In science class we're doing build projects again. This time we had to build some sorry of solar oven to cook a smore in. My group used a box with a hole cut in the top and lined with tinfoil on the inside. However that didn't really work, so we wound up opening the box and using a magnifying glass to burn the marshmallows. It started to work, but since it took so much time we only managed to cook one. Next time I'd like to find a way to somehow get the heat to focus on a bigger area to cook the marshmallows, since you have to have a pretty tiny light to actually cook it.