The visual effects of this case work well and the movements of the coloured powder in the liquid are very smooth. Something like this packed into a small case would lead me to believe that it does not move much but there is enough space to allow lots of snazzy effects and a very coordinated sprinkle. The powder doesn't seem to go everywhere either and accurately responds to the tilt you apply and will fall bottom first and not all at once.
The design means that the case adds thickness to the phone which may not be a problem to some but I keep my phone in my pocket which becomes more noticable. The thickness is not too bad though given that it holds liquid and moving parts. What I did find was that if you apply pressure you can interact with the moving powder but for some reason I had a section of powder that stuck and wouldnt move with the rest (check picture). After leaving the case for a while it went back to normal so I would recommend avoiding pressure to the back.
The buttons match and function well and the protection to the back of the phone is great. At the front there is a decent lip that will protect the screen from small falls.