After printing and assembling the heart base, I had to figure out the best way to line up the heart pieces. I decided to make a little divider for the interior of the heart to help separate the pieces. Now, each piece has its own little recess to fit into!

The blue piece is the heart piece that I modeled and printed. There are two little nubs coming off the top to allow you to grip the piece and remove it. The grey tape is to cover the magnets and hold them better in place. The magnets line up perfectly with the magnets in the heart base! The LED in the middle of the piece has an extrusion coming off the top to hold the spring contacts in place. I put a dab on hot glue on top of the contacts to hold them in place.

I found these super awesome LEDs from Lighthouse LEDs that include resistors in the LED!!! Using these will save space by removing the need for a resistor on the anode leg of the LED. I think they lend to a much cleaner, simpler design as well.

When powered up, the pins make proper contact with the spring contacts and the LED lights up!

This is the best part of the whole thing. The magnets perfectly align the heart piece in the base! If the piece is not quite lined up, the magnets will snap the piece into place. I made sure to sufficiently distance the magnets in the base and the piece. There's enough force between the magnets to secure the piece, yet make it easy to remove the piece.

Now that I have the first piece printed out and tested, I would like to slightly change the location of the magnets in the base/pieces.

My next step will be modeling and printing out the rest of the pieces, so stay tuned!