Golly is a cross-platform cellular automaton simulator that incorporates hashlife algorithms, allowing it to simulate most Game of Life patterns for astronomical numbers of generations quickly. Version 1.0 was just released, and now also incorporates Python scripting, allowing the construction of astronomically complex patterns via modular high level programming rather than bit-at-a-time copy and pasting.

For instance, here is bricklayer.py, a pattern first found by David Bell in 2002 that is formed by combining two p22 oscillators to make a gun, combining three p22 guns to make a p154 gun, and combining two p154 guns with a p7 glider reflector and a messy small Life pattern called "lumps of muck". By itself, lumps of muck forms two subpatterns that, individually, would themselves turn back into LoM again, but unfortunately interfere with each other creating a mess. The streams of gliders from the two guns and reflector repeatedly hit the back subpattern, creating a block and allowing the other subpattern to grow without interference, effectively pushing the LoM forward diagonally at each step. It ends up forming two long diagonal sequences of blocks, with the guns at one end of the sequence, the LoM on the other, and the gliders running down the middle.

from glife import *

rule ()  # Life

p22_half = pattern("2o$bo$bobo$2b2o3bo$6bob2o$5bo4bo$6bo3bo$7b3o!")
p22 = p22_half + p22_half(26, 9, flip)

gun22 = p22 + p22[1](-18, 11)
gun154 = gun22[27] + gun22[5](49, 12, rcw) + gun22(5, 53, flip_y)

p7_reflector = pattern("""
2b2o5b2o$2b2o5bo$7bobo$7b2o$3b2o$3bobo$4bo3$13bo$10bo2b3o3b2o$3b5o
2b3o3bo2bo$b3obob3o4b2obobo$o4bo4b4obobo2b2o$2ob2ob4o3bobob2obo$
4bobobobobo2bo2bobo$4bobobo2bo2bob3ob2o$3b2obob4o6bobo$7bo4b6o2b
o$9bo2bo2bo4b2o$8b2o!""")
pre_lom = pattern("2bo$2ob2o$2ob2o2$b2ob2o$b2ob2o$3bo!")

all = gun154[210](-52, -38) + gun154[254](52, -38, flip_x) + \
      p7_reflector(8, 23) + pre_lom(-3, 30)

all.display("bricklayer")

And here it is in the previously standard form for such patterns, a run-length-encoded text file:

