What are universal design and accessible design?

Ronald Mace coined the term universal design and defined it as follows:

“The design of products and environments to be usable by all people, to the greatest extent possible, without the need for adaptation or specialized design.”

Universal design is the concept of designing products that are usable by all people regardless of age, size, preference, ability, disability, condition, or situation. It does not focus on designing for a specific group of people but instead focuses on designing products that are useable by the widest range of people. While initially focused on architecture, the concepts of universal design have been expanded to include the design for all types of products, including video games. Accessible design is a design that specifically focuses on usability by those with impairments and disabilities and is a subset of universal design.

For a design to be effective, purposeful decisions must be made...