So, being greeted with a big EULA right at the start is not something I'm used to for a jam game. I did read through it, and it seems to be typical CYA legalese. Of course, "agreeing" to EULAs and T&C is also considered to be one of the most commonly told lies in the world, so plenty will just click and play without reading. I will say that starting a jam game and seeing something like this would generally have me just stop there and move on, as most jam games aren't really worth "agreeing" to random EULAs. Between our past interactions and this being a submission to our jam I am willing to take the time to read through it, but it is something to consider. Of course, these days people are crazy sue happy and adding something like this to protect yourself is understandable.
In the intro text, the edges are being clipped. The left edge is most notable.
The intro story has me questioning who your character is, who you are dealing with, and if this is a bad deal to agree to.
When you are close to an interactable object it shows text telling you to press E to interact, but if you cannot interact, then nothing happens. There should be some form of player feedback that you can't currently interact. Either the text saying you can/lack the required item to interact, or even a negative sound when you try to convey that the key press did nothing. I know this is in an early state and may be on the list of things to deal with, but still want to point out the things I notice.
3D platformers are not really my thing. I often find I have a hard time translating the camera view into real world positioning that my brain can process well for judging where edges are and when to jump. In this game, I think the platform textures could use with additional texturing/shading to give more definition, and help judge distances. As bad as I normally find 3D games, the fairly plain surfaces made it harder to judge. I will say that the background was good and allowed enough contrast that adjusting the camera I was able to get enough detail to make some progress.
I made it through the green zone, but it took several tries and was a challenge. I almost lost when going down an angled platform and it suddenly had me doing small hops, right before reaching the edge. I landed just before going over and was able to make the jump to the next platform.
I used W, and sometimes S for movement, and the mouse for almost all rotation/direction changes, except when testing the controls. The mouse being able to adjust your direction was helpful in landing some jumps where it was hard to judge the next platform exactly from the previous one, as I could respond faster, and by just the right amount, with it.
I did try your other movement test. The inertia/friction on it made it feel like the PC was running on ice or oil. That would not be fun to play, at least for me. I also had trouble getting it to release the mouse cursor and ended up using keyboard shortcuts to close the tab to exit.
I tried the blue level and got to about 4 platforms from the end. With more attempts, and slowing down a bit to do more estimating distances at the end, I'm sure I could make it. However, it is really taking a lot to focus on the edges and timing things, and I'm not up for more right now. One of the kids has already played, and they got further, so will be able to provide some feedback on later levels.
The slope movement definitely needs work. Those hops are very problematic. I don't do much with 3D, so don't know enough to be sure about might fix it. I have some thoughts, and maybe they will translate into something that can help. My take on the issue is that as you are running down a hill your forward velocity is greater than the gravity pulling you down, resulting in you being off the ground, which is causing your character to switch to a jumping/falling/in air state. Obviously, messing with the overall gravity would affect the feel of the game and be a pain to balance properly. Maybe you could do a local increase in gravity on the sloped platforms, but even that would mess with timing. I'm not sure if the 3D models can be refined to fix the issue. With this in mind, my "fix" would be to add some logic to the checks for if you are in the air to consider if you just pressed the jump button to start leaving the ground, and if not, check if you are a short distance above the ground, probably with a Ray Cast. If you did not jump, and are above ground, and the distance is small enough, then treat it like being on solid ground. You could also limit this to only trigger if the ground is marked as a slope, and even based on travel direction being downhill. Maybe also add some logic to adjust the position so you actually are on the ground. This could be a manual calculation of the Z position so the player stays touching the ground, or possibly increasing the gravity a small amount for a short time, maybe a single frame at a time, to pull the character down. Again, 3D is not my thing, so my thinking here could be completely off, but maybe something in it can be a seed for something that will work.
This seems like a good start. There is already a bit of story, even in its early state. They layout of starting from a central location and going out to each zone to get the next key works. The music fits the game. The geometric platforms work for the game style. It is a challenge, but I was able to complete the first level without too many retries. I can't speak to later levels or level progression, but it was decent. It may be a bit tough for a first level, and you may want to start things off with more of a tutorial/training level, but it wasn't so difficult that I gave up before finishing it.