Tutorials/Catalyses

A catalyst is a stable object (usually a still life) which can interact with an active region and later return to its original state. Catalysts are very useful in conduits and in many other applications. Here is an example of a stable catalyst:

x=11, y = 10, rule = LifeHistory 2.C$2.C$.2C6.2A$4.2A.A2.A$3.A.A.3A$A2.A.A$4A.3A$4.A3.A$2.A.A2.2A$2.2A ! [[ GRID THUMBNAIL THUMBSIZE 2 ]]

The green still life interacts with the white object, and recovers to its original state by generation 15. In this tutorial, you'll learn the main types of catalyses and their applications. But first, we need to cover some important definitions:

Important terms

• Stable catalyst: a catalyst which is a still life. Most catalyses are of this form. In this tutorial we will only focus on stable catalyses, as periodic catalyses are as of now quite underdeveloped.
• Periodic catalyst: a catalyst which is an oscillator. These are generally considered inferior to stable catalyses because they usually only work in a fraction of the generations as a stable catalyst, since they usually only work in one phase of the periodic catalyse.
• Recovery time: the time it takes for a catalyst to return back to its state before interacting. In the example above, the recovery time is 15.
• Replacement catalyst: When a common catalyst fails, another, less common, catalyst must be used.
• Rock: A catalyst which does not lose any of its cells, even temporarily, during the interaction process. The snake-type catalyses below are examples of rocks.

Let's explore the different types of catalysts now!

Types of common catalyses

Fishhook (eater 1)

Here are some examples of fishhook catalyses:

x=28, y = 7, rule = LifeHistory 2.A8.2A7.A.A$A.C8.AC9.C$.AC8.AC7.2AC$4.2A8.2A8.2A$4.A.A7.A.A7.A.A$6.A 9.A9.A$6.2A8.2A8.2A! [[ GRID THUMBNAIL THUMBSIZE 2 ]]

The marked white cells should always be on in a fishhook-type catalyst. Sometimes, the fishhook may engage in a more unusual manner, but these are rarer:

x=22, y = 6, rule = B3/S23 2o3b2o8b2o$3ob2o8b2o$4bo3b2o4bo3b2o$8bobo7bobo$10bo9bo$10b2o8b2o! [[ THEME 6 GRID THUMBNAIL THUMBSIZE 2 ]]

In the second example, the fishhook later catalyses a blinker. This catalysis is often useful.

Even rarer is when the tail of the eater is to be used as a rock (the red cells must not be born):

x=8, y = 7, rule = LifeHistory 6.2A$7.A$4.3A$3.DA$4.D$.3C$A3.2A! [[ GRID THUMBNAIL THUMBSIZE 2 ]]

Recognizing when to use a fishhook catalysis is really a matter of experience. For practice, try placing an eater 1 somewhere within this blue field to eat the middleweight spaceship (click on the thumbnail below to draw cells in LifeViewer using the pencil icon):

x=18, y = 9, rule = LifeHistory .5A$A4.A$5.A4.8B$A3.A5.8B$2.A7.8B$10.8B$10.8B$10.8B$10.8B! [[ GRID THUMBNAIL THUMBSIZE 2 WIDTH 800 HEIGHT 600 ]]

Block

Here are some examples of block catalyses:

x=18, y = 8, rule = LifeHistory 16.A$.A14.A$A.A5.3A6.A$A.A5.3A3.A.A$.C7.C5.C2$.2A5.2A4.2A$.2A5.2A4.2A ! [[ GRID THUMBNAIL THUMBSIZE 2 ]]

Block catalyses typically occur when there is a one cell leading edge of a pattern, shown in white above.

They are usually much easier to recognize than fishhook-type catalyses, however they may sometimes fail:

x=12, y = 6, rule = B3/S23 10b2o$ob2o5b2o$bo7bo2$b2o6b2o$b2o6b2o! [[ THEME 6 GRID THUMBNAIL THUMBSIZE 2 ]]

Moving the block over by one often fixes this problem:

x=12, y = 6, rule = B3/S23 10b2o$ob2o5b2o$bo7bo2$2o6b2o$2o6b2o! [[ THEME 6 GRID THUMBNAIL THUMBSIZE 2 ]]

As practice, try to eat this bun with a block placed in the blue region:

x=12, y = 6, rule = LifeHistory 6B$6B$6B2.3A$6B2.A2.A$6B3.2A$6B! [[ GRID THUMBNAIL THUMBSIZE 2 WIDTH 800 HEIGHT 600 ]]

Boat

Boat catalyses are rarer, but are still useful. Here are two examples:

x=23, y = 10, rule = LifeHistory 17.A$17.2A$2.A13.2A$.A.A$A2.2A$.2CB16.2DB2$2.A18.A$.A.A16.A.A$.2A17.2A! [[ GRID THUMBNAIL THUMBSIZE 2 ]]

They typically occur when there is a two cell leading edge, which is marked. Boat catalyses fail very often, so see the "Replacement catalysts" section below for potential replacement catalysts. As a general rule, boats are most likely to succeed when a cell adjacent to the leading edge (shown in blue) will turn on in the following generation.

Boats can also catalyze objects with a line of three cells, but it's important here that the red cell does not turn on:

x=8, y = 6, rule = LifeHistory 3.A3.A$6.A$2.D3C$.A$A.A$2A! [[ GRID THUMBNAIL THUMBSIZE 2 ]]

Snake

Snake catalyses are examples of rocks, or catalysts which do not change even temporarily when interacting with an object. They must function this way due to the fact that the two cells in the center would die from overpopulation due to already having three live neighbors.

