2013_12_24 - Update, today's work - See note below

Basically finished.  However,
1. The program doesn't reset appropriately if the target answer is
entered multiple times.  It works for one re-submit.
2.  The isVisible / isHidden code at lines 109 - 116 doesn't seem to be
working.  I don't know how to test it except by trial and error.
2013_12_24 - see note

Decided that I perhaps ought to keep this file.  However, I can't
commit and sync without letting it go.  So I'll recover it later.