Simple and Difficult Pentomino Problems

Here are four simple puzzles made from pentominos. Puzzle 1 has 5 pentominos and forms a 5x5 square. Puzzles 2 and 3 each contain 6 pentominos and form 6x5 rectangles while Puzzle 4 has 7 pentominos and forms a 7x5 rectangle. The pieces of Puzzle 1 and Puzzle 4 when combined make a complete set of 12 pentominos, as does the combination of Puzzles 2 and 3. Printing the puzzles in different colors avoids confusion. A more difficut puzzle is to construct a "happy face" from a full 12 piece set of pentomino's. A preconstructed "key" is included as a target. See https://en.wikipedia.org/wiki/Pentomino for the letters used to indentify the individual pentominos. The full set of 12 is contained in Pentaminos.zip. More information is provided in show_answers.scad.