Three example snake catalysts are shown below. The white cells should always be on to trigger the important next generation, where the snake functions as a rock:

x=24, y = 9, rule = LifeHistory 15.A6.A$4.A8.2A8.A$2A.2A6.2A7.A.2A$.C9.C9.C2$2.2A8.2A8.2A$3.A9.A9.A$ 2.A9.A9.A$2.2A8.2A8.2A! [[ GRID THUMBNAIL THUMBSIZE 2 ]]

Both the eater head and eater tail can function as a snake catalyst:

x=25, y = 7, rule = LifeHistory A.3A5.A.3A5.A.3A$.C9.C9.C2$2.2A8.2A8.2A$3.A9.A9.A$2.A10.A.A4.3A$2.2A 10.2A4.A! [[ GRID THUMBNAIL THUMBSIZE 2 ]]

It's important that the following red cell does not get born. Try replacing with a hook-with-tail if the red cell gets born.

x=15, y = 7, rule = LifeHistory 2A.2A4.2A.2A$2.C.D6.C.D2$3.2A5.A.A$4.A5.2A.A$3.A9.A$3.2A8.2A! [[ GRID THUMBNAIL THUMBSIZE 2 ]]

Conduit 1 is an example of a conduit using a snake catalyst. Try to catalyze the reaction below with a snake in the blue field (as a hint, the cell which should trigger the rock interaction is marked):

x=15, y = 7, rule = LifeHistory 7B$7B4.2A.A$7B5.3A$7B6.A$7BD$7B4.2A$7B4.2A! [[ GRID THUMBNAIL THUMBSIZE 2 WIDTH 800 HEIGHT 600 ]]

Tub

Tub catalyses can be tricky to find, but they are most likely to work when the frontend of the active region is two or three cells long, like one of the examples below:

x=39, y = 73, rule = LifeHistory 25.A12.A$4.A5.A10.A3.A$3A5.A.A15.A7.A.2A$3A5.3A7.3A6.2A6.2A2$2.A7.A7. A7.A7.A$.A.A5.A.A5.A.A5.A.A5.A.A$2.A7.A7.A7.A7.A4$17.A2$17.A2$14.A2.A 2.A2$15.A.A.A2$17.A3$.A7.A15.2A10.A$A.2A4.A.2A7.2A5.2A8.2A$A.A5.A.A8. A7.A7.3A$2.C7.C7.C8.C7.C$2.A7.A7.A7.A7.A$.A.A5.A.A5.A.A5.A.A5.A.A$2.A 7.A7.A7.A7.A4$17.A2$17.A2$14.A2.A2.A2$15.A.A.A2$17.A3$.2A6.2A14.3A8. 2A$A.2A4.A.2A7.2A4.A.A7.A2.A$2.A7.A7.3A6.2A6.A.A$2.2C6.2C6.2C6.2C6.2C $.2AC5.2AC5.2AC6.AC6.AC$.A.A5.A.A5.A.A5.A.A5.A.A$2.A7.A7.A7.A7.A4$17. A2$17.A2$14.A2.A2.A2$15.A.A.A2$17.A4$26.A$.3A5.3A13.A.A8.2A$3.A7.A6.A .A4.A9.A2.A$28.A6.A2$.A2.A4.A2.A4.A2.A4.A2.A4.A2.A$.A.A5.A.A5.A.A5.A. A5.A.A$2.A7.A7.A7.A7.A! [[ GRID THUMBNAIL THUMBSIZE 2 WIDTH 500 HEIGHT 700 ]]

The reactions start differently but end up the same way through the same general mechanism:

• On generation 1, one cell (marked in white) is born next to the tub;
• On generation 2, two more cells are born next to the tub. This causes the three white cells to die;
• By generation 3, the cells in the center have died and what remains is a 5-cell parent of the tub. In all tub catalyses, the tub should turn into this 5-cell parent.

Replacement catalyses

So, you've tried to catalyze a reaction, but the common catalyst fails! Luckily for you, this is not a complete disaster, since many replacement catalysts exist exactly to assist you when your fishhook or block doesn't just work out.

Fishhook replacements

The most common way for a fishhook to fail is something like this:

x=8, y = 8, rule = B3/S23 o$o2bo$b3o2$4b2o$4bobo$6bo$6b2o! [[ THEME 6 GRID THUMBNAIL THUMBSIZE 2 ]]

Luckily, this is also the easiest to fix. Simply flip the eater 1 around and it works!

x=32, y = 9, rule = B3/S23 o15bo$o2bo20bo$b3o14bo5bo2bo$25b3o$4b2o4bobobobobobo$4bobo21b2o$6bo11b o9bo$6b2o21b3o$16bo14bo! [[ THEME 6 GRID THUMBNAIL THUMBSIZE 2 ]]

This was a bit cheating, however. Sometimes, we need a genuinely new catalyst. Here are two almost-catalyses where the fishhook almost recovers, but an extra spark destroys it or an extra cell gets attached to its recovering phase:

x=20, y = 8, rule = B3/S23 12bo$o10bobo$b2o10b2o$2o12bo$4b2o7bo2b2o$4bobo9bobo$6bo11bo$6b2o10b2o! [[ THEME 6 GRID THUMBNAIL THUMBSIZE 2 ]]

The most common replacement catalyst for a fishhook is the handy eater 2. An eater 2 recovers differently from an eater 1, making it more versatile. It can handle both of our problems:

x=23, y = 11, rule = B3/S23 12bo$o10bobo$b2o10b2o$2o12bo$4b2obo5bo2b2obo$4b2ob3o6b2ob3o$10bo11bo$ 4b2ob3o6b2ob3o$5bobo9bobo$5bobo9bobo$6bo11bo! [[ THEME 6 GRID THUMBNAIL THUMBSIZE 2 ]]

