Puzzles often include an example of the solution. By studying the example, players can identify missing pieces of a sequence. A lot of the science in the game is correct. An electric motor must be plugged in to operate. Gears work as expected, e.g., adding another gear to a gear train reverses the direction of motion.
Balls generally bounce slowly to a stop and roll down smooth surfaces faster than rough surfaces.
This realism helps make the game fun to play as an adult. This mixture of correct and incorrect science may be confusing to kids as they try to figure out which is which. A high percentage of the puzzles involve launching rockets or otherwise blowing things up which may appeal more to boys. The tools themselves are also ones that may be more familiar to boys. In a study where we gave children an opportunity to select from any of eight games, few girls chose to play the Incredible Machine at all and one boy chose to play it exclusively.