Thank you very much for your comprehensive feedback!
The video made me realize that indeed beyond 3000m there is nothing!
I've just checked the code and yes... I had deactivated the change of bottom ore to do the tests and I never reactivated it...
Thanks again for your time, you have an extra subscriber in Youtube!
I'll soon be releasing an alpha of the game I developed at last year's game jam. In one year it has evolved enormously, and if you're interested I'll be able to give you a version. Your feedback will be a great help!
Thanks again for your time!