diff --git a/constructs.py b/constructs.py
deleted file mode 100644
index c7d5ce7..0000000
--- a/constructs.py
+++ /dev/null
@@ -1,225 +0,0 @@
-import lifelib
-sess = lifelib.load_rules("b3s23")
-lt = sess.lifetree(n_layers=1)
-
-def minpop(pat):
-    return min(pat[i].population for i in range(pat.period))
-
-rect1 = lt.pattern("""8bo$7bobo$8bo2$6b5o$5bo4bo$4bo2bo$bo2bob2o$obobo5bo$bo2bo4bobo$4b2o2bo
-2bo$9b2o9$17b2o$17b2o8$7b2o22b2o$8bo21bo2bo$5b3o23b2o$5bo6$14b2o$15bo$12b3o$12bo""")
-rect2 = rect1("rot180",52,74)
-grect = lt.pattern("bo$2o$obo")(17,23)
-
-def rectifier_loop(p):
-    if p%4 == 0 or p < 106:
-        return None
-    elif p%4 == 1:
-        n_gliders, mpop = (2, 116) if p >= 133 else (10, 156)
-    elif p%4 == 3:
-        n_gliders, mpop = (6, 136)
-    elif p%8 == 2:
-        n_gliders = 1 if p >= 266 else 5
-        mpop = 113 if p >= 266 else 133 if p >= 210 else None
-    else:
-        n_gliders, mpop = (3, 123 if p >= 206 else None)
-    exts = (p*n_gliders - 266) // 8
-    pat = rect1 + rect2(exts,exts)
-    for _ in range(n_gliders):
-        pat = (pat+grect)[p]
-    return (pat, mpop)
-
-p4b1 = lt.pattern("""14b2o$6bo7bo9bo$6b3o3bobo7b3o$9bob3o7bo$8bob2o9b2o$8bo2bo$17bo$16bobo$
-9bo2bo2bo2bo$10b2o4b2o$b2o$2bo15b2o$2bobo13bobo$3b2o13bo3$7b2o$6bo2bo$
-7bobo$o7bo$3o$3bo$2bo$2bo2bo2b2o$5bo2b2o$3bobo$2bobo$2bo$b2o""")
-p4b2 = lt.pattern("""22b2o$22bo$20bobo$18b2obo$15b6o$15b3o$21b2o$21bo$22b3o$16bo7bo$15bobo$
-15bo2bo$16b2o3$20b2o$20bobo$22bo$22b2o$7b2o4b2o$6bo2bo3b2o$6bobo$7bo6b
-o$14b2o$2b2o12bo$3bo7b2o2bo$3o7bobo3b3o$o9bo7bo$9b2o""")(10,6)
-
-# works down to p36 but fixed oscillators beat it (and it requires more gliders) below p140
-def p4_bumper_loop(p):
-    if p%8 != 4 or p < 140:
-        return None
-    exts = (p-140) // 8
-    return (p4b1 + p4b2(exts,exts), 141)
-
-mold = lt.pattern("3b3o$bob3o$obobo$o2bo$b2o")(-1,15)
-
-def mold_rectifier_loop(p):
-    if p%8 != 4 or p < 212:
-        return None
-    pat, mpop = rectifier_loop(p//2)
-    return (pat+mold, mpop+12 if mpop != None else None)
-
-p8b1 = lt.pattern("""10b2o$10b2o$25bo$23b3o$9b3o10bo$9b2o11b2o$12b2o$11b3o4bo$10bobo4bobo$
-10b2o4bo2bo$17b2o2$3b2o5b2o$4bo5b2o$4bobo$5b2o7bo$9b2ob2o$8bobo2b2o$9b
-o$5bo$4b3o$3bob3o$2bo3bo$bo3bo$3obo$b3o$2bo""")
-p8b2 = lt.pattern("""13bo2b2o$12bo3b2o2b2o$12bo7b2o$13b4o4$12bo$11bobo$11bo2bo$12b2o3$16b2o
-$16bobo$18bo$2o16b2o$2o2b2o$4bobo$5bo$8b3o$2b2o3bo$3bo3bo3bo$3o4bo2bob
-o$o8bobo2bo$10bo3bo$14bo$11b3o""")(14,8)
-
-# works down to p40 but fixed oscillators beat it (and it requires more gliders) below p104
-def p8_loop(p):
-    if p%8 or p < 104:
-        return None
-    exts = p//8 - 13
-    par = exts%2
-    return (p8b1 + p8b2(exts,exts)[4*par], 120+par)
-
-snark1 = lt.pattern("""9b2o$8bobo$2b2o4bo$o2bo2b2ob4o$2obobobobo2bo$3bobobobo$3bobob2o$4bo2$
-17b2o$8b2o7bo$8b2o5bobo$15b2o7$5b2o$6bo$3b3o$3bo""")
-snark2 = snark1("rot90",-20,30)
-snark3 = snark1("rot180",10,50)
-snark4 = snark1("rot270",30,20)
-gsnark = lt.pattern("bo$2o$obo")(7,13)
-
-# only potentially SKOP from p43 to p105 inclusive;
-# at periods divisible by 4 is beaten by fixed oscillators
-def snark_loop(p):
-    mpop = None
-    if not (43 <= p < 106 and p%4):
-        return None
-    elif p%2:
-        n_gliders, mpop = (8, 228)
-        i = (p-37) // 4 if p%4 == 1 else (p-29) // 2 if p <= 75 else (p-79) // 4
-    else:
-        if p >= 58:
-            n_gliders, mpop = (4, 208)
-            i = (p-58) // 4
-        else:
-            n_gliders, mpop = (8, 230)
-            i = (2,3,0)[(p-46)//4]
-    slack = p*n_gliders//8 - 29
-    pat = snark1 + snark2(-i,i) + snark3(slack-2*i,slack) + snark4(slack-i,slack-i)
-    for _ in range(n_gliders):
-        pat = (pat+gsnark)[p]
-    return (pat, mpop)
-
-p6b1 = lt.pattern("4b2o14bo$2o2b2o12b3o$2o2bob2o9bo$5b3o9b2o2$13bo$5b2o5bobo$5b2o4bo2bo$12b2o")
-p6b2 = p6b1("rot90",-2,28)[5]
-p6b3 = p6b1("rot180",26,30)[4]
-p6b4 = p6b1("rot270",28,2)[3]
-gp6b = lt.pattern("2o$obo$o")(14,10)
-
-def p6_bumper_loop(p):
-    if p%6 or not p%8 or p < 36:
-        return None
-    elif p%4:
