diff --git a/2020/sketch_2020_09_21a/ponto.py b/2020/sketch_2020_09_21a/ponto.py
new file mode 100644
index 00000000..e9458dab
--- /dev/null
+++ b/2020/sketch_2020_09_21a/ponto.py
@@ -0,0 +1,17 @@
+
+
+class Ponto():
+    
+    SIZE = 5
+    
+    def __init__(self, x, y):
+        self.x = x
+        self.y = y
+        self.f = 255
+        
+    def __getitem__(self, i):
+        return (self.x, self.y)[i]
+        
+    def draw(self):
+        fill(self.f)
+        circle(self.x, self.y, Ponto.SIZE)
diff --git a/2020/sketch_2020_09_21a/sketch_2020_09_21a.gif b/2020/sketch_2020_09_21a/sketch_2020_09_21a.gif
new file mode 100644
index 00000000..1bdb289d
Binary files /dev/null and b/2020/sketch_2020_09_21a/sketch_2020_09_21a.gif differ
diff --git a/2020/sketch_2020_09_21a/sketch_2020_09_21a.pyde b/2020/sketch_2020_09_21a/sketch_2020_09_21a.pyde
new file mode 100644
index 00000000..34a4a05f
--- /dev/null
+++ b/2020/sketch_2020_09_21a/sketch_2020_09_21a.pyde
@@ -0,0 +1,45 @@
+from ponto import Ponto
+
+pontos = []
+dragg = []
+
+def setup():
+    size(400, 400)
+    for _ in range(20):
+        pontos.append(Ponto(random(width),
+                            random(height)))
+        
+def draw():
+    background(200)
+    
+    if len(dragg) == 2:    
+        line(dragg[0][0], dragg[0][1], mouseX, mouseY)
+        
+    for p in pontos:
+        if len(dragg) == 2:
+            if area(p, dragg[0], dragg[1]) > 0:
+                p.f = color(255, 0, 0)
+            else:
+                p.f = color(0, 0, 255)
+        else:
+            p.f = 255
+        p.draw()
+        
+                        
+def mousePressed():
+    dragg[:] = [(mouseX, mouseY)]
+    
+def mouseDragged():
+    if len(dragg) == 1:
+        dragg.append((mouseX, mouseY))
+    else:
+        dragg[1] = (mouseX, mouseY)
+
+def area(p0, p1, p2):
+    a = (p1[0] * (p2[1] - p0[1]) +
+         p2[0] * (p0[1] - p1[1]) +
+         p0[0] * (p1[1] - p2[1]))
+    return a
+
+def mouseReleased():
+    dragg[:] = []
diff --git a/README.md b/README.md
index 294330bf..e58e9ff1 100644
--- a/README.md
+++ b/README.md
@@ -26,6 +26,12 @@ Some of the tools I have used:
 
 ---
 
+![sketch_2020_09_21a](2020/sketch_2020_09_21a/sketch_2020_09_21a.gif)
+
+[sketch_2020_09_21a](https://github.com/villares/sketch-a-day/tree/master/2020/sketch_2020_09_21a) [[Py.Processing](https://villares.github.io/como-instalar-o-processing-modo-python/index-EN)]
+
+---
+
 ![sketch_2020_09_20polycubes_p5py](2020/sketch_2020_09_20polycubes_p5py/sketch_2020_09_20polycubes_p5py.gif)
 
 [sketch_2020_09_20polycubes_p5py](https://github.com/villares/sketch-a-day/tree/master/2020/sketch_2020_09_20polycubes_p5py) [[p5py](https://github.com/p5py/p5)]]