That is part of the design.
Definition of DESIGN
transitive verb
1
: to create, fashion, execute, or construct according to plan : devise, contrive
2
a : to conceive and plan out in the mind <he designed the perfect crime>
b : to have as a purpose : intend <she designed to excel in her studies>
c : to devise for a specific function or end <a book designed primarily as a college textbook>
3
archaic : to indicate with a distinctive mark, sign, or name
4
a : to make a drawing, pattern, or sketch of
b : to draw the plans for <design a building>
intransitive verb
1
: to conceive or execute a plan
2
: to draw, lay out, or prepare a design