|View static image|
|Pattern type||Stable reflector|
|Number of cells||31|
|Discovered by||Sergey Petrov|
|Year of discovery||2013|
The colour-changing (CC) semi-Snark is a small, Spartan 90-degree colour-changing glider reflector requiring two input gliders on the same lane for each output glider. It was discovered by Sergey Petrov on 1 July 2013, using a custom-written search utility.
It functions as a very compact period doubler in some signal circuitry, for example the original 2014 spiral growth pattern. The semi-Snark can period-double a regular glider stream of period 51 or more, or an intermittent stream with two gliders every 67 ticks or more, since the block reset glider can be sent just 16 ticks before its partner.
The CC semi-Snark's discovery revolutionized self-constructing circuitry. Its small size and Spartan catalysts allowed Dave Greene in November 2013 to complete the construction of the linear propagator, which is sometimes counted as the first true replicator in Conway's Game of Life. Its use in self-constructing patterns has dropped off since then, because single-channel toolkits no longer need to retrieve multiple glider signals from a single stream. However, the CC semi-Snark is still one of the key components in stable signal converter technology, notably the doubled-signal toolkit for efficiently producing multiple synchronized gliders from a single input.