Bad Piggies Ground Hog Day Level 1-5 can be 3-starred with one contraption. Build a three box cart using all the parts, and placing the fan on the right side. First collect the first star box to the left. Then turn off the fan, and let gravity do the rest. Your vehicle should roll backwards down the hill, and collect the second star box before crossing the finish line.
If you have a different strategy for completing this level feel free to leave a comment below.