OpenScad Marble run experiment 2

Another marble run experiment. No higher mathematics is used, but it takes long time to render (>2h) and to print > 20 h, 0.15 mm, 0.4 mm nozzle.
I designed it for 8 mm steel marbles, but the slope is too low for this marble size. 10mm marbles were working: https://youtu.be/vDOTx4EiRcI

I ran out of the the blue filament so the last layers were printed with another color (filament change at 5 o'clock in the morning)