diff --git a/hello-ga/hello-ga.factor b/hello-ga/hello-ga.factor
index 268b6ab..508d66b 100644
--- a/hello-ga/hello-ga.factor
+++ b/hello-ga/hello-ga.factor
@@ -2,7 +2,7 @@
 ! See http://factorcode.org/license.txt for BSD license
 
 USING: fry kernel make math math.order math.ranges random
-sequences ;
+sequences combinators.random ;
 
 IN: hello-ga
 
@@ -22,9 +22,6 @@ CONSTANT: POPULATION 400
 
 CONSTANT: CHILDREN-PROBABILITY 0.9
 
-: children? ( -- ? )
-    0.0 1.0 uniform-random-float CHILDREN-PROBABILITY < ;
-
 : head/tail ( seq1 seq2 n -- head1 tail2 )
     [ head ] [ tail ] bi-curry bi* ;
 
@@ -37,9 +34,6 @@ CONSTANT: CHILDREN-PROBABILITY 0.9
 
 CONSTANT: MUTATION-PROBABILITY 0.2
 
-: mutation? ( -- ? )
-    0.0 1.0 uniform-random-float MUTATION-PROBABILITY < ;
-
 : mutate ( chromosome -- chromosome' )
     dup length random over [ -5 5 [a,b] random + ] change-nth ;
 
@@ -53,8 +47,8 @@ CONSTANT: MUTATION-PROBABILITY 0.2
     dup [ tournament ] bi@ ;
 
 : (1generation) ( seq -- child1 child2 )
-    parents children? [ children ] when
-    mutation? [ [ mutate ] bi@ ] when ;
+    parents CHILDREN-PROBABILITY [ children ] whenp
+    MUTATION-PROBABILITY [ [ mutate ] bi@ ] whenp ;
 
 : 1generation ( seq -- seq' )
     [ length 2 / ] keep