There are many, many more cases in which neither an eater 1 nor an eater 2 works. This guide, courtesy of Entity Valkyrie, addresses many of these:

x=975, y = 63, rule = EV2QuadColor 99.3F.3F.3F61.3F.3F.3F61.3F.3F.3F61.3F.3F.3F61.3F.3F.3F61.3F.3F.3F61.3F.3F.3F61.3F.3F.3F61.3F.3F.3F61.3F.3F.3F61.3F.3F.3F61.3F.3F.3F61.3F.3F.3F$27.3F.3F.3F61.F3.F3.F.F61.F3.F3.F.F61.F3.F3.F.F61.F3.F3.F.F61.F3.F3.F.F61.F3.F3.F.F61.F3.F3.F.F61.F3.F3.F.F61.F3.F3.F.F61.F3.F3.F.F61.F3.F3.F.F61.F3.F3.F.F61.F3.F3.F.F$27.F3.F3.F.F61.F3.2F2.F.F61.F3.2F2.F.F61.F3.2F2.F.F61.F3.2F2.F.F61.F3.2F2.F.F61.F3.2F2.F.F61.F3.2F2.F.F61.F3.2F2.F.F61.F3.2F2.F.F61.F3.2F2.F.F61.F3.2F2.F.F61.F3.2F2.F.F61.F3.2F2.F.F$27.F3.2F2.F.F61.F.F.F3.F.F61.F.F.F3.F.F61.F.F.F3.F.F61.F.F.F3.F.F61.F.F.F3.F.F61.F.F.F3.F.F61.F.F.F3.F.F61.F.F.F3.F.F61.F.F.F3.F.F61.F.F.F3.F.F61.F.F.F3.F.F61.F.F.F3.F.F61.F.F.F3.F.F$27.F.F.F3.F.F61.3F.3F.F.F61.3F.3F.F.F61.3F.3F.F.F61.3F.3F.F.F61.3F.3F.F.F61.3F.3F.F.F61.3F.3F.F.F61.3F.3F.F.F61.3F.3F.F.F61.3F.3F.F.F61.3F.3F.F.F61.3F.3F.F.F61.3F.3F.F.F$27.3F.3F.F.F$103.3F69.3F69.3F69.3F69.3F69.3F69.F.F69.3F69.3F69.3F69.F.F69.F.F69.F.F$31.3F71.F71.F71.F69.F73.F71.F69.F.F71.F69.F73.F69.F.F69.F.F69.F.F$33.F69.3F69.3F71.F69.3F69.3F69.3F69.3F69.3F69.3F69.3F69.3F69.3F69.3F$31.3F69.F71.F73.F71.F71.F71.F71.F69.F73.F69.F73.F71.F71.F$31.F71.3F69.3F71.F69.3F69.3F69.3F71.F69.3F69.3F69.3F71.F71.F71.F$31.3F2$864.2D$D504.D.D26.A112.D73.D142.3D$.3D70.D70.D68.D5.D67.D146.D71.D25.A2.A41.D69.D70.D.D71.2D70.D.2D$3.D16.H54.D16.H51.D.D17.H48.2D2.4D15.H51.3D17.H71.H54.D16.H10.A40.D2.D16.H9.3A41.D17.H51.D19.H51.D.D17.H54.D16.H51.2D.2D15.H49.D21.H$3.D16.2H10.A42.D16.2H50.D.2D16.2H47.D2.D2.D16.2H50.4D16.2H53.D16.2H51.D.D16.2H8.2A42.2D16.2H9.A43.D16.2H51.D.D16.2H9.A42.2D16.2H53.D16.2H48.D4.D16.2H9.A38.D3.2D16.2H8.A$3.D12.7H50.3D12.7H6.A45.D12.7H50.3D12.7H48.2D2.D12.7H9.A37.2D3.D12.7H51.2D12.7H51.2D12.7H51.2D12.7H50.3D12.7H7.A42.D.D12.7H7.A42.D.D12.7H49.D2.D12.7H48.D3.D12.7H8.A$5.2E9.8H7.AFE43.2E9.8H5.A2.FE40.D2.2E9.8H6.A.FE43.2E9.8H8.2E39.2D2.2E9.8H8.2E38.3D2.2E9.8H8.FE43.2E9.8H8.2E43.2E9.8H8.2E39.2D2.2E9.8H8.FE43.2E9.8H6.A.FE43.2E9.8H6.A.FE43.2E9.8H8.FE38.3D2.2E9.8H8.2E38.3D2.2E9.8H8.2E$5.E.E8.7H8.AE.E42.E.E8.7H8.AE.E42.E.E8.7H8.AE.E42.E.E8.7H9.E.E42.E.E8.7H9.E.E42.E.E8.7H9.E.E42.E.E8.7H9.E.E42.E.E8.7H9.E.E42.E.E8.7H9.E.E42.E.E8.7H8.AE.E42.E.E8.7H8.AE.E42.E.E8.7H7.A.E.E42.E.E8.7H7.A.E.E42.E.E8.7H7.A.E.E$7.E12.2H12.E44.E12.2H12.E44.E12.2H12.E44.E12.2H10.A.E44.E12.2H12.E44.E12.2H12.E44.E12.2H12.E44.E12.2H12.E38.D5.E12.2H12.E44.E12.2H12.E44.E12.2H12.E44.E12.2H9.A2.E34.2D8.E12.2H12.E44.E12.2H12.E$7.2E11.H13.2E43.2E11.H13.2E43.2E11.H13.2E43.2E11.H13.2E43.2E11.H13.2E43.2E11.H13.2E43.2E11.H13.2E43.2E11.H13.2E43.2E11.H13.2E43.2E11.H13.2E43.2E11.H13.2E43.2E11.H13.2E34.D8.2E11.H13.2E43.2E11.H13.2E9$367.2E25.2E468.2D$D366.E.E24.E.E108.D.D139.D73.D142.3D$.3D70.D70.D68.D5.D67.D80.E26.E38.D71.D70.D69.D70.D.D71.2D4.2E25.2E37.D.2D$3.D16.J54.D16.J51.D.D17.J48.2D2.4D15.J51.3D17.J59.2E.2E7.J14.2E.2E35.D16.H10.A40.D2.D16.J53.D17.H51.D19.H51.D.D17.H54.D4.E11