All of the jam feedback I've given other games has been based on the builds that were available when the jam ended. Unfortunately, at that time, Cube Slide was still missing its _Data folder, so I'm going to give some very thoughts on the updated build I played afterward.
First up, I enjoyed what I played. There isn't a huge amount of game here, but it feels like it could be a good starting point for something larger.
As I mentioned on judges' round table video, I feel like some enforcement of pacing (a minimum speed and preventing backwards movement) would make the game feel more whole, and either some rails or resistance on the sides of the level might go towards helping round the game out.
Tiny bumps/scrapes counting as being on par with head-on collisions feels a bit off to me. I'd experiment with either ignoring impacts which don't impart more than a certain threshold of movement onto blocks, or make the player cube get larger every time there is a collision, giving some leeway for small mistakes, but also providing some disincentive (the larger the cube, the harder it is to navigate the gaps between blocks).
I had to give +x permissions to the game executable for this one. Typically, for Windows based developers, this is difficult to have control over, but if you're on Linux or MacOS, setting executable permissions with the "chmod" command on the game binary before zipping up the files will make sure that that's good to go on users' computers after they download and extract them.
Thanks for submitting, and best of luck with the project if you continue development! :D