The aim is to guide a ball bearing/glass marble through the maze inside the ball. An extra flat surface has been applied to the bottom so that you can determine which is the entry side and the exit side (ball can travel both ways) and to place the ball somewhere without rolling away. Channels are square and rotated 90° so that the walls are at 45° angles. Overhang shouldn't be a problem (use no support inside). Channels are square 10+mm, it is best to use a ball bearing/glass marble of about 8mm when printing at 100%. Orientation for printing is the flattened side on the bed, with support for the lower part of the sphere and the central hole.

Scaling allows the use of a bigger or smaller ball bearing/glass marble.

p.s. by using a semi transparent PLA the maze will be less difficult.

Update 12-09: printed both on FDM and SLA printer at 60%. Used a printed bal of 5mm. Worked really well! The FDM (orange) printed ball was very difficult due to the fact that you can't see the bal. The SLA printed version is translucent, so you can track the movement.

The added hollowed out version needs no support for the central hole. Try with no support inside.