seed: rev-e, rand/block-4/k, sing pos/neg-5/6, save/load-S/L
``e'' to reset the seed. A central lower window opens up, with prompts as in #15.
``4'' to reset the seed at random, as in #15.5
``k'' to reset the seed a random central block of cells, with the remainder set to 0, as in #15.5
``5'' to reset the seed a positive singleton, a central cell set to 1 with the remainder set to 0.
``6'' to reset the seed a negative singleton, a central cell set to 0 with the remainder set to 1.
``S'' to save the seed to a ``*.eed`` file, see #15.10 and filing #28.
``L'' to load a new seed from a ``*.eed`` file, see filing #28.