Draw patterns in your very own little sandbox with this magic magnet Zen garden set. It has a raised sand tray that sits in a frame that can optionally hold a pattern plate below. It uses two 5mm diameter ball magnets - one that sits in the sandbox above, and one in the stylus that is used to drag the first ball around from below. If using a pattern plate, just drag the stylus along pattern groove and the ball above will dutifully follow. Or you can draw freehand without any pattern plate.

I've included two pattern plate files - a swirly petal pattern and a square pattern. I've also included a blank pattern plate that can be customized with your own design. The grooves in the pattern plate should be 5.4mm wide by 2mm deep.

Lastly, I've included a screed that can be used to level the sand. It has two different depths for creating different effects. With the sand shallow (about 2.5mm deep), the ball is exposed and you can create crisper figures. With the sand deeper at a little over 5mm, the sand covers the ball, which roams beneath the surface like an Arrakis sandworm. This leaves a more subtle pattern.

CAUTION: Small magnets, ball or otherwise, are an extreme ingestion hazard. Keep all magnets away from small children who might be tempted to eat them.

Printing
I printed this in PLA with 0.2mm layers. It prints with no supports, but I would recommend using a brim on the frame, as the contact surface with the bed is pretty thin.

Assembly & Use
First use a drop of superglue to glue one of the 5mm ball magnets into the tip of the stylus. Then just place one of the pattern plates in the frame, pattern-side down, and then place the sandbox tray on top of that. Fill the sandbox with very fine sand.

Now, just drop the other magnet into the sand and reach in below it with the magnet end of the stylus. The balls should lock together through the bottom of the tray and through the pattern plate. Move the stylus into the pattern groove to keep everything from moving around. Now you can use the screed to level the sand, working around the ball. Add or remove sand as needed. You are now ready to trace away!