This has become one of my favourite designs, as it can be used for birthdays Valentine's day, as a voucher, ... So it is really universal. The idea is to pack a chocolate bar in the box and display the letters "du" in German or the letter "u" in English through a heart-shaped window. I used duplo as a chcolate bar here, as it works as well in German as in English. And in between it is available worldwide, also not yet common and therefore a little bit difficult to get in the US. But of course you could do the same with any other chocolate bar that has a "u" in the name and where the letters are well known.
Carefully measure the chocolate bar and build a box that is only 1mm bigger in every dimension, so the chocolate bar will not really shift in the box.
I designed it in a way that in each corner of the box I have a 4mm x 4mm x 4mm pin left that will hold the top plate later. This way you can glue the bottom parts and the top plate is hold in place by these pins.
If you want to use my design for duplo you can choose wether you want the version with the additional star or without (see the project photo for the comparison). Each of them is on a different canvas. You will need all the parts, except one top plate. Choose the one with the big heart if you want to see the German “du” and the one with the smaller heart if you want the English “u”.
Glue all parts expect the top plate (the one with the heart) together. Place the duplo bar inside and close the top.
I hope that the person who receives this gift will like it. Enjoy it!