.J14.E36.2D.2D65.D21.H$3.D16.2J10.A42.D16.2J50.D.2D16.2J47.D2.D2.D16.2J50.4D16.2J53.D5.E.E8.2J14.E.E34.D.D16.2H8.2A42.2D3.E12.2J12.E40.D16.2H51.D.D16.2H52.2D16.2H53.D4.E.2E8.2J13.E.2E31.D4.D27.A38.D3.2D16.2H8.A$3.D12.7J50.3D3.2E7.7J6.A4.2E39.D12.7J50.3D12.7J48.2D2.D12.7J9.A37.2D3.D2.3E2.E4.7J10.F2E2.E35.2D12.7H51.2D2.E.E7.7J10.E.E38.2D3.2E7.7H9.A.2E37.3D3.2E7.7H11.2E37.D.D12.7H7.A42.D.D2.3E2.E4.7J10.EFE2.E33.D2.D4.2E25.2E34.D3.D12.7H8.A$5.2E9.8J7.AFE43.E2.E7.8J5.A2.F2.E38.D2.2E.E7.8J6.A.FE.E41.2E9.8J8.FE39.2D2.2E9.8J8.FE38.3D2.E3.2E5.8J8.F3.2E39.2E.E7.8H8.EF.E41.E2.E7.8J8.F.AE37.2D2.E2.E7.8H8.F2.E41.E2.E7.8H7.AF2.E41.2E.E7.8H6.A.FE.E41.E3.2E5.8J8.F3.2E34.3D2.2E2.E22.2E2.E35.3D2.2E.E7.8H8.2F.E$5.E2.E7.7J8.AF2.E41.3E8.7J8.4E42.2E.3E5.7J8.AFE.3E39.E.E.2E5.7J9.E.E.2E39.E.E.2E5.7J9.F.E.2E39.4E7.7J9.4E41.2E.3E5.7H9.EF.3E39.2E.E.2E4.7J9.2E.E.2E38.3E8.7H9.3E42.3E8.7H7.2AF2E42.2E.3E5.7H8.AFE.3E39.4E7.7J9.F3E41.E.2E23.F.2E41.2E.3E5.7H7.A.2EA3E$6.2E.E10.2J11.2E.E55.2J61.E8.2J16.E40.E.E10.2J9.2A.E.E42.E.E10.2J9.2A.E.E43.E11.2J9.A3.E47.E8.2H11.A4.E39.E.E2.E8.2J11.E.E2.E34.D18.2H70.2H9.A51.E8.2H16.E41.E11.2J13.E33.2D8.E22.A.A.E48.E8.2H9.A.A4.E$9.E10.J15.E40.2E.E.2E8.J11.2E.E.2E38.2E.3E9.J11.2E.3E40.2E2.E9.J11.AFE2.E40.2E2.E9.J12.2E2.E39.2E.E.E9.J11.2E.E.E39.2E.3E9.H11.2E.3E38.E.E.2E10.J10.E.E.2E40.2E.E.2E8.H11.2E.E.2E38.2E.E.2E8.H11.2E.E.2E38.2E.3E9.H11.2E.3E39.2E.E.E9.J11.2E.E.E32.D6.E.E24.F.E42.2E.3E9.H11.2E.3E$9.2E25.2E40.E.2E.E21.E.2E.E39.E.E24.E.E44.2E22.A2.2E43.2E25.2E41.E2.2E22.E2.2E40.E.E24.E.E40.2E25.2E45.E.2E.E21.E.2E.E39.E.2E.E21.E.2E.E39.E.E24.E.E42.E2.2E22.E2.2E39.2E25.2E44.E.E24.E.E$78.E26.E44.E.E24.E.E42.2E25.2E43.2E25.2E41.E.E24.E.E44.E.E24.E.E114.E26.E44.E26.E44.E.E24.E.E40.E.E24.E.E116.E.E24.E.E$77.2E25.2E45.E26.E44.E26.E44.E26.E41.2E25.2E46.E26.E114.2E25.2E43.2E25.2E45.E26.E41.2E25.2E118.E26.E$223.E.E24.E.E42.E.E24.E.E$224.2E25.2E43.2E25.2E5$D646.D73.D$.3D431.D142.D4.2E25.2E36.D70.D.D$3.D16.J359.J54.D5.E10.J15.E109.D5.E11.J14.E36.D19.J51.D.D17.J193.D21.J$3.D16.2J341.D16.2J51.D.D3.3E10.2J12.3E110.D4.E.2E8.2J13.E.2E34.D.D16.2J52.2D16.2J192.D3.2D16.2J8.A$3.D2.2E8.7J10.2E323.2D3.D12.7J51.2D2.E9.7J10.E112.2D2.3E2.E4.7J10.3E2.E34.3D3.2E7.7J11.2E37.D.D2.2E8.7J7.A2.2E180.D3.D12.7J8.A$5.E.E8.8J7.AF.E325.3D2.2E9.8J8.FE43.E.E8.8J8.E.E110.2D2.E3.2E5.8J8.F3.2E39.E2.E7.8J8.E2.E41.E.E8.8J6.A.F.E181.3D2.2E.E7.8J8.2F.E$5.E10.7J9.E332.E.E8.7J9.E.E42.E.E8.7J9.E.E114.4E7.7J9.4E41.3E8.7J9.3E42.2E9.7J8.A2E187.2E.3E5.7J9.2EA3E$3.E.E14.2J8.E.E334.E12.2J10.A.E39.E3.E13.2J7.E3.E111.D6.E11.2J13.E38.E17.2J7.E51.2E9.2J14.2E189.E8.2J11.A4.E$.3E.E.E12.J7.3E.E.E331.2E.2E.E7.J12.2E.2E.E34.4E14.J8.4E116.2E.E.E9.J11.2E.E.E36.4E14.J8.4E41.2E5.E.E8.J8.2E5.E.E180.4E.3E9.J9.4E.3E$E5.2E19.E5.2E327.2E2.E2.E.2E16.2E2.E2.E.2E182.E2.2E22.E2.2E39.E26.E42.E7.E18.E7.E180.E3.2E21.E3.2E$2E25.2E332.E.E3.2E19.E.E3.2E38.2E25.2E117.E.E24.E.E42.E26.E40.3E8.2E14.3E8.2E180.2E25.2E$361.E26.E45.2E25.2E117.2E25.2E43.2E25.2E39.E26.E194.2E.E23.2E.E$360.2E25.2E553.E.2E23.E.2E! [[ THUMBNAIL THUMBSIZE 2 WIDTH 1200 HEIGHT 400 ]]