-        n_gliders, mpop = (2, 122) if p >= 66 else (6, 130)
-        i = (p-30) // 4 if p <= 54 else 0
-    else:
-        n_gliders, mpop = (1, 123) if p >= 132 else (3, 127) if p >= 60 else (5, 140)
-        i = (1,0,3,6)[(p-36)//24] if p <= 108 else 0
-    slack = (p*n_gliders - 124) // 8
-    pat = p6b1 + p6b2(-i,i)[2*i] + p6b3(slack-2*i,slack)[2*slack] + p6b4(slack-i,slack-i)[2*(slack+i)]
-    for _ in range(n_gliders):
-        pat = (pat+gp6b)[p]
-    return (pat, mpop)
-
-pd0_1 = lt.pattern("""16b3o$15bo3bo$15bo3bo$16b3o5$16b3o$15bo3bo$15bo3bo$16b3o4$2o3bo2bo3b2o
-$5o4b5o$2o3bo2bo3b2ob3o$15bo$16bo""")
-pd0_2 = lt.pattern("""6b2o3bo2bo3b2o$6b5o4b5o$6b2o3bo2bo3b2o4$b3o$o3bo$o3bo$b3o5$b3o$o3bo$o
-3bo$b3o""")(11,12)
-
-pd15_1 = lt.pattern("""16b3o$15bo3bo$15bo3bo$16b3o5$16b3o$15bo3bo$15bo3bo$16b3o4$2o3bo2bo3b2o
-$5o4b5o$2o3bo2bo3b2ob3o$15bo$16bo""")
-pd15_2 = lt.pattern("""11b2o$9bo4bo$8bo6bo$7bo8bo$7bo8bo$7bo8bo$8bo6bo$bo7bo4bo$bo9b2o2$bo$ob
-o2$3o3$3o2$obo$bo2$bo$bo""")(14,11)
-# 30+120n: buckaroo shuttle
-pd30_1 = lt.pattern("""o$3o$3bo$2b2o$9b2o$5bo2b2o$4bobo3bo$3bo3bo$3b5o$2b2o3b2o$3b5o$4b3o$5bo
-9$4b2o$4b2o""")
-pd30_2 = lt.pattern("3b2o$3b2o3$3bo$2bobo$bo3bo$b5o$2o3b2o$b5o$2b3o$3bo8$5b2o$5bo$6b3o$8bo")(13,-11)
-
-pd45_1 = lt.pattern("""17bo$17bo$16b3o3$16b3o$17bo$17bo$17bo$17bo$16b3o3$16b3o$17bo$17bo2$2o
-3bo2bo3b2o$5o4b5o$2o3bo2bo3b2ob3o$15bo$16bo""")
-pd45_2 = lt.pattern("""7b2o6b2o$6bo2bo4bo2bo$6bo2bo4bo2bo$6bo2bo4bo2bo$7b2o6b2o4$bo$bo$obo$bo
-$bo$bo$bo$obo$bo$bo""")(18,19)
-# 60+120n: p60 glider shuttle extensions
-pd60_1 = lt.pattern("17b3o$2bo2bo4bo2bo3bo$3o2b6o2b3o2bo$2bo2bo4bo2bo")
-pd60_2 = lt.pattern("2bo2bo4bo2bo$3o2b6o2b3o$2bo2bo4bo2bo")(25,5)
-# 75+120n: 6 bits extensions
-pd75_1 = lt.pattern("""20bo$19bobo3$19b3o$19b3o$20bo3$20bo$19b3o$19b3o3$19bobo$20bo$2b2o6b2o$
-bo2bo4bo2bo4b3o$6o2b6o3bo$bo2bo4bo2bo5bo$2b2o6b2o""")
-pd75_2 = lt.pattern("bo2b2o4b2o2bo$o3b3o2b3o3bo$bo2b2o4b2o2bo")(26,23)
-# 90+120n: Elkies–Simkin 1hd reflector with pentadecathlons (p90 version is Silverstream)
-pd90_1 = lt.pattern("""7b2o4bo$7b2o3bobo$13bo3$2o2b2o2b2o$2o2b2ob2o$9bo3$3b3o$3b3o$4bo$4bo$4b
-o$3bobo3$3bobo$4bo$4bo$4bo$3b3o$3b3o""")
-pd90_2 = lt.pattern("""9b3o$9b3o$10bo$10bo$10bo$9bobo3$9bobo$10bo$10bo$10bo$9b3o$9b3o4$9b2o2b
-2o$9b2o2b2o3$bo$obo3b2o$bo4b2o""")(13,-2)
-
-def pd_shuttle(p):
-    if p%15 or p < 30:
-        return None
-    q = p//15
-    exts, r = divmod(q, 8)
-    exts *= 15
-    if r == 0:
-        return (pd0_1 + pd0_2(exts,exts), 67)
-    elif r == 1:
-        return (pd15_1 + pd15_2(exts,exts), 75)
-    elif r == 2:
-        return (pd30_1 + pd30_2(exts,exts), 51)
-    elif r == 3:
-        return (pd45_1 + pd45_2(exts,exts), 75)
-    elif r == 4:
-        return (pd60_1 + pd60_2(exts,exts), 29)
-    elif r == 5:
-        return (pd75_1 + pd75_2(exts,exts), 49)
-    elif r == 6:
-        return (pd90_1 + pd90_2(exts,exts), 61)
-    else:
-        return None
-
-# 90+24n: Elkies–Simkin 1hd reflector with p6 thumbs (p114 version is Ocellus)
-p6ts1 = lt.pattern("""7b2o4bo$7b2o3bobo$13bo3$2o2b2o2b2o$2o2b2ob2o$9bo3$3b2o$2bo2b2o$2bo4b2o
-$2o3bob2o$bobo$bob6o$2bo5bo$3b3o$5bo""")
-p6ts2 = lt.pattern("""9bo$9b3o$6bo5bo$6b6obo$11bobo$6b2o2bo2b2o$6bobo2b2o$10bobo$11bo4$9b2o
-2b2o$9b2o2b2o3$bo$obo3b2o$bo4b2o""")(13,3)
-
-def p6thumb_shuttle(p):
-    if p%24 != 18 or p < 90:
-        return None
-    return (p6ts1 + p6ts2((p-90)//8, (p-90)//8), 92)
-
-# 98+56n: Elkies–Simkin 1hd reflector with 34P14 shuttles (p98 version is Gallus)
-p14_1 = lt.pattern("""12b2o4bo$12b2o3bobo$18bo3$5b2o2b2o2b2o$5b2o2b2ob2o$14bo3$9bo$8b3o$2o4b
-2o3bob2o$2o4bo2b2o2b2o$6bob2o4$6bob2o$2o4bo2b2o2b2o$2o4b2o3bob2o$8b3o$9bo""")
-p14_2 = lt.pattern("""14bo$13b3o$5b2o4b2o3bob2o$5b2o4bo2b2o2b2o$11bob2o4$11bob2o$5b2o4bo2b2o
-2b2o$5b2o4b2o3bob2o$13b3o$14bo4$9b2o2b2o$9b2o2b2o3$bo$obo3b2o$bo4b2o""")(19,0)
-
-def p14_shuttle(p):
-    if p%56 != 42 or p < 98:
-        return None
-    return (p14_1 + p14_2((p-98)//8, (p-98)//8), 105)
-
-# 184+92n: Hickerson's stop-and-go reaction
-tbs0_1 = lt.pattern("""2b2o5b2o$2b2o5b2o6$2b3o3b3o$bo2bo3bo2bo$bo3bobo3bo$2obobobobob2o$2ob2o
