This is really clean, nicely done!
I'm probably not very good at the game, but a couple levels felt a little unfair with how tight the movements had to be (the last corridor in level 2 stuck out). On the whole it felt nice though, and could be even better if you really juiced it up.
Some small QoL changes I'd suggest:
- Some of the elements could use a bit more distinguishing, the red gate vs the red goal, for instance
- Some extra space surrounding the level itself could be handy? I found I had a hard time navigating when I got near an edge (the bottom-left corner of level 4 is where I ended up giving up), and having a bit of extra space for move your mouse around in could be a big help for that.
- Having the level only start once you grab the orange cube would be a nice touch. I often died before I could actually grab the cube because I was trying to look at what the level looked like, or my mouse was too far away from the spawnpoint when I restarted.