diff --git a/history/003a_legs/src/main/java/com/github/drinkjava2/frog/brain/organ/BFootDrop.java b/history/003a_legs/src/main/java/com/github/drinkjava2/frog/brain/organ/BFootDrop.java
new file mode 100644
index 0000000..bf85bce
--- /dev/null
+++ b/history/003a_legs/src/main/java/com/github/drinkjava2/frog/brain/organ/BFootDrop.java
@@ -0,0 +1,33 @@
+/*
+ * Copyright 2018 the original author or authors. 
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at http://www.apache.org/licenses/LICENSE-2.0 Unless required by
+ * applicable law or agreed to in writing, software distributed under the
+ * License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS
+ * OF ANY KIND, either express or implied. See the License for the specific
+ * language governing permissions and limitations under the License.
+ */
+package com.github.drinkjava2.frog.brain.organ;
+
+import com.github.drinkjava2.frog.Frog;
+import com.github.drinkjava2.frog.brain.Organ;
+
+/**
+ * Move down frog 1 unit if outputs of nerve cells active in this zone
+ */
+public class BFootDrop extends Organ {
+	private static final long serialVersionUID = 1L;
+
+	@Override
+	public void active(Frog f) {
+		if (f.bFootStatus == "DOWN")
+			return;
+		if (activedByCells(f)) {
+			actived = true;
+			f.bFootStatus = "DOWN";
+		} else
+			actived = false;
+	}
+
+}