-3b2ob2o$b3o5b3o6$3bo$2bobo$bo3bo$b5o$obobobo$bo3bo2$bo3bo$obobobo$b5o
-3b2o$bo3bo3b2o$2bobo$3bo2$2b3o$2bo$3bo""")
-tbs0_2 = lt.pattern("""19b2o$18b5o$2b2o14bo4bo5b2o$2b2o14b3o2bo5b2o$19bo2b2o$20b2o$4bo3bo$2b
-2obobob2o9b2o$bob2o3b2obo7bo2b2o$o2bo5bo2bo5b3o2bo5b2o$bob2o3b2obo6bo
-4bo5b2o$2b2obobob2o7b5o$4bo3bo10b2o""")(-8,10)
-tbs92_2 = lt.pattern("""9bo$8bobo$2b2o3bo3bo$2b2o3b5o$6bobobobo$7bo3bo2$7bo3bo$6bobobobo$7b5o$
-7bo3bo$8bobo$9bo6$b3o5b3o$2ob2o3b2ob2o$2obobobobob2o$bo3bobo3bo$bo2bo
-3bo2bo$2b3o3b3o6$2b2o$2b2o""")(-8,33)
-
-# 138+184n: jslife reflectors-180.lif, 5hd class 1
-tbs138_1 = lt.pattern("""b2o5b2o$b2o5b2o13$bo7bo$obo5bobo$3bo3bo$o2bo3bo2bo$bobo3bobo$3b2ob2o$
-2ob2ob2ob2o$2o2bobo2b2o$b3o3b3o2b3o$2bo5bo3bo$13bo3$b2o$b2o""")
-tbs138_2 = lt.pattern("""3bo$2bobo2$o5bo2b2o$3bo5b2o$2o3b2o4$2o3b2o$3bo$o5bo2$2bobo$3bo3$2bo7bo
-$bobo5bobo$4bo3bo$bo2bo3bo2bo$2bobo3bobo$4b2ob2o$b2ob2ob2ob2o$b2o2bobo
-2b2o$2b3o3b3o$3bo5bo4$2b2o5b2o$2b2o5b2o""")(21,25)
-
-def twinbees_shuttle(p):
-    if p%46 or p < 138:
-        return None
-    q = p//46
-    exts, r = divmod(q, 4)
-    exts *= 23
-    if r == 0:
-        return (tbs0_1 + tbs0_2(exts,exts), 60)
-    elif r == 2:
-        return (tbs0_1 + tbs92_2(exts,exts), 77)
-    elif r == 3:
-        return (tbs138_1 + tbs138_2(exts,exts), 72)
-    else:
-        return None
diff --git a/readme.md b/readme.md
index 995b1f2..a6f6c9a 100644
--- a/readme.md
+++ b/readme.md
@@ -4,7 +4,7 @@ In May and June 2021 David Raucci (hotdogPi) on the ConwayLife forums discovered
 
 This repository started out as an independent script in my glider synthesis database [Shinjuku](https://gitlab.com/parclytaxel/Shinjuku) as an automatic generator of the aforementioned glider loops and collector of other **s**mallest **k**nown **o**scillators of **p**eriods _n_ – hence the name Skopje, North Macedonia's capital. It still requires [lifelib](https://gitlab.com/apgoucher/lifelib) however.
 
-To get the smallest known oscillator of period 109 together with its minimum population:
+To get the smallest known oscillator of period 109 in Conway's Life together with its minimum population:
 
 ```python
 from skopje import skop
@@ -13,4 +13,8 @@ skop109, minpop109 = skop(109)[0]
 
 `skop()` returns a _list_ of pairs (lifelib Pattern, minimum population) to allow ties as in the p4, p7 and p92 cases; to get the pattern's apgcode and RLE use `skop109.apgcode` and `skop109.rle_string()` respectively. The function compares several different constructions as well as a list of fixed oscillators, LCM or otherwise, to arrive at its final result.
 
-Each function producing oscillators of a certain type for an infinite number of periods should accept the desired period as its argument and return `None` if the construction is not applicable to that period or (Pattern, minimum population) otherwise. The latter element can itself be `None` to indicate that the period is in a range where the population cannot easily be calculated.
+SKOPs in other rules can be found by passing the `rule=` argument; the supplied string gets run through lifelib's `sanirule()` function before being mapped to a filename. The file itself should contain three objects:
+
+* `lt`, the lifetree under which computations are performed.
+* `fixeds`, a multiline string where each line gives the period of a fixed oscillator, its apgcode and its minimum population, all separated by spaces.
+* `cfuncs`, a sequence of functions each accepting a period and returning `None` if its corresponding construction is not applicable to that period or (Pattern, minimum population) otherwise. The latter element can itself be `None` to indicate that the period is in a range where the population does not follow a defined formula.
diff --git a/skopje.py b/skopje.py
deleted file mode 100755
index 16688bf..0000000
--- a/skopje.py
+++ /dev/null
@@ -1,35 +0,0 @@
-from constructs import *
-
-def read_oscfiles(*fns):
-    """Read oscillators and their minimum populations from provided files
-    and return a dictionary."""
