Seed constellations are commonly used in self-constructing circuitry. For example, to create a faraway target object to start construction of a new copy of a construction arm at a safe distance, it is often useful to use a seed for a complex spaceship or wickstretcher -- something that can be stopped when it reaches its destination by following it with a faster spaceship or wick burning reaction.
One-glider seeds, or "1G seeds", are particularly useful in slow salvo construction because the constellation can be built up incrementally, with changes made one glider at a time. When it is complete it can be triggered by the final glider in the recipe. Triggering a seed will usually create several precisely synchronized gliders that then co-operate to construct the target object, similar to a standard glider synthesis.
Common one-glider seeds
Many common active regions have common objects that are one-glider seeds. Here is a list:
- Traffic light (can be triggered from a blinker, beehive, loaf, long boat, or toad);
- Honey farm (can be triggered from a block, beehive, loaf, boat, or toad);
- Pi-seqeunce (can be triggered from a block, blinker, beehive, boat, ship, pond, toad, beacon, or fishhook);
- R-sequence (can be triggered from a beehive, loaf, or toad);
- B-sequence (can be triggered from a boat, toad, or beacon);
- Century sequence (can be triggered from a boat, toad, or beacon);
- Wing sequence (can be triggered from a boat, ship, or beacon);
- Blockade (can be triggered from a beehive);
- Queen bee (can be triggered from a ship);
- E-sequence (can be triggered from a boat);
- Blonk-tie sequence (can be triggered from a blinker or fishhook]]
- Phi spark (can be triggered from a blinker or a boat)
The reason that so many objects are one-glider seeds for a pi-sequence is because when a glider hits a line of two cells in a still life in a certain way, the way that the glider reacts almost always produces a pentaplet grandparent of the pi-heptomino after four generations, as well as some cells behind it. For a block, beehive, boat (in one orientation), ship (in one orientation), and pond, the excess cells turn out to be sparks, so a clean pi-sequence is produced. The only common one-glider seed for a pi-sequence that does not produce the pi-this way is a blinker, which does not actually produce a pi-heptomino but instead produces a twelve-cell cluster with the same great-grandchild (hence the term pi-sequence rather than pi-heptomino).
Many spaceships and some other difficult-to-construct objects have activation stages that require many gliders coming at once from multiple directions. For uses in self-constructing circuitry, simply firing all of the gliders at once in a synchronized manner is impractical. For this reason, for the activation stage, the activation stage uses a series of turners and splitters that create all of the necessary synchronized gliders from only one initial glider that requires no synchronization.