Thank you so much for your feedback! And don't worry about sounding to negative, I'm a big fan of constructive criticism. And I agree to pretty much all of your points. The good news is, we're still pretty hyped about working on the game, so there's a very good chance there will be a post-jam version of this game that will adress some of the issues.
For point 2 and 3, the lazy excuse is time limitations. The original design was to make the egg fall and break when there was no floor directly beneath it, but we didn't find time to implement it. Currently, we actually do like the egg staying in mid-air for gameplay reasons, as it's one less thing to worry about, but we want to give it some cute little wings to better indicate that and change it so the bunny can only collect the egg while they're actually on the ground.
We're also already working on adding some relatively simple but tight introductory levels to help the player build up an arsenal of solving techniques. But yeah, as it turns out, having a huge possibility space by default does tend to lead to pretty lenient level design. Definitely a challenge that will remain for some time.
The first point is probably the most tricky one. We do plan to add an option screen where you can change mouse sensitivity (and the backbone for that is already written), but I'm not sure it's enough to fix the underlying issue. A few other ideas would be changing the camera to orbit controls, which I'm a bit hesitant about because it would break the cube's symmetry, and/or adding further control elements to rotate the front face clockwise or counterclockwise, which would probably help a little bit but would also add additional screen clutter. If you have any more ideas, feel free to let us know :)
Anyways, sorry for rambling on for so long. I'm glad you enjoyed the game overall and who knows, maybe we'll play each other's games as full versions one day!