-    res = {}
-    for fn in fns:
-        with open(fn, 'r') as f:
-            for l in f:
-                period, apgcode, mpop = l.split()
-                period = int(period)
-                res[period] = res.get(period, tuple()) + ((lt.pattern(apgcode), int(mpop)),)
-    return res
-
-def skop(p):
-    """Return a list of pairs (Pattern, minimum population) representing
-    the smallest known oscillators of the specified period."""
-    fixed = read_oscfiles("fixedoscs")
-    cands = list(fixed.get(p, []))
-    cands.append(rectifier_loop(p))
-    cands.append(mold_rectifier_loop(p))
-    cands.append(p4_bumper_loop(p))
-    cands.append(p8_loop(p))
-    cands.append(snark_loop(p))
-    cands.append(p6_bumper_loop(p))
-    cands.append(pd_shuttle(p))
-    cands.append(p6thumb_shuttle(p))
-    cands.append(p14_shuttle(p))
-    cands.append(twinbees_shuttle(p))
-    cands = list(filter(bool, cands))
-    if not cands:
-        return []
-    cands = [pair if pair[1] else (pair[0], minpop(pair[0])) for (i, pair) in enumerate(cands)]
-    mp = min(pair[1] for pair in cands)
-    return list(filter(lambda pair: pair[1] == mp, cands))
diff --git a/skopje/__init__.py b/skopje/__init__.py
new file mode 100644
index 0000000..dcefb0e
--- /dev/null
+++ b/skopje/__init__.py
@@ -0,0 +1,2 @@
+# What to do upon calling "import skopje"
+from .skop import skop
diff --git a/fixedoscs b/skopje/life.py
similarity index 52%
rename from fixedoscs
rename to skopje/life.py
index d041652..93a3834 100644
--- a/fixedoscs
+++ b/skopje/life.py
@@ -1,4 +1,8 @@
-1 xs4_33 4
+import lifelib
+sess = lifelib.load_rules("b3s23")
+lt = sess.lifetree(n_layers=1)
+
+fixeds = """1 xs4_33 4
 1 xs4_252 4
 2 xp2_7 3
 3 xp3_4hh186z07 12
@@ -138,4 +142,226 @@
 512 xp512_yr33y166z0ggy033y16426ye33y0ccz011w66yuggz66yz56zzzy2mqyz66zygckgk2a21ya66woozy133y0ccye6426y1cczy566y1cc 100
 576 xp576_y32560652y92560652zy03diiie0eiiid3y33diiie0eiiid3zyboozzykgk34zooyj16w6y5oozz33y5cwcgyj33zy94o51zzyk33zy0om999e0e999moy3om999e0e999mozy38kc0ck8y98kc0ck8 184
 690 xp690_0ooy9vtvzyc757zok4sxs4kozzzz033y133 40
-1008 xp1008_y48oyc356zy432yi696y9o8gozyjc871zzy12552yg2bq4y4o8zca6y3oggyp113y3ca6zy823ys8kk8zzyogs26zx3123y9cicyi8ozymckoyc32 107
+1008 xp1008_y48oyc356zy432yi696y9o8gozyjc871zzy12552yg2bq4y4o8zca6y3oggyp113y3ca6zy823ys8kk8zzyogs26zx3123y9cicyi8ozymckoyc32 107"""
+
+rect1 = lt.pattern("""8bo$7bobo$8bo2$6b5o$5bo4bo$4bo2bo$bo2bob2o$obobo5bo$bo2bo4bobo$4b2o2bo
+2bo$9b2o9$17b2o$17b2o8$7b2o22b2o$8bo21bo2bo$5b3o23b2o$5bo6$14b2o$15bo$12b3o$12bo""")
+rect2 = rect1("rot180",52,74)
+grect = lt.pattern("bo$2o$obo")(17,23)
+
+def rectifier_loop(p):
+    if p%4 == 0 or p < 106:
+        return None
+    elif p%4 == 1:
+        n_gliders, mpop = (2, 116) if p >= 133 else (10, 156)
+    elif p%4 == 3:
+        n_gliders, mpop = (6, 136)
+    elif p%8 == 2:
+        n_gliders = 1 if p >= 266 else 5
+        mpop = 113 if p >= 266 else 133 if p >= 210 else None
+    else:
+        n_gliders, mpop = (3, 123 if p >= 206 else None)
+    exts = (p*n_gliders - 266) // 8
+    pat = rect1 + rect2(exts,exts)
+    for _ in range(n_gliders):
+        pat = (pat+grect)[p]
+    return (pat, mpop)
+
+p4b1 = lt.pattern("""14b2o$6bo7bo9bo$6b3o3bobo7b3o$9bob3o7bo$8bob2o9b2o$8bo2bo$17bo$16bobo$
+9bo2bo2bo2bo$10b2o4b2o$b2o$2bo15b2o$2bobo13bobo$3b2o13bo3$7b2o$6bo2bo$
+7bobo$o7bo$3o$3bo$2bo$2bo2bo2b2o$5bo2b2o$3bobo$2bobo$2bo$b2o""")
+p4b2 = lt.pattern("""22b2o$22bo$20bobo$18b2obo$15b6o$15b3o$21b2o$21bo$22b3o$16bo7bo$15bobo$
+15bo2bo$16b2o3$20b2o$20bobo$22bo$22b2o$7b2o4b2o$6bo2bo3b2o$6bobo$7bo6b
+o$14b2o$2b2o12bo$3bo7b2o2bo$3o7bobo3b3o$o9bo7bo$9b2o""")(10,6)
+
+# works down to p36 but fixed oscillators beat it (and it requires more gliders) below p140
+def p4_bumper_loop(p):
+    if p%8 != 4 or p < 140:
+        return None
+    exts = (p-140) // 8
+    return (p4b1 + p4b2(exts,exts), 141)
+
+mold = lt.pattern("3b3o$bob3o$obobo$o2bo$b2o")(-1,15)
+
+def mold_rectifier_loop(p):
+    if p%8 != 4 or p < 212:
+        return None
+    pat, mpop = rectifier_loop(p//2)
