible by Keman (MBG)
Levels with 100 or more gems:
Catch That Marble by Henry (100 gems - MBG)
Lumberjack by Robot-Marble (105 gems - MBG)
Core by Henry (184 gems - MBP)
Jump, jump, jump, JUMP, to the moon! by Andrew Patterson (200 gems - MBG)
Luke's level 6 by Luke (240 gems - MBG)
(The sole premise of me using TubeTwist's up to 24 numbers as replacement files. Except, you know, the missing '0.png'."
And first place goes to:
A CHEVY LEVEL - BY KURT by Kurt (1091 gems - MBG)
... what the crap.
Hopefully you don't get so many gems at a time it breaks your sound card.
To clear out some, I'm going to download Orbz and any other old Torque Game Engine games to see if I can take up the .difs.
> Wouldn't you know it. I go on Orbz screenshots and immediately see the .dif I used for Advanced Level 2(?).
static.garagegames.com/static/pg/productpages/orbz/screens/thumb_product_screenshot_orbz_10.jpg