[FREE] Music visualizer with 3D-effects, space journeys and tunnels

We have released this music visualizer:

https://play.google.com/store/apps/details?id=astral.teffexf&hl=sv

12 3D-worlds are included and you can press play on any of them to start the music visualizing. There were some bugs before, but I hope that we have fixed the important ones now.

I am interested in opinions on our approach to the in app purchase and how the free version works. We have included one free song. The users have to upgrade to premium if they want to visualize their own music or streaming music. Do you think this is a good approach?

We have thought about other approaches to this also, like a time limited trial version. It would be possible to listen to all music during this trial. Do you think that this would be a better approach?

Another approach would be to only have a few visual effects included for music visualization in the free version, but the full version would have all. All the visual effects would however be included with no music in the free version.

Or do you have any other ideas or suggestions about this?