In high school, our second year engineering classes required us to build a skittle sorter out of lego and some sensors/software.

The only requirement was a hopper for the teacher to dump the skittles into at the beginning. She would have a different amount for each group that was pre-counted and our numbers had to match hers at the end within a certain % of error.

It was a month+ long project and really fun to see each team's solution in how they moved/sorted/stored the final product. Some teams used long conveyor belts, others used short stacked belts, etc. It was all really interesting and I thoroughly enjoyed it!