Dunno. I haven't played it a long time, so I don't really remember any of the details besides that occasional review snippet that gets displayed on the downloads page, where I mention "vertical spaces."

JJ1 level design is a constant battle between speed and resolution, and pretty much every single tile needs to be placed with those in mind, so I do what I can to make the challenge reasonable. I place strings of pickups at the tops of pits that are safe to fall down, if they look like they might be ambiguous, or have bushes (or whatever) sticking up from the ground below that stick into your visible screen. If there are enemies or spikes below, I try to make them close enough that you can see them while crouching. If you're supposed to jump over a pit, there may be a string of pickups in an arc above it. If you've been going through a fast area of the level, I try to place something that obviously slows you down without hurting you—a short wall to climb over, a pit to fall down, a visible platform to jump onto in advance, or even a little warning sign in the background—before you reach the actual danger. If a type of obstacle occurs more than once, generally the first time you see it is the easiest, to give you a chance to learn how it works before it gets more complicated. If there's an obstacle or enemy that's only visible part of the time, like the fire monsters in Marbelara, I may try to include common visual cues for each part of the level it appears in, which exceptionally attentive players can pick up on. I bear in mind a general principle of Sonic-themed level design that the lower down you are the more likely you are to get hurt, so I hope other people know this too, and mark your height with visual cues like caves or background mountains vs. clouds or stars. If an enemy or obstacle is going to shoot at you, I make the bullets infrequent enough that you can probably see it coming first and kill it/get out of the way.

All that said, it's not like I want everyone to blaze through every level on Turbo without taking a scratch. There are plenty of obstacles that will likely hurt you even if you do know they're there, and that's good. All the above paragraph is about trying to ensure that every time you get hurt, you feel like it's your fault, not mine. And no matter what I do, there will always be people who rush in where angels refuse to tread, or simply disagree with me about what feels like a dangerous area and what feels like a safe one.

So... we'll see!