diff --git a/entity/Piece.py b/entity/Piece.py
index 8a59055..05b8ca9 100644
--- a/entity/Piece.py
+++ b/entity/Piece.py
@@ -10,27 +10,28 @@ class Piece: # TODO game objects base class / interface?
         
     def __init__(self, shape, position, color):
         self.color = color
-        self.center, self.points = self.__get_points(shape, position)
+        self.points = self.__get_points(shape, position)
+        self.center = self.__get_center(shape, position)
 
     def __get_points(self, shape, position):
         tile_size = ConfigurationManager.configuration["engine"]["tile-size"]
 
-        center = ()
         points = []
-        for square in shape:
+        for square in shape[:-1]:
             sub_points = []
             for vertex in square:
-                # convert shape vertex into game surface point
                 point = [vertex[0] * tile_size + position[0], vertex[1] * tile_size + position[1]]
                 sub_points.append(point)
-
-                # store center of gravity
-                if len(vertex) > 2 and vertex[2]:
-                    center = point
-
             points.append(sub_points)
 
-        return center, points
+        return points
+
+    def __get_center(self, shape, position):
+        tile_size = ConfigurationManager.configuration["engine"]["tile-size"]
+        center = shape[-1]
+
+        # cast to int and avoid exception from pygame
+        return [int(center[0] * tile_size + position[0]), int(center[1] * tile_size + position[1])]
 
     def draw(self, surface):
         tile_size = ConfigurationManager.configuration["engine"]["tile-size"]
@@ -44,6 +45,9 @@ class Piece: # TODO game objects base class / interface?
             pygame.draw.polygon(surface, border_color, sub_points, max(tile_size // 6, 1))
 
     def move(self, vector):
+        self.center[0] += vector[0]
+        self.center[1] += vector[1]
+
         for sub_points in self.points:
             for point in sub_points:
                 point[0] += vector[0]
@@ -59,9 +63,9 @@ class Piece: # TODO game objects base class / interface?
                 h = point[0] - self.center[0]
                 k = point[1] - self.center[1]
 
-                point[0] = k + self.center[0]
-                point[1] = (h * -1) + self.center[1]
+                point[0] = (k * -1) + self.center[0]
+                point[1] = h + self.center[1]
 
     # shape attributes
-    I_SHAPE = (((0, 0), (1, 0), (1, 1), (0, 1)), ((1, 0), (2, 0), (2, 1), (1, 1)), ((2, 0, True), (3, 0), (3, 1), (2, 1)), ((3, 0), (4, 0), (4, 1), (3, 1)))
-    O_PIECE = ()
+    I_SHAPE = (((0, 0), (1, 0), (1, 1), (0, 1)), ((1, 0), (2, 0), (2, 1), (1, 1)), ((2, 0), (3, 0), (3, 1), (2, 1)), ((3, 0), (4, 0), (4, 1), (3, 1)), (2, 0))
+    J_SHAPE = (((0, 0), (1, 0), (1, 1), (0, 1)), ((1, 0), (2, 0), (2, 1), (1, 1)), ((2, 0), (3, 0), (3, 1), (2, 1)), ((2, 1), (3, 1), (3, 2), (2, 2)), (1.5, 0.5))
diff --git a/main.py b/main.py
index 91ae2cd..e39468f 100644
--- a/main.py
+++ b/main.py
@@ -1,3 +1,8 @@
+'''
+    Tetris 101:
+    https://strategywiki.org/wiki/Tetris/Getting_Started
+'''
+
 import pygame
 
 from entity.Piece import Piece
@@ -25,6 +30,7 @@ def main():
     win_title = ConfigurationManager.configuration["window"]["title"]
     fps = ConfigurationManager.configuration["engine"]["fps"]
     base_one_color = ConfigurationManager.configuration["color"]["base-1"]
+    base_two_color = ConfigurationManager.configuration["color"]["base-2"]
     tile_size = ConfigurationManager.configuration["engine"]["tile-size"]
 
     screen = pygame.display.set_mode((win_width, win_height))
@@ -35,6 +41,7 @@ def main():
     pygame.display.set_icon(loaded_icon)
 
     i_piece = Piece(Piece.I_SHAPE, (100, 100), base_one_color)
+    j_piece = Piece(Piece.J_SHAPE, (250, 100), base_two_color)
 
     is_running = True
     while is_running:
@@ -46,16 +53,21 @@ def main():
             if event.type == pygame.KEYDOWN:
                 if event.key == pygame.K_SPACE:
                     i_piece.rotate()
+                    j_piece.rotate()
                 if event.key == pygame.K_LEFT:
                     i_piece.move((-tile_size, 0))
+                    j_piece.move((-tile_size, 0))
                 if event.key == pygame.K_RIGHT:
                     i_piece.move((tile_size, 0))
+                    j_piece.move((tile_size, 0))
                 if event.key == pygame.K_UP:
                     i_piece.move((0, -tile_size))
+                    j_piece.move((0, -tile_size))
                 if event.key == pygame.K_DOWN:
                     i_piece.move((0, tile_size))
+                    j_piece.move((0, tile_size))
         
-        draw(screen, [i_piece])
+        draw(screen, [i_piece, j_piece])
 
     pygame.quit()