Trying to solve a “diabolical” grid by deduction: adding solved grid.
Slightly convoluted way of making the code much less convoluted.
One convolution less.
Yet one convolution less.
Spec less convoluted now.  Much more satisfying now, but still not ideal.
Some comments in the spec.
Spec much more satisfying now.
Created proper spec_helper.
Attempt to give the repository a clearer structure.  In progress.
Sorted out the mess of the source code.
main.rb doesn’t need to be executable any more.
Should have sorted out the mess completely now; specs moved too.
Everything really sorted now (file paths, etc.).
Basic spec for main.
Make call less awkward.
More main specs.
Added one “slow” tag to the specs.
Split one spec, and tagged one of the new as slow.
Added .rspec.
Clarifying responsibilites in main.rb