diff --git a/maidroid/api.lua b/maidroid/api.lua
index 9bf5d71..da89ac2 100644
--- a/maidroid/api.lua
+++ b/maidroid/api.lua
@@ -81,6 +81,40 @@ function maidroid.maidroid.get_nearest_player(self, range_distance)
 	return player
 end
 
+-- maidroid.maidroid.get_front_node returns a node that exists in front of the maidroid.
+function maidroid.maidroid.get_front_node(self)
+	local direction = self.object:get_look_dir()
+	direction.y = 0
+	direction = vector.normalize(direction)
+
+	if direction.x >= 0.5 then
+		if direction.x > 0 then	direction.x = 1	else direction.x = -1 end
+	else
+		direction.x = 0
+	end
+
+	if direction.z >= 0.5 then
+		if direction.z > 0 then	direction.z = 1	else direction.z = -1 end
+	else
+		direction.z = 0
+	end
+
+	local front = vector.add(vector.round(self.object:getpos()), direction)
+	return minetest.get_node(front)
+end
+
+-- maidroid.maidroid.set_animation sets the maidroid's animation.
+-- this method is wrapper for self.object:set_animation.
+function maidroid.maidroid.set_animation(self, frame)
+	self.object:set_animation(frame, 15, 0)
+end
+
+-- maidroid.maidroid.set_yaw_by_direction sets the maidroid's yaw
+-- by a direction vector.
+function maidroid.maidroid.set_yaw_by_direction(self, direction)
+	self.object:setyaw(math.atan2(direction.z, direction.x) + math.pi / 2)
+end
+
 ---------------------------------------------------------------------
 
 -- maidroid.manufacturing_data represents a table that contains manufacturing data.
@@ -298,6 +332,9 @@ function maidroid.register_maidroid(product_name, def)
 		get_core             = maidroid.maidroid.get_core,
 		get_core_name        = maidroid.maidroid.get_core_name,
 		get_nearest_player   = maidroid.maidroid.get_nearest_player,
+		get_front_node       = maidroid.maidroid.get_front_node,
+		set_animation        = maidroid.maidroid.set_animation,
+		set_yaw_by_direction = maidroid.maidroid.set_yaw_by_direction,
 	})
 
 	-- register a spawner for debugging maidroid mods.
diff --git a/maidroid_core_basic/register.lua b/maidroid_core_basic/register.lua
index ff43d00..21c1a58 100644
--- a/maidroid_core_basic/register.lua
+++ b/maidroid_core_basic/register.lua
@@ -3,16 +3,56 @@
 -- https://github.com/tacigar/maidroid
 ------------------------------------------------------------
 
-local function on_start(self)
+local state = {
+	IDLE      = 0,
+	ACCOMPANY = 1,
+}
 
+local function on_start(self)
+	self.state = state.IDLE
+	self.object:setacceleration{x = 0, y = -10, z = 0}
+	self.object:setvelocity{x = 0, y = 0, z = 0}
 end
 
 local function on_stop(self)
-
+	self.state = nil
+	self.object:setvelocty{x = 0, y = 0, z = 0}
 end
 
 local function on_step(self, dtime)
+	local player = self:get_nearest_player(10)
+	if player == nil then
+		self:set_animation(maidroid.animation_frames.STAND)
+		return
+	end
 
+	local position = self.object:getpos()
+	local player_position = player:getpos()
+	local direction = vector.subtract(player_position, position)
+	local velocity = self.object:getvelocity()
+
+	if vector.length(dir) < 3 then
+		if self.state == state.ACCOMPANY then
+			self:set_animation(maidroid.animation_frames.STAND)
+			self.state = state.idle
+			self.object:setvelocity{x = 0, y = velocity.y, z = 0}
+		end
+	else
+		if self.state == state.IDLE then
+			self:set_animation(maidroid.animation_frames.WALK)
+			self.state = state.ACCOMPANY
+		end
+		self.object:setvelocity{x = direction.x, y = velocity.y, z = direction.z} -- TODO
+	end
+	self:set_yaw_by_direction(direction)
+
+	-- if maidroid is stoped by obstacle, the maidroid must jump.
+	if velocity == 0 and self.state = state.ACCOMPANY then
+		local front_node = self:get_front_node()
+		if front_node.name ~= "air" then
+			self.object:setvelocity{x = direction.x, y = 3, z = direction.z}
+		end
+	end
 end
 
 maidroid.register_core("maidroid_core_basic:core_basic", {