x = 141, y = 88, rule = 23/3
56bo27bo$54b3o27b3o$53bo33bo$53b2o31b2o3$18b2o6b3o3bobo15bo39bo15bobo
3b3o6b2o$19bo6bobo2bo17bob2o35b2obo17bo2bobo6bo$19bobo6b3o5b2o11bob2o
2b2o27b2o2b2obo11b2o5b3o6bobo$20b2o5bo6bo2bo12bo2bo3bo25bo3bo2bo12bo2b
o6bo5b2o$26bobo7b2o16bobo27bobo16b2o7bobo$25b2o7bobo17bo31bo17bobo7b2o
$25bo2bo6bo5b2o11b2o29b2o11b2o5bo6bo2bo$25b2o5b3o6bobo4bo6bo29bo6bo4bo
bo6b3o5b2o$31bo2bobo6bo4b2o41b2o4bo6bobo2bo$28bobo3b3o6b2o4bo41bo4b2o
6b3o3bobo$9bo14bo22bobo41bobo22bo14bo$2o6bobo11bobo21bo3bo2bo33bo2bo3b
o21bobo11bobo6b2o$bo6bo3b2o9b2o22b2o2b2obo12bo5bo12bob2o2b2o22b2o9b2o
3bo6bo$bobo6b3o5b2o31b2obo10b3o5b3o10bob2o31b2o5b3o6bobo$2b2o5bo7bo2bo
32bo10bo11bo10bo32bo2bo7bo5b2o$7b2o9b2o9bo34b2o9b2o34bo9b2o9b2o$7b2o9b
2o10bo25bo27bo25bo10b2o9b2o$6bo2bo7bo5b2o3b3o18b2o4bo29bo4b2o18b3o3b2o
5bo7bo2bo$7b2o5b3o6bobo24bo4b3o25b3o4bo24bobo6b3o5b2o$13b2o3bo6bo21b3o
10b3o15b3o10b3o21bo6bo3b2o$16bobo6b2o20bo12bob2o2b2o5b2o2b2obo12bo20b
2o6bobo$17bo17bo28bo2bo5bo2bo46bo$33bobo14bo7bo2bobob3o5b3obobo2bo7bo
10bo$34b2o14bobo12bo9bo12bobo9bobo3b2o$50b2o6bo6bo9bo6bo6b2o11bo2bo$
59bo6bo7bo6bo17b2o4bo2bo$40bo19bo6bo5bo6bo19bobo3bobo$41bo3bo14bo19bo
12b2o8bo$39b3o2bo13b3obobo2bo5bo2bobob3o9bobo8bo$44b3o11bo2bo17bo2bo
15b2o$58b2o2b2obo9bob2o2b2o14b3o2b2o$12bo25bo24b3o9b3o17bob2o3b2o24bo$
11bo2bo23b2o56b2obob2o23bo2bo$9bo5bo6bo7b2o5bobo52bo3b2o3bo7b2o7bo6bo
5bo$9bo6bo4bobo6bo60b2obo15bo6bobo4bo6bo$13bo2bo11bobo29b2o17b2o11bo4b
o12bobo11bo2bo$15bobo3bo2bo3b2o31bo17bo13b3ob2ob2o9b2o3bo2bo3bobo$10b
2ob2o2bobo3b2o7b2o24b3o19b3o17b2o5b2o7b2o3bobo2b2ob2o$12b2o3bobo2b2ob
2o6b2o23bo23bo17bo5b2o6b2ob2o2bobo3b2o$7b2o3bo2bo3bobo10bo75bo10bobo3b
o2bo3b2o$6bobo11bo2bo93bo2bo11bobo$6bo6bobo4bo6bo85bo6bo4bobo6bo$5b2o
7bo6bo5bo85bo5bo6bo7b2o$22bo2bo3b3o25bo51b3o3bo2bo$24bo3bob3o15b2o5bob
o33b2o15b3obo3bo$27b3ob3o5b3o6bo7b2o34bo6b3o5b3ob3o$28b2obob2o4b3o4bob
o43bobo4b3o4b2obob2o$28b2obobo6bo5b2o45b2o5bo6bobob2o$29bo4bobo4b2o55b
2o4bobo4bo$30b2o4bobo4bo53bo4bobo4b2o$25b2o5bo6bobob2o51b2obobo6bo5b2o
$24bobo4b3o4b2obob2o51b2obob2o4b3o4bobo$24bo6b3o5b3ob3o49b3ob3o5b3o6bo
$23b2o15b3obo51bob3o15b2o$41b3o28bo24b3o$72bobo$72b2o5$80b2o5b2o$80b2o
5bo$85bobo$85b2o$81b2o$81bobo$82bo$69bo$67b2ob2o$67b2ob2o19bo$88bo2b3o
3b2o$68b2ob2o8b5o2b3o3bo2bo$68b2ob2o6b3obob3o4b2obobo$70bo7bo4bo4b4obo
bo2b2o$78b2ob2ob4o3bobob2obo$82bobobobobo2bo2bobo$82bobobo2bo2bob3ob2o
$81b2obob4o6bobo$85bo4b6o2bo$87bo2bo2bo4b2o$86b2o!

If you want to see the pattern itself within Golly, either one works equally well, but I think you can see which one is more human readable and modifiable as source code.

This is making me think the push-pull replicator-based spaceships that should exist in HighLife and B368/S12578 may be within reach of construction now...