Soma cube

Hi, I wanted to print soma cube, but it was too easy in my opinion, so I designed my own with 4 cubes per side. Together it is made from 11 pieces, and it is not as easy as it looks.
All edges are with small fillet, so there are no sharp edge.
If you have any idea for improvement, don't be shy and write a comment about it.
All my designs are modeled in my free time, so if you like them, I would appreciate small tip from you.
Enjoy printing and good luck with solving.