This is a rocket stove cooktop. The idea is that the configuration allows excess oxygen to increase the burn temperature of the fire. It's not quite as efficient and clean-burning as a masonry heater, but it is much more DIY-friendly to build.
My older two boys share a room and sleep in bunk beds. Since we moved them to bunk beds it's been great as it has opened up a ton of space in their room for quiet time away from the chaos of the rest of the house. I love bunk beds.