Awesomeness wrote:Is there a reaction to cut a stable gap with at least 5 diagonal squares of breathing room, and then another reaction to fill it back in, in a long snake...?
Sure -- you can find both reactions in David Bell's line-crosser from August 2006
The main cutting reaction starts at generation 10,628, and the repair happens starting generation 27,679. This was a fairly rough prototype, so there are somewhat more efficient methods available to create some of the input signals (such as the gliders parallel to and the minimum distance away from the line being cut.)
Technically it's now just about possible to do the cutting and repair, and send a glider to the far side of the line, with a mechanism that starts out all on the near side of the line. It would take an enormous shotgun, though, or a programmable constructor, and a few new reactions still need to be searched for -- in particular, a salvo to split off a new "hand" block from a constructor-arm "elbow" that has been pushed through the gap.
I've been working on this problem very slowly for the last year or two (!) but haven't made much progress since Paul Chapman's two-glider elbow-salvo searches last year, looking for a better construction arm for a new "Geminoid" spaceship or replicator. See the links in my Geminoid notes from December
for some sample salvo sets.