diff --git a/2021/sketch_2021_01_23a/cell.py b/2021/sketch_2021_01_23a/cell.py
new file mode 100644
index 00000000..354d3535
--- /dev/null
+++ b/2021/sketch_2021_01_23a/cell.py
@@ -0,0 +1,71 @@
+def hex_color(s):
+    """
+    This function allows you to create color from a string with hex notation in Python mode.
+    
+    On "standard" Processing (Java) we can use hexadecimal color notation #AABBCC
+    On Python mode one can use this notation between quotes, as a string in fill(),
+    stroke() and background(), but, unfortunately, not with color().
+    """
+    if s.startswith('#'):
+        s = s[1:]
+    return color(int(s[:2], 16), int(s[2:4], 16), int(s[4:6], 16))
+
+class Cell():
+    colors = (hex_color('#264653'),
+              hex_color('#2a9d8f'), 
+              hex_color('#9c46a'), 
+              hex_color('#f4a261'),
+              hex_color('#e76f51'))
+    
+    def __init__(self, index, cell_size):
+        self.index = index
+        self.state = False
+        self.s = cell_size
+        self.mouse_down = False
+        i, j = index[0], index[1]
+        self.pos = PVector(self.s/2 + i * self.s,
+                           self.s/2 + j * self.s)
+        self.ngbs = []
+        NL = ((-1, -1), (+0, -1), (+1, -1),
+              (-1, +0),           (+1, +0),
+              (-1, +1), (+0, +1), (+1, +1))
+        for ni, nj in NL:
+            self.ngbs.append(
+                    Cell.grid.get((i-ni, j-nj), None))   
+        
+    def play(self):
+        # mouse_on = dist(self.pos.x, self.pos.y,
+        #                 mouseX, mouseY) < self.s/2
+        hs = self.s / 2
+        px, py = self.pos.x, self.pos.y
+        mouse_on = (px - hs < mouseX < px + hs and
+                    py - hs < mouseY < py + hs)
+        if mouse_on and mousePressed:
+            self.mouse_down = True
+        if self.mouse_down and not mousePressed:
+            self.state = (self.state + 1) % len(Cell.colors)
+            self.mouse_down = False
+
+        # if mouse_on and mousePressed:
+        #     self.mouse_down = True
+        # elif self.mouse_down and mouse_on:
+        #     self.state = not self.state
+        #     self.mouse_down = False
+        # else:
+        #     self.mouse_down = False
+        noStroke()
+        fill(Cell.colors[self.state])   
+        rect(self.pos.x, self.pos.y,
+             self.s,
+             self.s
+             )
+        if mouse_on:
+             with pushStyle():
+                stroke(255)
+                noFill()
+                rect(self.pos.x, self.pos.y,
+                self.s-1,
+                self.s-1
+                )
+ 
+        
diff --git a/2021/sketch_2021_01_23a/sketch_2021_01_23a.png b/2021/sketch_2021_01_23a/sketch_2021_01_23a.png
new file mode 100644
index 00000000..81575bca
Binary files /dev/null and b/2021/sketch_2021_01_23a/sketch_2021_01_23a.png differ
diff --git a/2021/sketch_2021_01_23a/sketch_2021_01_23a.pyde b/2021/sketch_2021_01_23a/sketch_2021_01_23a.pyde
new file mode 100644
index 00000000..bc9c664c
--- /dev/null
+++ b/2021/sketch_2021_01_23a/sketch_2021_01_23a.pyde
@@ -0,0 +1,31 @@
+from cell import Cell
+
+CELL_SIZE = 25
+Cell.grid = dict()
+grid_lines = True
+
+def setup():
+    size(500, 500)
+    rectMode(CENTER)
+    init_grid(width//CELL_SIZE, height//CELL_SIZE)
+
+def init_grid(w, h):
+    for i in range(w):
+        for j in range(h):
+            Cell.grid[(i, j)] = Cell((i,j), CELL_SIZE)    
+            
+def draw():
+    if grid_lines:
+        stroke(0)
+    else:
+        noStroke()
+    for c in Cell.grid.values():
+        c.play()
+        
+        
+        
+        
+        
+        
+        
+        
diff --git a/README.md b/README.md
index 43aacc6e..33f5cc3a 100644
--- a/README.md
+++ b/README.md
@@ -26,6 +26,12 @@ Here are listed some of the tools I have been using:
 
 ---
 
+![sketch_2021_01_23a](2021/sketch_2021_01_23a/sketch_2021_01_23a.png)
+
+[sketch_2021_01_23a](https://github.com/villares/sketch-a-day/tree/master/2021/sketch_2021_01_23a) [[Py.Processing](https://villares.github.io/como-instalar-o-processing-modo-python/index-EN)]
+
+---
+
 ![sketch_2021_01_22b_recursive_grid](2021/sketch_2021_01_22b_recursive_grid/sketch_2021_01_22b_recursive_grid.gif)
 
 [sketch_2021_01_22b_recursive_grid](https://github.com/villares/sketch-a-day/tree/master/2021/sketch_2021_01_22b_recursive_grid) [[Py.Processing](https://villares.github.io/como-instalar-o-processing-modo-python/index-EN)]