Maybe the biggest lesson of this accessibility-focused project is that
accessibility is not as narrow as accommodating a
specific disability by, say, testing your game with filters to simulate color blindness
(though I did do this, because it can still be helpful). Rather, accessible media is that
which accommodates as many learning styles as possible, communicating the same information
in varied ways to reach a wider audience of people who either require or benefit from multiple
channels through which to receive information.
Microsoft's Inclusive Design Principles
outline the ways that accessible media doesn't just only help
people with disabilities (e.g. ramps on sidewalks help people in wheelchairs but also people with baby strollers, luggage, etc.).
Of course, playtesting is an important component of accessibility—how are you supposed to accommodate
users if you don't know who they are?