System of play

This article is about a design program. For the theme go to System.

System of play is the concept put forth by LEGO that all LEGO products interoperate, and more specifically, that all the various elements at different age ranges, or from different themes, or from different eras, can be used together.

For example, across systems, a 2x4 System brick can be placed on top of a 1x2x2 DUPLO element because the hollow Duplo studs interlock with the tubes on the bottom of the System brick. Elements can also be placed the other way round, for example a duplo brick atop a System baseplate. This is achieved because DUPLO is exactly 2x System. There is similar interconnectivity between DUPLO and Primo.

For another example, parts from one theme within System can easily (or perhaps, in some cases, such as using Bionicle parts in town creations, not so easily) be used in other themes.

For a third example, parts from the cellulose acetate era - produced prior to 1970 can interoperate with parts of today. Similarly, 12v and 9v trains share common track gauges, and so on.