I didn't have time to go through the whole thing again, so I'm going to provide feedback up to the third chamber. Generally, great pacing in terms of difficulty and action. I never felt overwhelmed by the game at any point. The detailing and transitions were immersive and felt consistent to the game world. The puzzles were fun to solve. The biggest issues the level has are of readability and accessibility. Mind you I think you have already gone well beyond the average modder in this respect, but if you improve in this area, you will close the gap between amateur level design and professional. I can already tell you have a good design perspective and think as a potential player rather than yourself. I would just apply that line of thinking to every aspect of the level.
Feedback in spoiler tags
||Polish feedback
Some of these will seem nitpicky, but that's because you don't have many major issues. Besides, recognizing and fixing small things separates the great from the good. These are things that a player may not inherently notice individually, but can sense in the quality overall.

The stairs that come up cuts off half the path unexpectedly. I think it would be better to just push the stairs back a little, or you can try to trigger the stairs to rise earlier.

The composition here is a bit weird. The two cameras share a lot of the same space in their viewing arcs. The inset lights are lighting a space that wouldn't logically need lighting (too high up). It didn't bother me too much, but I would disable the cameras to fit the visual theme.

It looks like you can make this jump, but its actually not as easy as it seems. I don't think there is a good reason why it cannot be closer like the jump from the other side.

I want to inspect the button in the distance and the space around it. The angle I have into that space is unnecessarily small. I would love for it to open up a bit more. I understand I can just portal there, but being able to analyze the space from one spot helps spatial awareness. The button itself could also stand out more.

I had to use a pretty advanced move to see what's hiding in the corner. If I had not done that, I would have to rely on the fact that there was something I must do over there, because you built it. That makes the player aware that there is a designer that is stringing you along. It's less satisfying to solve a puzzle by trusting that each white panel serves a purpose, than to just see the puzzle piece itself and understand why you would go there. Make the player want to do something instead of forcing him to do it.


To move the cube back, you have to shoot the portal from the first angle, and move to the second angle to see where its going. There isn't a whole lot of space to work with here. It's hard to tell that the cube would either fall into the slime or be emancipated unless you remember the layout of the level. Let the player have a better view so that he can shoot and watch the cube from the same spot. Then, you wouldn't need more room to maneuver in the first place. Yes, the button is right there, so the player can just hit it again, but players are unpredictable. They might get themselves into a situation where they have to repeat parts of the puzzle.

I loved this right here. You forced the player to drop directly into a tractor beam from a transition area. Not only is it interesting, but it also tells the player that there is a tractor beam in the chamber immediately. Jumping off the beam also lines you right up to the exit door. Perfect.

The faith plate kind of blends into the tiles. It's easy to accidentally walk over it without even seeing it and die. I would separate or indicate it visually.

The tilting of the panels here seem really artificial. The flatness of the textures don't help either.

Here is another readability issue. I could almost see the button. It's teasing, since there is a window, but you can't see what's inside. Again, the player has to trust you and just go there. I would show the player what's inside from this angle.

Another readability issue. I have to go onto the very edge of the platform, risking falling off in order to see the super buttons. The angle I have to see them at is very steep as well, making it feel "neck-straining"

Great work here. The cube drops into tractor beam as long as the beam is used to cross the slime. Catching a cube with the tractor has been done so many times, that it really isn't interesting as a puzzle without some kind of twist.

Good stuff again here. The window allows the player to see the space outside, but prevents him from taking the cube out. Great solution to visibility issues of the laser field.

This is an unnecessarily obscure and tiny target to hit. Artificial difficulty is an outdated design philosophy.

I can see 14 signs from here. Holy bananas. This is confusing. I'm not sure how you can fix this, but I would fix it.
Puzzle design feedback
I had a lot of fatigue from playing with lasers in chamber three, and to my dismay, there were lasers again in chamber four. Honestly, lasers are just one of those mechanics that induce a bit of mental stress, but that doesn't mean you can't help as a designer to prevent that.
The detailed transitions did a great job of making feel I am progressing in the game. Very rewarding.
I love that you used stages to your more complex puzzles, so that you don't have to solve it all at once. While daisy-chained puzzles are interesting because it tests your memory, it is frustrating when you fail accidentally and have to repeat steps.
Unless you're specifically targeting a hardcore audience, I would love to see more subtle guidance in the level like spotlighting, contrast in visuals, well-timed music or stingers, etc that help the player solve the puzzle with an invisible hand.
The puzzles all focus on the traversing of space, which is what Portal is all about. Great job there. I dislike puzzles that focus on timing, accuracy, type-matching, because they feel out of place in the game world. These things can complement the core-gameplay but should not be the driving playstyle.
For the most part, uniqueness is a very important factor in puzzle design because the satisfaction of puzzles come from the solution. While Portal tried to augment that with funny dialog, flying through the air with plates, and killing turrets, it still was not enough to overcome boredom from repetition. Playing any level twice is not really all that fun, which is not true for lots of other games. Repetition is a killer more so in puzzle games than any other genre. I think you achieved a good amount of uniqueness. If you have more time, I would add something epic to not only give the level even more uniqueness but ties the chambers together. For example, shutting down GladDos with the lasers was a great oomph to the behind the scenes part of the campaign.||