diff --git a/Search-based Planning/Search_2D/Anytime_D_star.py b/Search-based Planning/Search_2D/Anytime_D_star.py
new file mode 100644
index 0000000..d58a0e7
--- /dev/null
+++ b/Search-based Planning/Search_2D/Anytime_D_star.py	
@@ -0,0 +1,309 @@
+"""
+Anytime_D_star 2D
+@author: huiming zhou
+"""
+
+import os
+import sys
+import math
+import matplotlib.pyplot as plt
+
+sys.path.append(os.path.dirname(os.path.abspath(__file__)) +
+                "/../../Search-based Planning/")
+
+from Search_2D import plotting
+from Search_2D import env
+
+
+class ADStar:
+    def __init__(self, s_start, s_goal, eps, heuristic_type):
+        self.s_start, self.s_goal = s_start, s_goal
+        self.heuristic_type = heuristic_type
+
+        self.Env = env.Env()  # class Env
+        self.Plot = plotting.Plotting(s_start, s_goal)
+
+        self.u_set = self.Env.motions  # feasible input set
+        self.obs = self.Env.obs  # position of obstacles
+        self.x = self.Env.x_range
+        self.y = self.Env.y_range
+
+        self.g, self.rhs, self.OPEN = {}, {}, {}
+
+        for i in range(1, self.Env.x_range - 1):
+            for j in range(1, self.Env.y_range - 1):
+                self.rhs[(i, j)] = float("inf")
+                self.g[(i, j)] = float("inf")
+
+        self.rhs[self.s_goal] = 0.0
+        self.eps = eps
+        self.OPEN[self.s_goal] = self.Key(self.s_goal)
+        self.CLOSED, self.INCONS = set(), dict()
+
+        self.visited = set()
+        self.count = 0
+        self.count_env_change = 0
+        self.obs_add = set()
+        self.obs_remove = set()
+        self.title = "Anytime D*: Small changes"  # significant changes
+        self.fig = plt.figure()
+
+    def run(self):
+        self.Plot.plot_grid(self.title)
+        self.ComputeOrImprovePath()
+        self.plot_visited()
+        self.plot_path(self.extract_path())
+        self.visited = set()
+
+        while True:
+            if self.eps <= 1.0:
+                break
+            self.eps -= 0.5
+            self.OPEN.update(self.INCONS)
+            for s in self.OPEN:
+                self.OPEN[s] = self.Key(s)
+            self.CLOSED = set()
+            self.ComputeOrImprovePath()
+            self.plot_visited()
+            self.plot_path(self.extract_path())
+            self.visited = set()
+            plt.pause(0.5)
+
+        self.fig.canvas.mpl_connect('button_press_event', self.on_press)
+        plt.show()
+
+    def on_press(self, event):
+        x, y = event.xdata, event.ydata
+        if x < 0 or x > self.x - 1 or y < 0 or y > self.y - 1:
+            print("Please choose right area!")
+        else:
+            self.count_env_change += 1
+            x, y = int(x), int(y)
+            print("Change position: x =", x, ",", "y =", y)
+
+            # for small changes
+            if self.title == "Anytime D*: Small changes":
+                if (x, y) not in self.obs:
+                    self.obs.add((x, y))
+                    plt.plot(x, y, 'sk')
+                    self.g[(x, y)] = float("inf")
+                    self.rhs[(x, y)] = float("inf")
+                else:
+                    self.obs.remove((x, y))
+                    plt.plot(x, y, marker='s', color='white')
+                    self.UpdateState((x, y))
+
+                for sn in self.get_neighbor((x, y)):
+                    self.UpdateState(sn)
+
+                while True:
+                    if len(self.INCONS) == 0:
+                        break
+                    self.OPEN.update(self.INCONS)
+                    for s in self.OPEN:
+                        self.OPEN[s] = self.Key(s)
+                    self.CLOSED = set()
+                    self.ComputeOrImprovePath()
+                    self.plot_visited()
+                    self.plot_path(self.extract_path())
+                    plt.plot(self.title)
+                    self.visited = set()
+
+                    if self.eps <= 1.0:
+                        break
+
+            else:
+                if (x, y) not in self.obs:
+                    self.obs.add((x, y))
+                    self.obs_add.add((x, y))
+                    plt.plot(x, y, 'sk')
+                    if (x, y) in self.obs_remove:
+                        self.obs_remove.remove((x, y))
+                else:
+                    self.obs.remove((x, y))
+                    self.obs_remove.add((x, y))
+                    plt.plot(x, y, marker='s', color='white')
+                    if (x, y) in self.obs_add:
+                        self.obs_add.remove((x, y))
+
+                if self.count_env_change >= 15:
