diff --git a/Makefile.rv b/Makefile.rv
index 266116f7..fdb2900d 100644
--- a/Makefile.rv
+++ b/Makefile.rv
@@ -191,6 +191,9 @@ treeoflife-white: hyper
 collatz: hyper
 	${CMD} -canvas h -dftcolor 206020FF -ggamma 2 -collatz .3,.5,-.4,.4
 
+collatz-bird: hyper
+	${CMD} -canvas h -dftcolor R -ggamma 2 -geo 435h -collatz3 txy .3 fd .25 tyz pi/2 / txy -.4 fd .2 tyz pi/2 -PM 0 -rvshape 3 -I Flash 100 -I Speed 100
+
 fullnet: hyper
 	${CMD} -dftcolor 808080FF -ggamma 2 -back FFFFFF -net
 
diff --git a/commandline.cpp b/commandline.cpp
index c94672f4..6085d16a 100644
--- a/commandline.cpp
+++ b/commandline.cpp
@@ -60,9 +60,10 @@ namespace arg {
   int pos;
 
   void lshift() { pos++; }
+  void unshift() { pos--; }
 
   void shift() {
-    lshift(); if(pos > isize(argument)) { printf("Missing parameter\n"); exit(1); }
+    lshift(); if(pos >= isize(argument)) { printf("Missing parameter\n"); exit(1); }
     }
   
   bool nomore() { return pos >= isize(argument); }
@@ -74,7 +75,7 @@ namespace arg {
   ld argf() { return parseld(args()); }
   bool argis(const string& s) { if(args()[0] == '-' && args()[1] == '-') return args().substr(1) == s; return args() == s; }
   
-  void init(int argc, char **argv) { for(int i=0; i<argc; i++) argument.push_back(argv[i]); shift(); }
+  void init(int argc, char **argv) { for(int i=0; i<argc; i++) argument.push_back(argv[i]); lshift(); }
  
   void phaseerror(int x) {
     printf("Command line error: cannot read command '%s' from phase %d in phase %d\n", args().c_str(), x, curphase);
diff --git a/hyper.h b/hyper.h
index abf57a78..0343e686 100644
--- a/hyper.h
+++ b/hyper.h
@@ -2284,6 +2284,7 @@ namespace arg {
 #if CAP_COMMANDLINE
   
   void lshift();
+  void unshift();
 
   void shift();
 
diff --git a/rogueviz.cpp b/rogueviz.cpp
index aa50fb6c..a8ea023f 100644
--- a/rogueviz.cpp
+++ b/rogueviz.cpp
@@ -1720,15 +1720,16 @@ int readArgs() {
     using namespace collatz; 
     s2 = p2 = s3 = p3 = 0;
     start();
-    shift();
     transmatrix *T = &T2;
     while(true) {
+      lshift();
       if(arg::nomore()) break;
-      else if(argis("fd")) { shift(); *T = *T * xpush(argf()); shift(); }
-      else if(argcs()[0] == 't') { int x = dimid(argcs()[1]); int y = dimid(argcs()[2]); shift(); *T = *T * hr::cspin(x, y, argf()); shift(); }
-      else if(argis("/")) { shift(); if(T == &T2) T = &T3; else break; }
+      else if(argis("fd")) { shift(); *T = *T * xpush(argf()); }
+      else if(argcs()[0] == 't') { int x = dimid(argcs()[1]); int y = dimid(argcs()[2]); shift(); *T = *T * hr::cspin(x, y, argf()); }
+      else if(argis("/")) { if(T == &T2) T = &T3; else break; }
       else break;
       }
+    unshift();
     }
 
   else if(argis("-spiral")) {