a) Made the code that calculates the grid functional to enable the creation of testing
b) separated the code that will need to be testable in separate file (separate from html)
c) changed the modifier for double to shift + cmd
d) fixed more bugs
  - on erase, line would revert to -, as opposed to revert to -/=
  - remove neighbor fixing code that is not related to erasing
e) changed terminology from buffer to grid
f) introduced NOBRUSH instead of making it 0/null
g) introduced multi-step drawing to facilitate testing