Any design concept must at a very early stage in its generation take into account a great number of issues and variables which include qualities of space(s), the end-use and life-cycle of these proposed spaces, connections, relations, and aspects between spaces including how they are put together as well as the impact of proposals on the immediate and wider locality. Selection of appropriate materials and technology must be considered, tested and reviewed at an early stage in the design to ensure there are no setbacks (such as higher-than-expected costs) which may occur later. The site and its environs, as well as the culture and history of the place, will also influence the design. The design must also countenance increasing concerns with environmental sustainability. The architect may introduce (intentionally or not), to greater or lesser degrees, aspects of mathematics and architecture, new or current architectural theory, or references to architectural history.