diff --git a/src/experimental/_impl/_lsystem2_impl.scad b/src/experimental/_impl/_lsystem2_impl.scad
index 7d98295f..903c4473 100644
--- a/src/experimental/_impl/_lsystem2_impl.scad
+++ b/src/experimental/_impl/_lsystem2_impl.scad
@@ -6,17 +6,17 @@ function _join(strs) =
     let(leng = len(strs))
     [for(i = 0, s = strs[0]; i < leng; i = i + 1, s = str(s, strs[i])) s][leng - 1];
 
-function _produce1(base, rule) = _join([
+function _derive1(base, rule) = _join([
     for(c = base) 
     let(v = assoc_lookup(rule, c))
     is_undef(v) ? c : v
 ]);
 
-function _produce(base, rule, n, i = 0) =
-    i == n ? base : _produce(_produce1(base, rule), rule, n, i + 1);
+function _derive(base, rule, n, i = 0) =
+    i == n ? base : _derive(_derive1(base, rule), rule, n, i + 1);
     
-function produce(rule, n) =
-    _produce(assoc_lookup(rule, "S"), rule, n);
+function derive(rule, n) =
+    _derive(assoc_lookup(rule, "S"), rule, n);
 
 function cmd(symbol, args) =
     symbol == "F" ? ["forward", args[0]] :
diff --git a/src/experimental/lsystem2.scad b/src/experimental/lsystem2.scad
index bee7077a..17946e8b 100644
--- a/src/experimental/lsystem2.scad
+++ b/src/experimental/lsystem2.scad
@@ -1,16 +1,21 @@
 use <experimental/_impl/_lsystem2_impl.scad>;
 use <turtle/turtle2d.scad>;
 
-function lsystem2(rule, n, angle, leng = 1, heading = 0, start_pt = [0, 0]) =
+function lsystem2(rule, n, angle, leng = 1, heading = 0, start = [0, 0], forward_chars = "F") =
     let(
-        produced = produce(rule, n),
+        derived = derive(rule, n),
+        replaced = _join([
+            for(c = derived)
+            let(idx = search(c, forward_chars))
+            idx == [] ? c : "F"
+        ]),
         cmds = [
-            for(s = produced) 
+            for(s = replaced) 
             let(c = cmd(s, [leng, angle]))
             if(c != []) c
         ]
     )
     _lines(
-        turtle2d("create", start_pt[0], start_pt[0], heading), 
+        turtle2d("create", start[0], start[0], heading), 
         cmds
     );
\ No newline at end of file