diff --git a/history/003_trap/src/main/java/com/github/drinkjava2/frog/objects/Material.java b/history/003_trap/src/main/java/com/github/drinkjava2/frog/objects/Material.java
new file mode 100644
index 0000000..ca66cc7
--- /dev/null
+++ b/history/003_trap/src/main/java/com/github/drinkjava2/frog/objects/Material.java
@@ -0,0 +1,40 @@
+/* Copyright 2018-2020 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.objects;
+
+import java.awt.Color;
+
+/**
+ * Object means some thing in Env
+ * 
+ * @author Yong Zhu
+ * @since 1.0
+ */
+public class Material {
+	public static final byte VISIBLE = 10; // if>=10 will visible to frog
+	public static final byte KILLFROG = 20; // if>=20 will kill frog
+
+	public static final byte NO = 0;
+	public static final byte SEESAW_BASE = 1; // 1~9 is invisible to frog
+
+	public static final byte FOOD = VISIBLE + 1;
+	public static final byte SEESAW = VISIBLE + 2; // if <0 will not cause frog die
+
+	public static final byte BRICK = KILLFROG + 1;
+	public static final byte TRAP = KILLFROG + 2;
+
+	public static Color color(byte material) {
+		if (material == TRAP)
+			return Color.LIGHT_GRAY;
+		else
+			return Color.BLACK;
+	}
+}