Failure in book chapter 2 page 29: Dead cell is not a dash but a dot

[Deleted user]

Chapter 2 page 29 says "and dead cells appear as a minus character (-)", also there is a small screenshot showing lots of dashes. In fact, the source code on page 28 (and in github) is using dots, not dashes.

This is not critical, but should be fixed, as it might confuse readers.