Here is an addendum by MathAndCode:

x=327, y = 59, rule = EV2QuadColor 100.3F.3F.3F61.3F.3F.3F61.3F.3F.3F61.3F.3F.3F$28.3F.3F.3F61.F3.F3.F.F61.F3.F3.F.F61.F3.F3.F.F61.F3.F3.F.F$28.F3.F3.F.F61.F3.2F2.F.F61.F3.2F2.F.F61.F3.2F2.F.F61.F3.2F2.F.F$28.F3.2F2.F.F61.F.F.F3.F.F61.F.F.F3.F.F61.F.F.F3.F.F61.F.F.F3.F.F$28.F.F.F3.F.F61.3F.3F.F.F61.3F.3F.F.F61.3F.3F.F.F61.3F.3F.F.F$28.3F.3F.F.F$104.F.F69.3F69.F.F69.3F$32.3F69.F.F71.F69.F.F69.F$32.F71.3F69.3F69.3F69.3F$32.3F71.F71.F71.F71.F$34.F71.F69.3F71.F69.3F$32.3F2$73.D$293.D.D$3.D68.D.D144.D66.D$4.D16.H53.2D16.H54.D16.H54.D16.H49.3D3.D15.H$4.D16.2H50.D.2D16.2H53.D16.2H8.D44.D16.2H53.D16.2H$4.D12.7H9.A41.2D12.7H51.2D12.7H7.D42.D.D12.7H51.2D12.7H10.A$D5.2E9.8H8.FE43.2E9.8H6.A.2E43.2E9.8H8.2E43.2E9.8H5.A2.FE43.2E9.8H8.2F$.3D2.E.E8.7H9.E.E42.E.E8.7H8.AE.E42.E.E8.7H9.E.E42.E.E8.7H7.A.E.E42.E.E8.7H8.AE.E$8.E12.2H12.E44.E12.2H12.E44.E12.2H12.E44.E12.2H9.A2.E44.E12.2H12.E$8.2E11.H13.2E43.2E11.H13.2E43.2E11.H13.2E43.2E11.H13.2E43.2E11.H13.2E9$73.D$293.D.D$3.D68.D.D144.D66.D$4.D16.J53.2D16.J54.D16.J54.D16.J49.3D3.D15.J$4.D16.2J50.D.2D16.2J53.D16.2J8.A44.D16.2J53.D16.2J$4.D12.7J51.2D3.2E7.7J11.2E38.2D12.7J7.A42.D.D12.7J51.2D3.2E7.7J11.2E$D5.2E9.8J8.2E43.E2.E7.8J6.A.E2.E41.2E.E7.8J8.EF.E41.2E9.8J8.FE43.E2.E7.8J8.F2.E$.3D2.E.E8.7J9.E.E42.3E8.7J9.3E42.2E.3E5.7J9.EF.3E39.E.E8.7J8.AE.E42.3E8.7J8.A3E$7.2E12.2J11.2E57.2J9.A51.E8.2J11.A4.E35.E4.E12.2J7.E4.E39.E17.2J7.E$21.J56.2E.E.2E8.J11.2E.E.2E38.2E.3E9.J11.2E.3E36.5E13.J8.5E40.4E14.J8.4E$79.E.2E.E21.E.2E.E39.E.E24.E.E113.E26.E$79.E26.E44.E.E24.E.E40.E26.E44.E26.E$78.2E25.2E45.E26.E40.E.E24.E.E43.2E25.2E$221.E26.E5$73.D2$72.D.D$75.2D16.J$73.D.2D3.2E11.2J12.2E$75.2D4.E7.7J9.A2.E$78.3E8.8J6.A.3F$78.E10.7J8.AE.A$93.2J$93.J! [[ THUMBNAIL THUMBSIZE 2 WIDTH 1200 HEIGHT 400 ]]

Block replacements

Sometimes, a block that fails only needs to be supported with another catalyst, not replaced entirely. Take this, for example:

x=9, y = 9, rule = LifeHistory 2.2A$2.2A2$5.3D2$7.2A$.3A3.2A$.A.A$.A.A! [[ GRID THUMBNAIL THUMBSIZE 2 ]]

The catalyst almost works, but then an extra blinker, shown in red, destroys it. If only we could get rid of that blinker...