+    return (pat+mold, mpop+12 if mpop != None else None)
+
+p8b1 = lt.pattern("""10b2o$10b2o$25bo$23b3o$9b3o10bo$9b2o11b2o$12b2o$11b3o4bo$10bobo4bobo$
+10b2o4bo2bo$17b2o2$3b2o5b2o$4bo5b2o$4bobo$5b2o7bo$9b2ob2o$8bobo2b2o$9b
+o$5bo$4b3o$3bob3o$2bo3bo$bo3bo$3obo$b3o$2bo""")
+p8b2 = lt.pattern("""13bo2b2o$12bo3b2o2b2o$12bo7b2o$13b4o4$12bo$11bobo$11bo2bo$12b2o3$16b2o
+$16bobo$18bo$2o16b2o$2o2b2o$4bobo$5bo$8b3o$2b2o3bo$3bo3bo3bo$3o4bo2bob
+o$o8bobo2bo$10bo3bo$14bo$11b3o""")(14,8)
+
+# works down to p40 but fixed oscillators beat it (and it requires more gliders) below p104
+def p8_loop(p):
+    if p%8 or p < 104:
+        return None
+    exts = p//8 - 13
+    par = exts%2
+    return (p8b1 + p8b2(exts,exts)[4*par], 120+par)
+
+snark1 = lt.pattern("""9b2o$8bobo$2b2o4bo$o2bo2b2ob4o$2obobobobo2bo$3bobobobo$3bobob2o$4bo2$
+17b2o$8b2o7bo$8b2o5bobo$15b2o7$5b2o$6bo$3b3o$3bo""")
+snark2 = snark1("rot90",-20,30)
+snark3 = snark1("rot180",10,50)
+snark4 = snark1("rot270",30,20)
+gsnark = lt.pattern("bo$2o$obo")(7,13)
+
+# only potentially SKOP from p43 to p105 inclusive;
+# at periods divisible by 4 is beaten by fixed oscillators
+def snark_loop(p):
+    mpop = None
+    if not (43 <= p < 106 and p%4):
+        return None
+    elif p%2:
+        n_gliders, mpop = (8, 228)
+        i = (p-37) // 4 if p%4 == 1 else (p-29) // 2 if p <= 75 else (p-79) // 4
+    else:
+        if p >= 58:
+            n_gliders, mpop = (4, 208)
+            i = (p-58) // 4
+        else:
+            n_gliders, mpop = (8, 230)
+            i = (2,3,0)[(p-46)//4]
+    slack = p*n_gliders//8 - 29
+    pat = snark1 + snark2(-i,i) + snark3(slack-2*i,slack) + snark4(slack-i,slack-i)
+    for _ in range(n_gliders):
+        pat = (pat+gsnark)[p]
+    return (pat, mpop)
+
+p6b1 = lt.pattern("4b2o14bo$2o2b2o12b3o$2o2bob2o9bo$5b3o9b2o2$13bo$5b2o5bobo$5b2o4bo2bo$12b2o")
+p6b2 = p6b1("rot90",-2,28)[5]
+p6b3 = p6b1("rot180",26,30)[4]
+p6b4 = p6b1("rot270",28,2)[3]
+gp6b = lt.pattern("2o$obo$o")(14,10)
+
+def p6_bumper_loop(p):
+    if p%6 or not p%8 or p < 36:
+        return None
+    elif p%4:
+        n_gliders, mpop = (2, 122) if p >= 66 else (6, 130)
+        i = (p-30) // 4 if p <= 54 else 0
+    else:
+        n_gliders, mpop = (1, 123) if p >= 132 else (3, 127) if p >= 60 else (5, 140)
+        i = (1,0,3,6)[(p-36)//24] if p <= 108 else 0
+    slack = (p*n_gliders - 124) // 8
+    pat = p6b1 + p6b2(-i,i)[2*i] + p6b3(slack-2*i,slack)[2*slack] + p6b4(slack-i,slack-i)[2*(slack+i)]
+    for _ in range(n_gliders):
+        pat = (pat+gp6b)[p]
+    return (pat, mpop)
+
+pd0_1 = lt.pattern("""16b3o$15bo3bo$15bo3bo$16b3o5$16b3o$15bo3bo$15bo3bo$16b3o4$2o3bo2bo3b2o
+$5o4b5o$2o3bo2bo3b2ob3o$15bo$16bo""")
+pd0_2 = lt.pattern("""6b2o3bo2bo3b2o$6b5o4b5o$6b2o3bo2bo3b2o4$b3o$o3bo$o3bo$b3o5$b3o$o3bo$o
+3bo$b3o""")(11,12)
+
+pd15_1 = lt.pattern("""16b3o$15bo3bo$15bo3bo$16b3o5$16b3o$15bo3bo$15bo3bo$16b3o4$2o3bo2bo3b2o
+$5o4b5o$2o3bo2bo3b2ob3o$15bo$16bo""")
+pd15_2 = lt.pattern("""11b2o$9bo4bo$8bo6bo$7bo8bo$7bo8bo$7bo8bo$8bo6bo$bo7bo4bo$bo9b2o2$bo$ob
+o2$3o3$3o2$obo$bo2$bo$bo""")(14,11)
+# 30+120n: buckaroo shuttle
+pd30_1 = lt.pattern("""o$3o$3bo$2b2o$9b2o$5bo2b2o$4bobo3bo$3bo3bo$3b5o$2b2o3b2o$3b5o$4b3o$5bo
+9$4b2o$4b2o""")
+pd30_2 = lt.pattern("3b2o$3b2o3$3bo$2bobo$bo3bo$b5o$2o3b2o$b5o$2b3o$3bo8$5b2o$5bo$6b3o$8bo")(13,-11)
+
+pd45_1 = lt.pattern("""17bo$17bo$16b3o3$16b3o$17bo$17bo$17bo$17bo$16b3o3$16b3o$17bo$17bo2$2o
+3bo2bo3b2o$5o4b5o$2o3bo2bo3b2ob3o$15bo$16bo""")
+pd45_2 = lt.pattern("""7b2o6b2o$6bo2bo4bo2bo$6bo2bo4bo2bo$6bo2bo4bo2bo$7b2o6b2o4$bo$bo$obo$bo
+$bo$bo$bo$obo$bo$bo""")(18,19)
+# 60+120n: p60 glider shuttle extensions
+pd60_1 = lt.pattern("17b3o$2bo2bo4bo2bo3bo$3o2b6o2b3o2bo$2bo2bo4bo2bo")
+pd60_2 = lt.pattern("2bo2bo4bo2bo$3o2b6o2b3o$2bo2bo4bo2bo")(25,5)
+# 75+120n: 6 bits extensions
+pd75_1 = lt.pattern("""20bo$19bobo3$19b3o$19b3o$20bo3$20bo$19b3o$19b3o3$19bobo$20bo$2b2o6b2o$
+bo2bo4bo2bo4b3o$6o2b6o3bo$bo2bo4bo2bo5bo$2b2o6b2o""")
+pd75_2 = lt.pattern("bo2b2o4b2o2bo$o3b3o2b3o3bo$bo2b2o4b2o2bo")(26,23)
