Lego Technic is a line of Lego interconnecting plastic rods and parts that allows builders to create advanced models of working vehicles and machines compared to the simpler brick-building properties of normal Lego. Lego Technic sets contain specialized pieces such as functional motors, gears, and pneumatics that allow builders to create more complex models. The Lego Technic system expands on the normal Lego bricks with a whole range of new bricks that offer new function and building styles. The most significant change from normal Lego is that single-stud wide bricks (beams) have circular holes through their vertical face. These holes can accommodate pins, which enable two beams to be held securely together side-by-side, or hinged at an angle. Lego Technic sets tend to be a little more expensive than traditional Lego sets of a similar size due to the use of more complex pieces, engineering, and design requirements. Lego Technic sets can be enhanced further with CONTROL+, a free app that can interact with many motorized Lego Technic remote control toys to add elements like movement and sound, as well as allow children to complete challenges and share them with their friends.