My Challenge to Make a Marble Run Machine - An Ant's Nest

I've finished making one of the parts of my marble run machine.

 

I call it an ant's nest. It has a long twisting ditch that balls can roll down and looks like an ant's nest.

Making the ditch, I used a ball-shaped bit. This bit was good for making a ditch for balls. Adjusting the depth of bits can make a long hole so the balls don't drop off and can be seen outside.
 

However, there was one thing I had to be careful about. The edge of the ditch would become sharp and easy to be damaged. Therefore, I drilled a hole with an ordinary bit that was a narrow diameter than the balls first, then a ball-shaped bit to prevent cracking.

Firstly, I made a trial version of the ant's nest with MDF. It worked well, but I wanted to be more fond of the shape of the ditch. Therefore, I changed the shape of the ditch.

Here is the one I made in the end.

The balls roll well, but I wanted the last curve to be more gentle if I could because they run too fast when they come out of the ant's nest.

After passing by the ant's nest, the balls go to a trumpet-shaped tray. The balls jumped out of the tray about one in ten times, so I prepared the second tray. The second tray has a height of 15 mm, enough to prevent the balls from jumping over. The balls that go into the tray rotate well, and it's fun to watch.

I've finished making parts of nearly half of the marble run machine at this stage. I thought I'd spent lots of time, yet it's still only half done. How long will it take to be finished?
There is still a long way to go.