+# 90+120n: Elkies–Simkin 1hd reflector with pentadecathlons (p90 version is Silverstream)
+pd90_1 = lt.pattern("""7b2o4bo$7b2o3bobo$13bo3$2o2b2o2b2o$2o2b2ob2o$9bo3$3b3o$3b3o$4bo$4bo$4b
+o$3bobo3$3bobo$4bo$4bo$4bo$3b3o$3b3o""")
+pd90_2 = lt.pattern("""9b3o$9b3o$10bo$10bo$10bo$9bobo3$9bobo$10bo$10bo$10bo$9b3o$9b3o4$9b2o2b
+2o$9b2o2b2o3$bo$obo3b2o$bo4b2o""")(13,-2)
+
+def pd_shuttle(p):
+    if p%15 or p < 30:
+        return None
+    q = p//15
+    exts, r = divmod(q, 8)
+    exts *= 15
+    if r == 0:
+        return (pd0_1 + pd0_2(exts,exts), 67)
+    elif r == 1:
+        return (pd15_1 + pd15_2(exts,exts), 75)
+    elif r == 2:
+        return (pd30_1 + pd30_2(exts,exts), 51)
+    elif r == 3:
+        return (pd45_1 + pd45_2(exts,exts), 75)
+    elif r == 4:
+        return (pd60_1 + pd60_2(exts,exts), 29)
+    elif r == 5:
+        return (pd75_1 + pd75_2(exts,exts), 49)
+    elif r == 6:
+        return (pd90_1 + pd90_2(exts,exts), 61)
+    else:
+        return None
+
+# 90+24n: Elkies–Simkin 1hd reflector with p6 thumbs (p114 version is Ocellus)
+p6ts1 = lt.pattern("""7b2o4bo$7b2o3bobo$13bo3$2o2b2o2b2o$2o2b2ob2o$9bo3$3b2o$2bo2b2o$2bo4b2o
+$2o3bob2o$bobo$bob6o$2bo5bo$3b3o$5bo""")
+p6ts2 = lt.pattern("""9bo$9b3o$6bo5bo$6b6obo$11bobo$6b2o2bo2b2o$6bobo2b2o$10bobo$11bo4$9b2o
+2b2o$9b2o2b2o3$bo$obo3b2o$bo4b2o""")(13,3)
+
+def p6thumb_shuttle(p):
+    if p%24 != 18 or p < 90:
+        return None
+    return (p6ts1 + p6ts2((p-90)//8, (p-90)//8), 92)
+
+# 98+56n: Elkies–Simkin 1hd reflector with 34P14 shuttles (p98 version is Gallus)
+p14_1 = lt.pattern("""12b2o4bo$12b2o3bobo$18bo3$5b2o2b2o2b2o$5b2o2b2ob2o$14bo3$9bo$8b3o$2o4b
+2o3bob2o$2o4bo2b2o2b2o$6bob2o4$6bob2o$2o4bo2b2o2b2o$2o4b2o3bob2o$8b3o$9bo""")
+p14_2 = lt.pattern("""14bo$13b3o$5b2o4b2o3bob2o$5b2o4bo2b2o2b2o$11bob2o4$11bob2o$5b2o4bo2b2o
+2b2o$5b2o4b2o3bob2o$13b3o$14bo4$9b2o2b2o$9b2o2b2o3$bo$obo3b2o$bo4b2o""")(19,0)
+
+def p14_shuttle(p):
+    if p%56 != 42 or p < 98:
+        return None
+    return (p14_1 + p14_2((p-98)//8, (p-98)//8), 105)
+
+# 184+92n: Hickerson's stop-and-go reaction
+tbs0_1 = lt.pattern("""2b2o5b2o$2b2o5b2o6$2b3o3b3o$bo2bo3bo2bo$bo3bobo3bo$2obobobobob2o$2ob2o
+3b2ob2o$b3o5b3o6$3bo$2bobo$bo3bo$b5o$obobobo$bo3bo2$bo3bo$obobobo$b5o
+3b2o$bo3bo3b2o$2bobo$3bo2$2b3o$2bo$3bo""")
+tbs0_2 = lt.pattern("""19b2o$18b5o$2b2o14bo4bo5b2o$2b2o14b3o2bo5b2o$19bo2b2o$20b2o$4bo3bo$2b
+2obobob2o9b2o$bob2o3b2obo7bo2b2o$o2bo5bo2bo5b3o2bo5b2o$bob2o3b2obo6bo
+4bo5b2o$2b2obobob2o7b5o$4bo3bo10b2o""")(-8,10)
+tbs92_2 = lt.pattern("""9bo$8bobo$2b2o3bo3bo$2b2o3b5o$6bobobobo$7bo3bo2$7bo3bo$6bobobobo$7b5o$
+7bo3bo$8bobo$9bo6$b3o5b3o$2ob2o3b2ob2o$2obobobobob2o$bo3bobo3bo$bo2bo
+3bo2bo$2b3o3b3o6$2b2o$2b2o""")(-8,33)
+
+# 138+184n: jslife reflectors-180.lif, 5hd class 1
+tbs138_1 = lt.pattern("""b2o5b2o$b2o5b2o13$bo7bo$obo5bobo$3bo3bo$o2bo3bo2bo$bobo3bobo$3b2ob2o$
+2ob2ob2ob2o$2o2bobo2b2o$b3o3b3o2b3o$2bo5bo3bo$13bo3$b2o$b2o""")
+tbs138_2 = lt.pattern("""3bo$2bobo2$o5bo2b2o$3bo5b2o$2o3b2o4$2o3b2o$3bo$o5bo2$2bobo$3bo3$2bo7bo
+$bobo5bobo$4bo3bo$bo2bo3bo2bo$2bobo3bobo$4b2ob2o$b2ob2ob2ob2o$b2o2bobo
+2b2o$2b3o3b3o$3bo5bo4$2b2o5b2o$2b2o5b2o""")(21,25)
+
+def twinbees_shuttle(p):
+    if p%46 or p < 138:
+        return None
+    q = p//46
+    exts, r = divmod(q, 4)
+    exts *= 23
+    if r == 0:
+        return (tbs0_1 + tbs0_2(exts,exts), 60)
+    elif r == 2:
+        return (tbs0_1 + tbs92_2(exts,exts), 77)
+    elif r == 3:
+        return (tbs138_1 + tbs138_2(exts,exts), 72)
+    else:
+        return None
+
+cfuncs = (rectifier_loop, mold_rectifier_loop, p4_bumper_loop, p8_loop, snark_loop,
+          p6_bumper_loop, pd_shuttle, p6thumb_shuttle, p14_shuttle, twinbees_shuttle)
diff --git a/skopje/skop.py b/skopje/skop.py
new file mode 100755
index 0000000..eea3391
--- /dev/null
+++ b/skopje/skop.py
@@ -0,0 +1,30 @@
+from importlib import import_module
+from lifelib.genera import sanirule
+
+aliases = {"b3s23": "life"}
+
+def minpop(pat):
+    """Compute the minimum population of the given pattern.