Oh, right! We can use what we just learned in this tutorial! Adding an extra fishhook suppresses the blinker and allows the catalyst to work:

x=12, y = 10, rule = B3/S23 11bo$2b2o5b3o$2b2o4bo$8b2o3$7b2o$b3o3b2o$bobo$bobo! [[ GRID THUMBNAIL THEME 6 THUMBSIZE 2 ]]

This trick works in a variety of circumstances where a block fails because unwanted cells are born to one side. Also, the fishhook can occasionally be replaced by a block.

x=71, y = 28, rule = B3/S23 15bo19bo13b2o$15bo18bo14b3o$o16bobo13bo14bob2o$3o14bobo13bobo12b3o$bo 16bo15bo14bo2$b2o14b2o14b2o14b2o$b2o14b2o14b2o14b2o10$15bo19bo13b2o14b 2o$15bo18bo14b3o13b3o$o16bobo13bo14bob2o12bob2o$3o14bobo13bobo12b3o13b 3o$bo16bo15bo14bo15bo$69b2o$b2o14b2o14b2o14b2o14b2o2b2o$b2o2b2o10b2o2b 2o10b2o2b2o10b2o2b2o10b2o$5bobo13bobo13bobo13bobo$7bo15bo15bo15bo$7b2o 14b2o14b2o14b2o! [[ GRID THUMBNAIL THEME 6 THUMBSIZE 2 ]]

Another example where a block catalyst can be fixed by supporting the block with another catalyst comes from the following example, where the block is turned into a first cousin of the century then crashes into a boat.

x=5, y = 8, rule = B3/S23 b2o$b2o3$3o$obo$3bo$4bo! [[ GRID THUMBNAIL THEME 6 THUMBSIZE 2 ]]

In this case, the block can be supported by another block. In fact, two positions work.

x=24, y = 8, rule = B3/S23 5b2o13b2o$2o3b2o13b2o$2o13b2o$15b2o$4b3o12b3o$4bobo12bobo$7bo14bo$8bo14bo! [[ GRID THUMBNAIL THEME 6 THUMBSIZE 2 ]]

This trick only works if there is something for the century cousin to crash into (and even then, not always), but luckily, there is an actual replacement catalyst for when the block is turned into a century cousin with nothing to hit.

x=19, y = 10, rule = B3/S23 o11bo$b3o9b3o$2bo11bo2$2b2o10b2o2bo$2b2o9bob4o$11b3o$10bo3b3o$11b3o2bo$13bo!5b2o13b2o$2o3b2o13b2o$2o13b2o$15b2o$4b3o12b3o$4bobo12bobo$7bo14bo$8bo14bo! [[ GRID THUMBNAIL THEME 6 THUMBSIZE 2 ]]

There is another replacement catalyst for when the block is turned into an L-tetromino (a common beehive predecessor).

x=22, y = 14, rule = B3/S23 3bo15bo$3bo15bo$3bo15bo$3bo15bo$3o13b3o$bo15bo2$b2o14b2o$b2o12bo2bo$15b 2obobo$18b2obo$15b3o3bo$15bo2b3o$18bo! [[ GRID THUMBNAIL THEME 6 THUMBSIZE 2 ]]

It should be noted that when a block fails in one of the most recent two ways, it can often be replaced with a hook with tail (although the hook with tail is not a replacement catalyst for the block in the strictest sense).

x=17, y = 25, rule = B3/S23 15bo$15bo$15bo$o14bo$b3o8b3o$2bo10bo2$2b2o9b2o$2b2o9b2o6$15bo$15bo$15b o$o14bo$b3o8b3o$2bo10bo2$bobo8bobo$b2obo7b2obo$4bo10bo$4b2o9b2o! [[ GRID THUMBNAIL THEME 6 THUMBSIZE 2 ]]

If a block is turned into a P-pentomino in a certain way, it can be replaced with a boat—or a fishhook bridge fishhook.

x=32, y = 9, rule = B3/S23 bo10bo10bo$4obo5b4obo5b4obo$4bo10bo10bo2$4b2o9b2o9b2o$4b2o9bobo8bobo$ 16bo7bobob3o$24b2o5bo$30b2o! [[ GRID THUMBNAIL THEME 6 THUMBSIZE 2 ]]

There is another replacement catalyst for another way in which the block is sometimes turned into a P-pentomino.

x=20, y = 13, rule = B3/S23 obo11bobo$b2o12b2o$3bobo11bobo$3bobo11bobo$4bo13bo2$3b2o12b2o$3b2o12b 2o$14bo$14b5o$18bo$16bo$16b2o! [[ GRID THUMBNAIL THEME 6 THUMBSIZE 2 ]]

In addition, there is a third way in which a block is sometimes turned into a P-pentomino. In this case, it can be replaced with a claw with tail supported by a fishhook.

x=21, y = 10, rule = B3/S23 3bo13bo$3bo13bo$obo11bobo$bo13bo2$b2o12b2o$b2o8b2o2bo2bo$10bobo3b2obo $10bo8bo$9b2o8b2o! [[ GRID THUMBNAIL THEME 6 THUMBSIZE 2 ]]

