Simple Puzzles from a Tiling

The "target" or "object to be tiled" is a shallow bowl made from 28 sub cubes. It is composed of two layers, the bottom one a 4x4 array of cubes, the top layer the same array with the 4 central pieces removed - a sample, "bowl.stl", is included. Three puzzles are given, sets of pieces, each piece made from 7 cubes connected by their faces, which are to be assembled into the bowl. Puzzle 1 has 6 pieces, any 4 of which can be assembled to make the bowl. Puzzles 2 and 3 have 4 pieces each which assemble into the bowl. OpenSCAD code is included.