Marble Building Blocks
These building blocks enhance the playing experience by adding motion to normal building blocks. Indentations or holes are carved into the blocks so marbles can roll down pathways created by combining the blocks. Other pieces can have simple mechanisms, like pulleys or levers, to create structures that act like Rube-Golderg machines.
Children would gain an intuition about gravity and conservation of energy by creating different pathways for the marbles. They can experiment and see how marbles roll down various configurations of blocks, like how long or how fast a marble will roll.
These blocks would be made of polished wood and sealed with a varnish so that kids would not get splinters. The blocks are very durable and would not break unless placed under great stress. Smaller pieces of the mechanisms could break off. The blocks are safe for children of most ages to play with; the main concern would be that the marbles are a choking hazard.