Hi, I just played all eight levels the game has to offer, and while this game has plenty of issues that need ironing out, I'd like to first say that I love the concept of this game, with level 8 being the one that showed me the potential this game could have, being a strange mixture of snooker and puzzles.
First thing's first, the menus. While they do the job they could use a tad more polish, like the marbles on the level select also being clickable to start the level, the ability to go back to the main menu without having to quit the game first, and the in-game white boxes need something more, it seems rushed and I think a simply white box with black text just seems lazy.
Next of all the controls... well that depends on the level. One level I was stuck in the same place like a turret, another I have 3d movement, then only camera movement with the mouse. There needs to be reliable controls that don't keep switching around every level. I'd suggest the 3d movement from level 8, it gives freedom which would work well.
Then comes the gameplay... and this is the oddest part for me. So some levels are very simple, just shoot marbles at other ones to get them off a simple platform, and these vary too, likely not by design. The first few were fine, they work well and is a good tutorial example but then level 5 happened. Around 20 tiny marbles on a single platform and 15 minutes to knock them all off. Though for whatever reason the tiny marbles had incorrect collision, they only moved when you got a pixel-perfect strike in the center, both marbles need to overlap. I still did this on my first attempt but it took far longer than I would have liked, and the lack of timer in that stage made me wonder if the time limit existed at all.
In my opinion, the stages need to be overhauled to be more like stage 8, you'd want to get marbles from A to B, and your only tools are the stage itself and carefully aimed marbles. It has the potential to be a slow yet strategic puzzle game where you can line up your shot and watch as carefully planned bounces off walls get the marble to wherever you want.
If you'd prefer a more action-focused game I'd suggest reducing the auto-fire rate of the marbles and fix this issue where each shot moves your character a bit, as I wildly vibrate whenever I shoot a lot of marbles at once.
If you want more help with playtesting or help improving this game let me know, I'm interested in seeing where you take this project.