Thanks a lot for your feedback.
I'm currently working on the polished version and added indicators with timers to show when they will be executed, as well as some particles and sound effects.
Also when a cube comes to a full hold you often need a very high velocity input (orange or red) to get it moving again.
I actually finished all mechanics, fixed (hopefully) all bugs and added polish. Now I will just make some levels and a menu and then upload the revised version.