This also works if it's turned into an L-tetromino.

x=21, y = 10, rule = B3/S23 2bo13bo$3bo13bo$obo11bobo$bo13bo2$b2o12b2o$b2o8b2o2bo2bo$10bobo3b2obo $10bo8bo$9b2o8b2o! [[ GRID THUMBNAIL THEME 6 THUMBSIZE 2 ]]

Boat replacements

Here is an example of a boat in need:

x=3, y = 8, rule = LifeHistory .A$2.A$3A2$D$.A$A.A$.2A! [[ GRID THUMBNAIL THUMBSIZE 2 ]]

In this example, the white cell at generation 4 gets turned on when it shouldn't. We have a fix for this, as usual. Replace the boat with a tub with tail and block (this catalyst is called an eater 5 or tub-with-tail eater:

x=9, y = 10, rule = B3/S23 5bo$6bo$4b3o2$2o$2o3bo$4bobo$5bobo$7bo$7b2o! [[ GRID THUMBNAIL THEME 6 THUMBSIZE 2 ]]

Boats can also fail much more spectacularly:

x=8, y = 4, rule = B3/S23 6bo$3o2bobo$obo3b2o$obo! [[ GRID THUMBNAIL THEME 6 THUMBSIZE 2 ]]

In this case, the boat can be replaced by this (often called the "gourmet catalyst" due to its use in gourmet):

x=10, y = 10, rule = B3/S23 8b2o$7bobo$7bo$6b2o2$6b2o$3o2bobo$obo3bo$obo4b3o$9bo! [[ GRID THUMBNAIL THEME 6 THUMBSIZE 2 ]]

Note that this doesn't always work, since it requires a spark to recover properly.

Snake replacements

The only way to replace snake catalyses is by replacing them with a similar catalyst which does the same thing but might have better clearance. For example, if a snake is required to be in close proximity to a fishhook, the fishhook's interaction might destroy the snake (and subsequently the fishhook). In this case, replacing the snake with a higher-clearance second fishhook can prevent the interaction:

x=36, y = 9, rule = B3/S23 7bo26bo$2o4bo20b2o4bo$bo4b3o8bo10bo4b3o$o18bo5b3o$2o23bo$3b2o6bobobob obobo8b2o$4bo26bo$b3o15bo8b3o$bo15bo10bo! [[ GRID THEME 6 THUMBNAIL THUMBSIZE 2 ]]

Tub replacements

Sometimes, a single dot at the end of the tub parent is replaced with a line of three cells, causing the tub to turn into a block instead of recovering:

x=24, y = 12, rule = LifeHistory 22.2A$21.2A$20.2A$A5.A2$.2A.2A$3.A$6.D15.D$6.D15.D$4.A15.A$3.A.A13.A. A$4.A15.A! [[ GRID THUMBNAIL THUMBSIZE 2 ]]

When this occurs, the tub should be replaced with this catalyst:

x=30, y = 18, rule = B3/S23 23b2o$22b2o$21b2o$bo5bo2$2b2ob2o$4bo3$5bo15bo$4bobo13bobo$3bobo13bobo$ b3o2b3o3b2o3b3o2b3o3b2o$o3b2o3bo2b2o2bo3b2o3bo2b2o$b3o2b2obo7b3o2b2obo $3bobo2bo10bobo2bo$4bobo13bobo$5bo15bo! [[ GRID THUMBNAIL THEME 6 THUMBSIZE 2 ]]

If this line of three cells is connected to something at the other end, a boat supported by a fishhook works:

x=21, y = 20, rule = LifeHistory 3.A$3.A10.A$3AD9.2D$3A.D8.2AC$4.D10.D$2.A10.A$.A.A8.A.A$2.A10.A3$3.A$ 3.A10.A$3AD9.2D$3A.D8.2AC$4.D10.D$2.A10.A$.A.A2.2A4.A.A2.2A$.2A3.A.A3. 2A3.A.A$8.A10.A$8.2A9.2A! [[ GRID THUMBNAIL THUMBSIZE 2 ]]

If the line is instead four or more cells long, a 15-cell catalyst works:

x=18, y = 23, rule = LifeHistory 16.A$6.A9.AD$2.A3.A9.AD$3.A.A.D9.D$4.A2.D7.2AC$7.D9.D$5.A9.A$4.A.A7.A .A$5.A9.A3$16.A$6.A9.AD$2.A3.A9.AD$3.A.A.D9.D$4.A2.D7.2AC$7.D9.D$5.A9. A$4.A.A7.A.A$3.A.A7.A.A$.3A.A.A3.3A.A.A$A5.2A2.A5.2A$2A8.2A! [[ GRID THUMBNAIL THUMBSIZE 2 ]]

Bonus catalyses

Here are some extra catalyses which might come in useful. This section is optional as the catalysts used are fairly rare.

