While I understand very little of it, it is still very enjoyable to read the details further in the thread at https://conwaylife.com/forums/viewtopic.php?&p=222136#p22221...

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It also creates ecca2, the hive needed to transition to the one-dimensional state and the ship needed at the end of the tape cleaning.

Ecca1 finishes its work by destroying its reflector on the input signal path.

Ecca2 is responsible for cleaning up the east. It is built with a destruction seed (computation supported by the gSoD program), which means that one incoming glider on the correct path will cause the pattern to disappear. The destruction seed generates two gliders. One of the goals of ecca2 is to create seeds of destruction of the reflectors on the input path - one destruction seed for the reflectors of ecca1 and one for the reflector, thus triggering the binary arm. The ship created by ecca1 near the spine converts a pair of cleaning mwss into a single glider, which triggers the destruction seed of ecca2. The exit gliders of ecca2 seed of destruction, are navigated by one time reflectors to the destruction seeds of the reflectors of ecca1 and the binary arm.

Ecca2 converts ecca1 into a ship (a disposable turner), which would play its role at the very end of the ship's period (a slow destructive salvo combined with the trivial task of pslmake). (the rest of the blinker of the binary arm stack is also destroyed by ecca2).

ECCA2 should also clean up the remains of the gun used by the binary arm (in the current version we stopped it with ecca1, but it would probably be equally or more efficient to stop it with ecca2) (slow 2 salvo is used there and half honey farm to honey farm slow salvo move collection helps a lot in such design).

The most important task of ecca2 is to stop the tape reading mechanism and clean it up. The salvo of synchronized gliders stops the GPSE90 and the corderabsorbers are assembled in time to stop the cordership pair (as a tool a program was used that automatically combines a pre-calculated splitters and reflectors (consisting of at most two small objects) to create a given pair of synchronized parallel gliders). The glider streams fired from the corderships do not stop at the same time, so the 3 escaping gliders are also stopped by the seed created by ecca2. In order for ecca2 to create a seed to stop the GPSE90, it must clean up the irregularities of the GPSE90's trajectory debris. (destructive salvo calculated into a periodic pattern...). Similarly, the far-end cleanup converts the debris of the stalled GPSE90 into a periodic pattern. Ecca2 must send corderfleets cleaning a periodic pattern (of arbitrary length). Therefore, it must create corderabsorbers on the other side (we chose corderabsorbers close, ships travelling from far). (used a program to search for corderfleets cleaning compatible periodic patterns) ... the corderships were created using modern 11 cluster seeds (except for the one closest to the arm, where 12 cluster seeds were used to fit close to the arm)).

The corderfleet was also used to destroy the remnants of a pair of corderships. The last task of ecca2 was to fire a salvo to create two mwss that would clean the blocks created during the tape reading (this would trigger a seed of ecca2 destroyal at the end).

The corderabsorber for the last cordership is modified and instead of annihilating with the cordership it emits a perpendicular glider that hits the boat from the ECCA1 conversion to bounce to the behive and converts it into a one-dimensional pattern, starting a new generation.

The ECCA2 compiler used agnosticised lane phase recipes and chose the optimal route from the options (shortening the tape as much as possible). This optimization was not done in ECCA1, binary or fuse arm.

My understanding (which could be wildly wrong, I only skimmed the thread) is that it's running in a standard 2-dimensional Game of Life grid, it just happens to start out as a 1x3.7B cell line.

It only starts out 1-dimensionally, it continues to evolve on a standard GoL grid.