Not every simulator suits every student, so here they are grouped by age. Ages 12 to 14 start with the basics: simple mechanisms, structures, series and parallel circuits, the views of a part and first isometric drawings and dimensions. Ages 14 to 16 move on to electronics and logic gates, pneumatics and harder drawings. Ages 16 to 18 go deeper, with gear trains and pulley systems that need real calculations and the thermodynamics of a car engine. A simulator can appear in more than one age group when it has easy and advanced modes. Each one works in any browser, on a computer, a tablet or the classroom whiteboard.