Eater 3

You might notice that when you hit a loaf with a glider in a certain way, the loaf flips around:

x=15, y = 14, rule = B3/S23 2bo$obo$b2o$5b2o$4bo2bo$4bobo$5bo5$12b3o$12bo$13bo! [[ GRID THEME 6 THUMBNAIL THUMBSIZE 2 ]]

This is quite inconvenient for us because we can't use the loaf again (unless we flip it back around with another glider as shown in the viewer, which is unlikely), but a stable catalyst does exist to turn the loaf back around. Here is the eater 3:

x=16, y = 15, rule = b3s23 2bo$obo$b2o$5b2o$4bo2bo2b2o$4bobo4bo2bo$5bo5bobobo$8b2obo2bo$8bo2bo$5b o4bo$5b5o2$7bo$6bobo$7bo! [[ GRID THEME 6 THUMBNAIL THUMBSIZE 2 ]]

There is also a drifty variant of the eater 3 that catalyzes in the same way, but recovers differently:

x=11, y = 10, rule = b3s23 o$b2o$2o7b2o$4b2obo2bo$3bobob3o$3bobo$b3ob5o$o3bo4bo$2o2bobo$5b2o! [[ GRID THEME 6 THUMBNAIL THUMBSIZE 2 ]]

The eater 3 has some other applications besides eating gliders, for example the rectifier.

Ship

The ship has a transparent catalysis not similar to other catalysts where it deletes half of a traffic light:

x=7, y = 6, rule = B3/S23 b2o$obo$2o2$5bo$4b3o! [[ GRID THEME 6 THUMBNAIL THUMBSIZE 2 ]]

This may seem pretty niche, but it is actually a fairly common application.

Hook with tail

The hook with tail can serve as a rock:

x=30, y = 13, rule = B3/S23 19b2o2$21bo$19bo2bo4b2o$19bo2bo4bobo$20b3o5bo$b2ob2o5b3o$3bo8bo2$2bob o6bobo6bobo$bob2o5bob2o5bob2o$bo8bo8bo$2o7b2o7b2o! [[ GRID THEME 6 THUMBNAIL THUMBSIZE 2 ]]

One of its most common uses is to compactify the eater 5, called the 7x9 eater, which is used in a variety of conduits including the syringe:

x=14, y = 7, rule = B3/S23 3b2ob2o3b2o$2bobobobo2bobo$2bobo2bo3bo$b2obo$o3b2o$bobo2bobo$2ob2o2b2o ! [[ GRID THEME 6 THUMBNAIL THUMBSIZE 2 ]]

Ship (again)

Observe the following reaction:

x=8, y = 9, rule = B3/S23 2bo$2o$b2o$3b3o3$5b2o$5bobo$6b2o! [[ THEME 6 GRID THUMBNAIL THUMBSIZE 2 ]]

The ship rarely recovers by its own, but it's worth trying because it has replacement catalysts that recover much more often.

Often, the ship is turned into a loaf. Adding a fishhook turns it back into a ship:

x=46, y = 30, rule = LifeHistory 14.A$16.2A$16.4A21.A$.A11.A4.A7.A15.A$2.A.A9.3A10.2A11.A.A$3.A12.A12. A12.A2$4.2A11.2A11.2A11.2A$4.A.A10.A.A10.A.A10.A.A$4.D2A10.D2A10.D2A10. D2A6$14.A$16.2A$16.4A21.A$.A11.A4.A7.A15.A$2.A.A9.3A10.2A11.A.A$3.A12. A12.A12.A2$4.2A11.2A11.2A11.2A$4.A.A10.A.A10.A.A10.A.A$5.2A11.2A11.2A 11.2A2$2.2A11.2A11.2A11.2A$3.A12.A12.A12.A$3A10.3A10.3A10.3A$A12.A12. A12.A! [[ GRID THUMBNAIL THUMBSIZE 2 ]]

If the loaf parent has an extra cell in a certain position, there's another replacement catalyst that works (which was discovered fairly recently to use in the R49 conduit, so it is often called the "R49 catalyst"):

x=14, y = 29, rule = LifeHistory 3.A$4.2A2$4.A.A$5.A2$5.D2A$6.A.A$6.D2A7$3.A$4.2A2$4.A.A$5.A2$6.2A$3.A .A2.A$.3A.A.2A$A4.A$.3A.A4.2A$3.2A5.A$11.3A$13.A! [[ GRID THUMBNAIL THUMBSIZE 2 ]]

Eater bridge eater

The eater bridge eater catalyst occurs when there is a one cell leading edge of an active region which "activates" the eater bridge (just like with the ship catalyses), with the next generation consisting of a two cell edge for the catalyst to "slam" into. For example:

x=8, y = 9, rule = LifeHistory .A.A$2.A$.C2$2.2A$2.A.A$A.A.3A$2A5.A$6.2A! [[ GRID THUMBNAIL THUMBSIZE 2 ]]

This catalyst also has some uses, like in 30P6.1.

Eater 4

The eater 4 primarily catalyses symmetrical objects. Its most common use is to catalyze a honey farm:

x=14, y = 15, rule = B3/S23 b2o$o2bo5b2o$3o7bo$10bob2o$9b2o2bo$6bo4b2o$6b5o$4b2o4bo$5bo2b2o$5bobo$ o2bobobo$4ob2o$4bo$2bobo$2b2o! [[ GRID THEME 6 THUMBNAIL THUMBSIZE 2 ]]

This can also come in handy sometimes; for example the recently-discovered L122 conduit.

Finding new catalysts

Mike Playle's Bellman is a search program specifically designed to search for new catalysts, given a reaction to be perturbed. It discovered the Snark, as well as many other highly notable patterns. This part of the tutorial hasn't been written yet, so consult the discussion thread and original documentation.

Another catalyst finding program is CatForce, which is a brute force placement program of certain given catalysts in a given area, and can also find transparent catalysts if they're restored quickly enough. It has also discovered quite a few interesting things, like B60.

External links

• The Hunting of the New Herschel Conduits (discussion thread) at the ConwayLife.com forums

• The Hunting of the Elementary Conduits (discussion thread) at the ConwayLife.com forums

• Results of catalyst tests (discussion thread) at the ConwayLife.com forums