+    Because the latter is already associated with a rule no
+    further arguments are required."""
+    return min(pat[i].population for i in range(pat.period))
+
+def skop(p, rule="b3s23"):
+    """Return a list of pairs (Pattern, minimum population) representing
+    the smallest known oscillators of the specified period in the given rule.
+    Assumes that the local installation of lifelib knows about said rule."""
+    rule = sanirule(rule)
+    rmod = import_module(f"..{aliases.get(rule, rule)}", __name__)
+    cands = []
+    for line in rmod.fixeds.split("\n"):
+        lp, apg, mp = line.split()
+        if int(lp) == p:
+            cands.append((rmod.lt.pattern(apg), int(mp)))
+    for cfunc in rmod.cfuncs:
+        cands.append(cfunc(p))
+    cands = list(filter(bool, cands))
+    if not cands:
+        return []
+    cands = [pair if pair[1] else (pair[0], minpop(pair[0])) for (i, pair) in enumerate(cands)]
+    mp = min(pair[1] for pair in cands)
+    return list(filter(lambda pair: pair[1] == mp, cands))
diff --git a/skopje/symbiosis.py b/skopje/symbiosis.py
new file mode 100644
index 0000000..6708be0
--- /dev/null
+++ b/skopje/symbiosis.py
@@ -0,0 +1,353 @@
+import lifelib
+sess = lifelib.load_rules("xsymbiosis")
+lt = sess.lifetree()
+
+fixeds = """1 xs2_1_2 2
+2 xp2_7 3
+3 xp3_f_g 5
+4 xp4_ic_1z1 6
+5 xp5_ci_1z1 6
+6 xp6_2we4_1y0a 7
+7 xp7_usz1_1z2 7
+8 xp8_acs_1zw1 7
+9 xp9_02b7_28 7
+10 xp10_61e_1 7
+11 xp11_02s_21z01 7
+12 xp12_22go_1zx1 7
+13 xp13_oez1_018z02 9
+14 xp14_02208c_410g 8
+15 xp15_02b4_4g 7
+16 xp16_2og_01z1 6
+17 xp17_043h_8hzw1 9
+18 xp18_ka4_w12z1 8
+19 xp19_9312_g04 8
+20 xp20_iem_1z01 8
+21 xp21_028s_1zw1 7
+22 xp22_028e_4g1 7
+23 xp23_2g0cc_1y0gz1 8
+24 xp24_030186_2y14 8
+25 xp25_2cq8_1w2o 10
+26 xp26_2k6z1_g1 8
+27 xp27_05126z01_5g 8
+28 xp28_0224c_14xg 8
+29 xp29_012413_2w8w1 9
+30 xp30_1gee_21 9
+31 xp31_01j84zg_x18z0g 10
+32 xp32_03104_2xgo 8
+33 xp33_0273c_1y0a 10
+34 xp34_2gozwg_1wgz08 8
+35 xp35_031zxe43_4y1gzy0g 11
+36 xp36_0d1i_izw1 9
+37 xp37_2oo_1wk 8
+38 xp38_024e_18g 8
+39 xp39_o428g_21z1x23 12
+40 xp40_21w6571_14w8x1 12
+41 xp41_0gqw8_w1x4z1 8
+42 xp42_03ho_1xg 8
+43 xp43_0i974_1y04z1 9
+44 xp44_cquz02_01z1 11
+45 xp45_0222484_201w2 9
+46 xp46_01z039w8_w2z3wg0g 11
+47 xp47_023h6_1xg2 10
+48 xp48_6kz02_018z2 8
+49 xp49_w8acz1_081w2z2 10
+50 xp50_09glfw2_9y16 12
+51 xp51_0gk2zy32_w1z1y21 8
+52 xp52_620fx8_10gy166 13
+53 xp53_4g028zx2297_8w104z104x8 16
+54 xp54_020gzxh54wg_41zx2gx8 13
+55 xp55_079czw1_1g 10
+56 xp56_01408d32_208x402 13
+57 xp57_03bozw1y02_1gzy21 11
+58 xp58_ws33gsg04z1_g01x208 15
+59 xp59_25b30g_8gzy21 12
+60 xp60_0139y28_140ggy04 11
+61 xp61_27az2_x4z1 9
+62 xp62_14e6o_2y08 10
+63 xp63_4a97_h 10
+64 xp64_1318_40g 7
+65 xp65_01b4zy81_1gy5g 9
+66 xp66_01a4x8_1gy04 8
+67 xp67_0lvz31_x9z4021 15
+68 xp68_02sozg_w10oz8 11
+69 xp69_08xge6w1zx4_8y3802zw2x1 13
+70 xp70_xg88m8z041_y04w16za1 16
+71 xp71_01z08y2801zx2314_w1z4y2801zw4x84 15
+72 xp72_qf1_w82z1 10
+73 xp73_iz13ek_1agzx18zw1 15
+74 xp74_02bja4_1y0g4 10
+75 xp75_y31z0evzx1_0gy02zkz012 16
+76 xp76_010g8gz4ehrgfy18zx1zy8okc_2g84zy23xg 30
+77 xp77_044172c_4w8wg4 13
+78 xp78_y18048sicz1_y1402w1z2 13
+79 xp79_gs6kz01z41_w10az2z3 14
+80 xp80_g0588cz0kgf7_0g2zkxgz1 21
+81 xp81_02y0648gzy2gg843z01y01_2y21248zy5g81z1y221 25
+82 xp82_08026z040gox1_401z8y21zw1 14
+83 xp83_0o4226z0f8_g2w1z2 16
+84 xp84_ohgzb0iz01_160gz0k 16
+85 xp85_18ogs2ux1_2hy1gx1 15
+86 xp86_08zy06d132_8y633zy1gx2 14
