Okay, time for my own feedback. First a few general things:
- I find it odd that you didn't make your levels accessible in level select, especially since some of them are skipped when you start a new game. The only way to reach the incomplete levels is to warp to them via the map command. That's not very user-friendly.
- 95% of all statistics are made up on the spot. Giving percentages for the progress on your levels is very unprofessional since you never know exactly how far you are in. It's better to describe the status of your levels in words, e.g. "IFZ1: Finished except for an alternate path" or "RHZ2: Only the first room has been started".
- If your levels use asset pack textures, then include said textures in your pack and give proper credit. Forcing players to download and add the asset pack manually is not user-friendly.
- Don't do too many things at once. I see that you have already started a few other levels. Please don't try to make them all simultaneously. Concentrate on one level at a time and try to make it as good as you can before you start with other levels.
Okay, now for the levels.
RHZ1:
The whole level is very flat and empty. That means that a.) there's very little to do aside from running forward, which makes it boring, and b.) there's very little exploration to do. There are a few secrets, which is of course good, but they're all blindingly obvious because the terrain is so basic that every little detail stands out. Another problem was that the ceilings are frequently too low, which makes the rooms unnecessarily constrictive and has the undesired side effect of invisible walls where the thok barrier is. Take a look at the room heights in GFZ1 and use similar heights in your level. The ceiling should be always a good bit out of reach.
What makes the problem with the invisible walls worse is that your design is very "room-y", for the lack of a better term. Take a look at GFZ1 and GFZ2 (and to a lesser extent, ACZ1), which have a very open design where the terrain between rooms is frequently used as extra territory. Your level consists of a few basic rooms that are connected by corridors. It's important to avoid transitional corridors as much as you can because they tend to be boring. The large corridor in the middle of THZ1 is one of the worst pieces of level design in all of SRB2. Another minor thing: Please don't use GFZFLR02 and GRASS3 in the same level. They clash horribly.
Most of the level can be beaten without jumping at all, which is obviously a problem in a platforming game. To make a stage fun, it's important to challenge the player. Of course, in a first level, these challenges should be basic and easy, but they nevertheless need to be there. You did include a few challenges, but they hardly do what they're supposed to. I actually have to try to get hit by your single lines of spikes. Please make them thicker, like the ones in GFZ1, so that there's an actual threat of getting hit by them. I also remember a pit with a few safety platforms in it. Aside from the fact that a first level should never have any death pits (the first death pits in SRB2 2.1 are in DSZ2, which is the eighth level out of twenty-one), it's also easily skippable because one jump clears the whole pit. That makes all the safety platforms obsolete.
IFZ1:
The first half of this level has the same problems as RHZ1: There's nothing to do except running. At least the ceiling heights are more reasonable here. Also, if you want to make an alternate path and it's not done yet, don't seal it off with a striped wall. Just remove the entrance to it outright so that players aren't stumped by a sudden dead end and don't even notice that something is missing.
The entrance to the factory shows some actual detailing, although rudimentary, which is nice. I really have to wonder why the fences are intangible though. When I see a fence that is higher than my player character, I except it to be solid. The rest of the factory shows some attempts at actual platforming, most of which are okay. The turret at the end seems pretty superfluous though and the ceiling is again way too low.
Bottom line:
RHZ1 has no real redeeming value. The best thing would be to completely scrap it and redesign it from scratch. This time, ask yourself what challenges you want to pose to the player before you start mapping. The second half of IFZ1, although it's pretty much a second-rate THZ2 clone, is okay and you can keep it if you want to. The first half is garbage though and needs to be scrapped and redone.
