My issue with maze games and all "find key to unlock door"-type games is that they are boring.
I understand that you don't want to add TOO many new features since you have a niche audience already that likes what you do, but there's no plot, there isn't really a "puzzle" element (I don't consider mazes, even cool, 3D ones, to be puzzles).
You added the 'color chaos' this time around, which conceptually is a good idea but in practice just makes me run into dead ends more often than the previous versions due to having the wrong color, and having to backtrack.
You could have more texture or at least changing colors every level for your background. The red gets a bit monotonous. Having "wall-hit" feedback is a good easy way of adding polish. If you search up "neon maze" you'll note that there is a little shock when the pointer hits a wall. Other 'power-ups' or 'gimmicks' might include something to increase your speed, or a "layer viewer". The "layer map" you have as a bar on the right-hand side could be polished to be more than a dot and lines. You could add gradient lighting or just "lighting" to the stage to make it look more dynamic.
A personal tic of mine is the timer. I wish there was a way to turn it off like I can turn off the music and sound, because it just stresses me out. Mazes for me are about getting through, not necessarily about being timed. It's useful to be able to look up my time, but the reminder that time is passing makes me frenetic.
The bonus stars don't have a "bonus" feel. They could light up before disappearing, or fade out, or SOMETHING, but as with every item you pick up, the item simply disappears from the map and appears in your bar. No animation whatsover. Even something really subtle could add to the polish of the game.
Overall I love the concept of a 3D maze, but it seems like you didn't try to make the maze polished and go that extra mile for presentation. Additionally (and again I'm aware this is personal preference) I wish there were more gimmicks and puzzles.
For gimmicks: rotating the layers above and below might be cool. Having another ball mirror your movements and potentially block you could be cool. Plot would be cool. "Dark" floors you have to light up could be cool. Easter eggs could be cool.