+87 xp87_1c22ey64_g1ggy64 12
+88 xp88_0g0842zxa7aw8a_g04x1zx4xg 19
+89 xp89_06208bk8z4c_01xgw4z0g2 17
+90 xp90_1ggzwh54_01zw2g 11
+91 xp91_g1z178ge4_02z2gxg8 16
+92 xp92_0212gozwg_1x10gzw8 11
+93 xp93_0106aicy5g_108gy78zy11 15
+94 xp94_0cdw5zx1_2w1w2zw2 12
+95 xp95_0315963_208x41 15
+96 xp96_0o46z63_k21z8 13
+97 xp97_0351e4_408wg2 13
+98 xp98_0gy2108z0348_gy220gz08g 12
+99 xp99_020ksg8y28_1y04y48 12
+100 xp100_1y18066zwgw6b_2y0401w4zy2g4z01 18
+101 xp101_060oo273y02_21gxokx1zx1 21
+102 xp102_01e16c4_24wgw4 13
+103 xp103_wdiszg28j_05gz8g1zx1 20
+104 xp104_02so_1x4c 9
+105 xp105_0g0ks81_gx22zzx8k8 14
+106 xp106_029qwgz02zx8_2x2wgz2zxg 14
+107 xp107_0igz8m5_014zg085z1 16
+108 xp108_4y3q8gz26y29_8y31w8zogy1802 17
+109 xp109_02phby24_2y08y18zx1 14
+110 xp110_4g0s9zz01_802w2zz1 12
+111 xp111_010os21364_20gx4w12 17
+113 xp113_a0ehvh_hw4 17
+114 xp114_08sir204z0c_421x58 18
+115 xp115_0g0g01z0fgvp6_w8wg2z2 18
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+
+m0small_1 = lt.pattern("11.A$11.B$7.A$6.B2A$AB2$6.A$2.2A2.A.A$2.2A2.2A$3.B")
+m0small_2 = lt.pattern("8.B$8.2A$8.2A3$10.BA$3.2AB$3.2A$B$A")(4,6)
+
+m0_1 = lt.pattern("13.2B$2B9.2A.B$B10.2A$.2A$.2A")
+m0_2 = lt.pattern("12.A$12.A$12.2A2$13.A$2.2A10.B$B.2A9.2B$2B")(1,8)
+
+m1_1 = lt.pattern("12.A$12.B$8.A$7.B2A2$AB$7.A$7.A.A$2.2A3.2A$2.2A$3.B")
+m1_2 = lt.pattern("9.2A$9.2AB3$8.A$8.B$3.2AB$3.2A$B$A")(5,8)
+
+m2small_1 = lt.pattern("5.B$A4.2A$B5.A2$A3.A$2A4.A$B5.A$3.A.2A")
+m2small_2 = lt.pattern("6.B$5.2A$5.2A2$2A4.B$2A4.A$.B")(6,6)
+
+m2_1 = lt.pattern("2.2B$2.B$3.2A$B3.A$.3A2$.B$2.AB")
+m2_2 = lt.pattern("BA$2.B2$2.A$2A.B$A$.B$2B")(16,1)
+
+m3_1 = lt.pattern("13.A$13.B$9.2A$8.B2A3$3.B$3.A3$B2A$.2A")
+m3_2 = lt.pattern("9.A$9.A$9.2A2$10.A$11.B$10.2B$3.2AB$3.2A$B$A")(4,9)
+
+m4_1 = lt.pattern("13.A$13.B$9.2A$8.B2A3$3.B$3.A3$B2A$.2A")
+m4_2 = lt.pattern("10.A$10.A$10.2A2$11.A$12.B$BA9.2B$4.2A$4.2A$4.B")(3,9)
+
+m5_1 = lt.pattern("10.B$9.2A$9.2A$13.AB2$3.B$3.A3$B2A$.2A")
+m5_2 = lt.pattern("10.A$10.A$10.2A2$11.A$12.B$BA9.2B$4.2A$4.2A$4.B")(4,9)
+
+m6_1 = lt.pattern("8.B$7.2A$7.2A$2B9.AB$B$.2A$.2A")
+m6_2 = lt.pattern("10.A$10.A$10.2A2$11.A$12.B$BA9.2B$4.2A$4.2A$4.B")(2,9)
+
+m7_1 = lt.pattern("13.2B$2B9.2A.B$B10.2A$.2A$.2A")
+m7_2 = lt.pattern("10.A$10.A$10.2A2$11.A$12.B$BA9.2B$4.2A$4.2A$4.B")(3,8)
+
+def universal_reflector_loop(p):
+    n, r = divmod(p, 8)
+    if r == 0:
+        if p < 56:
+            return None
+        elif p < 144:
+            return (m0small_1 + m0small_2(n-7,n-7), 32)
+        return (m0_1 + m0_2(n-18,n-18), 29)
+    elif r == 1:
+        if p < 65:
+            return None
+        return (m1_1 + m1_2(n-8,n-8), 32)
+    elif r == 2:
+        # there's a p18+8n shuttle akin to Elkies's Life reflector,
+        # but it's always beaten by fixed oscillators before p106
+        if p < 106:
+            return None
+        return (m2_1 + m2_2(n-13,n-13), 24)
+    elif r == 3:
+        if p < 91:
+            return None
+        return (m3_1 + m3_2(n-11,n-11), 29)
+    elif r == 4:
+        if p < 84:
+            return None
+        return (m4_1 + m4_2(n-10,n-10), 29)
+    elif r == 5:
+        if p < 85:
+            return None
+        return (m5_1 + m5_2(n-10,n-10), 29)
+    elif r == 6:
+        if p < 102:
+            return None
+        return (m6_1 + m6_2(n-12,n-12), 29)
+    else:
+        if p < 127:
+            return None
+        return (m7_1 + m7_2(n-15,n-15), 29)
+
+cfuncs = (universal_reflector_loop,)