+                    self.count_env_change = 0
+                    self.eps += 2.0
+                    for s in self.obs_add:
+                        self.g[(x, y)] = float("inf")
+                        self.rhs[(x, y)] = float("inf")
+
+                        for sn in self.get_neighbor(s):
+                            self.UpdateState(sn)
+
+                    for s in self.obs_remove:
+                        for sn in self.get_neighbor(s):
+                            self.UpdateState(sn)
+                        self.UpdateState(s)
+
+                    while True:
+                        if self.eps <= 1.0:
+                            break
+                        self.eps -= 0.5
+                        self.OPEN.update(self.INCONS)
+                        for s in self.OPEN:
+                            self.OPEN[s] = self.Key(s)
+                        self.CLOSED = set()
+                        self.ComputeOrImprovePath()
+                        self.plot_visited()
+                        self.plot_path(self.extract_path())
+                        plt.title(self.title)
+                        self.visited = set()
+                        plt.pause(0.5)
+
+            self.fig.canvas.draw_idle()
+
+    def ComputeOrImprovePath(self):
+        while True:
+            s, v = self.TopKey()
+            if v >= self.Key(self.s_start) and \
+                    self.rhs[self.s_start] == self.g[self.s_start]:
+                break
+
+            self.OPEN.pop(s)
+            self.visited.add(s)
+
+            if self.g[s] > self.rhs[s]:
+                self.g[s] = self.rhs[s]
+                self.CLOSED.add(s)
+                for sn in self.get_neighbor(s):
+                    self.UpdateState(sn)
+            else:
+                self.g[s] = float("inf")
+                for sn in self.get_neighbor(s):
+                    self.UpdateState(sn)
+                self.UpdateState(s)
+
+    def UpdateState(self, s):
+        if s != self.s_goal:
+            self.rhs[s] = float("inf")
+            for x in self.get_neighbor(s):
+                self.rhs[s] = min(self.rhs[s], self.g[x] + self.cost(s, x))
+        if s in self.OPEN:
+            self.OPEN.pop(s)
+
+        if self.g[s] != self.rhs[s]:
+            if s not in self.CLOSED:
+                self.OPEN[s] = self.Key(s)
+            else:
+                self.INCONS[s] = 0
+
+    def Key(self, s):
+        if self.g[s] > self.rhs[s]:
+            return [self.rhs[s] + self.eps * self.h(self.s_start, s), self.rhs[s]]
+        else:
+            return [self.g[s] + self.h(self.s_start, s), self.g[s]]
+
+    def TopKey(self):
+        """
+        :return: return the min key and its value.
+        """
+
+        s = min(self.OPEN, key=self.OPEN.get)
+        return s, self.OPEN[s]
+
+    def h(self, s_start, s_goal):
+        heuristic_type = self.heuristic_type  # heuristic type
+
+        if heuristic_type == "manhattan":
+            return abs(s_goal[0] - s_start[0]) + abs(s_goal[1] - s_start[1])
+        else:
+            return math.hypot(s_goal[0] - s_start[0], s_goal[1] - s_start[1])
+
+    def cost(self, s_start, s_goal):
+        """
+        Calculate cost for this motion
+        :param s_start: starting node
+        :param s_goal: end node
+        :return:  cost for this motion
+        :note: cost function could be more complicate!
+        """
+
+        if self.is_collision(s_start, s_goal):
+            return float("inf")
+
+        return math.hypot(s_goal[0] - s_start[0], s_goal[1] - s_start[1])
+
+    def is_collision(self, s_start, s_end):
+        if s_start in self.obs or s_end in self.obs:
+            return True
+
+        if s_start[0] != s_end[0] and s_start[1] != s_end[1]:
+            if s_end[0] - s_start[0] == s_start[1] - s_end[1]:
+                s1 = (min(s_start[0], s_end[0]), min(s_start[1], s_end[1]))
+                s2 = (max(s_start[0], s_end[0]), max(s_start[1], s_end[1]))
+            else:
+                s1 = (min(s_start[0], s_end[0]), max(s_start[1], s_end[1]))
+                s2 = (max(s_start[0], s_end[0]), min(s_start[1], s_end[1]))
+
+            if s1 in self.obs or s2 in self.obs:
+                return True
+
+        return False
+
+    def get_neighbor(self, s):
+        nei_list = set()
+        for u in self.u_set:
+            s_next = tuple([s[i] + u[i] for i in range(2)])
+            if s_next not in self.obs:
+                nei_list.add(s_next)
+
+        return nei_list
+
+    def extract_path(self):
+        """
+        Extract the path based on the PARENT set.
