--- a/flowsnake.js	Sat Nov 09 23:47:14 2013 +0900
+++ b/flowsnake.js	Sat Nov 09 23:47:54 2013 +0900
@@ -87,6 +87,10 @@
     },
 
     step: function(visible) {
+        if (this.pointer >= this.rule.length) {
+            return false;
+        }
+
         var redraw = false;
 
         switch (this.rule[this.pointer]) {
@@ -103,9 +107,7 @@
                 break;
         }
 
-        if (this.pointer < this.rule.length) {
-            this.pointer++;
-        }
+        this.pointer++;
 
         if (visible) {
             if (redraw) {
@@ -114,6 +116,8 @@
                 this.step(visible);
             }
         }
+
+        return true;
     },
 
     draw: function() {

--- a/index.html	Sat Nov 09 23:47:14 2013 +0900
+++ b/index.html	Sat Nov 09 23:47:54 2013 +0900
@@ -20,8 +20,10 @@
 
         $('pre').css({'left': '50%', 'margin-left': - $('pre').width() / 2});
 
-        window.setInterval(function() {
-          flowsnake.step(true);
+        var interval = window.setInterval(function() {
+          if (!flowsnake.step(true)) {
+            window.clearInterval(interval);
+          }
         }, 50);
       });
     </script>