ENGINO TOY SYSTEM is so versatile,  the various sets can be combined to build more and bigger models with never ending possibilities! Based on this philosophy of expandability, a new upgrade series has been created to allow users to expand their existing sets without having to buy the bigger sets at full cost. These lower cost upgrade sets, begin from the 20 models set and cover each step, up to the 80 models set. The great advantage of the upgrade sets is that they come in small boxes and take limited space and contain only the parts needed to upgrade from the existing set to the next. Even though the user can start with the basic 20 models set and expand gradually to the 80 models set, they can also expand from any other set. So,if for example the user has purchased the 40 models set they can expand it directly with 40 to 60 models upgrade. All the sets of the inventor series, from 18 models and up, include the specially designed Engino motor which is connectable to the Engino solar panel. This provides another possibility of expansion, that of powering the models with solar energy, without having to purchase a complete and more expensive solar set.