+        :return: The planning path
+        """
+
+        path = [self.s_start]
+        s = self.s_start
+
+        for k in range(100):
+            g_list = {}
+            for x in self.get_neighbor(s):
+                if not self.is_collision(s, x):
+                    g_list[x] = self.g[x]
+            s = min(g_list, key=g_list.get)
+            path.append(s)
+            if s == self.s_goal:
+                break
+
+        return list(path)
+
+    def plot_path(self, path):
+        px = [x[0] for x in path]
+        py = [x[1] for x in path]
+        plt.plot(px, py, linewidth=2)
+        plt.plot(self.s_start[0], self.s_start[1], "bs")
+        plt.plot(self.s_goal[0], self.s_goal[1], "gs")
+
+    def plot_visited(self):
+        self.count += 1
+
+        color = ['gainsboro', 'lightgray', 'silver', 'darkgray',
+                 'bisque', 'navajowhite', 'moccasin', 'wheat',
+                 'powderblue', 'skyblue', 'lightskyblue', 'cornflowerblue']
+
+        if self.count >= len(color) - 1:
+            self.count = 0
+
+        for x in self.visited:
+            plt.plot(x[0], x[1], marker='s', color=color[self.count])
+
+
+def main():
+    s_start = (5, 5)
+    s_goal = (45, 25)
+
+    dstar = ADStar(s_start, s_goal, 2.5, "euclidean")
+    dstar.run()
+
+
+if __name__ == '__main__':
+    main()
diff --git a/Search-based Planning/Search_2D/astar.py b/Search-based Planning/Search_2D/Astar.py
similarity index 100%
rename from Search-based Planning/Search_2D/astar.py
rename to Search-based Planning/Search_2D/Astar.py
diff --git a/Search-based Planning/Search_2D/best_first.py b/Search-based Planning/Search_2D/Best_First.py
similarity index 100%
rename from Search-based Planning/Search_2D/best_first.py
rename to Search-based Planning/Search_2D/Best_First.py
diff --git a/Search-based Planning/Search_2D/bidirectional_a_star.py b/Search-based Planning/Search_2D/Bidirectional_a_star.py
similarity index 100%
rename from Search-based Planning/Search_2D/bidirectional_a_star.py
rename to Search-based Planning/Search_2D/Bidirectional_a_star.py
diff --git a/Search-based Planning/Search_2D/D_star_Lite.py b/Search-based Planning/Search_2D/D_star_Lite.py
index 175920a..ea10baf 100644
--- a/Search-based Planning/Search_2D/D_star_Lite.py	
+++ b/Search-based Planning/Search_2D/D_star_Lite.py	
@@ -89,6 +89,7 @@ class DStar:
                     self.count += 1
                     self.visited = set()
                     self.ComputePath()
+
             self.plot_visited(self.visited)
             self.plot_path(path)
             self.fig.canvas.draw_idle()
diff --git a/Search-based Planning/Search_2D/dijkstra.py b/Search-based Planning/Search_2D/Dijkstra.py
similarity index 100%
rename from Search-based Planning/Search_2D/dijkstra.py
rename to Search-based Planning/Search_2D/Dijkstra.py
diff --git a/Search-based Planning/Search_2D/PotentialField.py b/Search-based Planning/Search_2D/PotentialField.py
index 497a5c0..44d0c85 100644
--- a/Search-based Planning/Search_2D/PotentialField.py	
+++ b/Search-based Planning/Search_2D/PotentialField.py	
@@ -12,7 +12,6 @@ from collections import deque
 sys.path.append(os.path.dirname(os.path.abspath(__file__)) +
                 "/../../Search-based Planning/")
 
-import
 from Search_2D import plotting
 from Search_2D import env
 
diff --git a/Search-based Planning/gif/ADstar_sig.gif b/Search-based Planning/gif/ADstar_sig.gif
new file mode 100644
index 0000000..8f40972
Binary files /dev/null and b/Search-based Planning/gif/ADstar_sig.gif differ
diff --git a/Search-based Planning/gif/ADstar_small.gif b/Search-based Planning/gif/ADstar_small.gif
new file mode 100644
index 0000000..582156c
Binary files /dev/null and b/Search-based Planning/gif/ADstar_small.gif differ