Modular heart shaped box with a swivel hinge. Stack as many layers as you like in as many colours as you like!
Print a lid and as many boxes as you like. There is also an optional base (if you want to cover the bottom hinge hole). Print out connectors and clip it all together. Works very nicely and makes a good Valentine gift box.
The swivel hinge mechanism uses Pin Connectors V3 by Emmett and they work really well. You can use this design to make stackable boxes of any shape e.g. animals. I found that for an 8mm radius hole, a 7mm radius pin works well.
I printed this half size with a 1.2mm wall and 50% infill because I am a bit low on red and pink plastic. Prints out OK at 1/2 size, but the walls are a bit thin. Printing at 0.75 size with 100% infill or full size with 50% infill would have been better.
I printed in PLA in a nice red I got from Ultimaker and Cherry Blossom Pink from Faberdashery.