diff --git a/2019/sketch_190818a/sketch_190818a.png b/2019/sketch_190818a/sketch_190818a.png
new file mode 100644
index 00000000..056f8e6c
Binary files /dev/null and b/2019/sketch_190818a/sketch_190818a.png differ
diff --git a/2019/sketch_190818a/sketch_190818a.pyde b/2019/sketch_190818a/sketch_190818a.pyde
new file mode 100644
index 00000000..1a8238e0
--- /dev/null
+++ b/2019/sketch_190818a/sketch_190818a.pyde
@@ -0,0 +1,41 @@
+def setup():
+    size(500, 500)
+    rectMode(CENTER)
+    translate(width / 2, height / 2)
+    # grid(10, 10, 45, elem_1234)
+    grid(10, 10, 45, elem_1234, rule_1234)
+
+def grid(cols, rows, spacing, element, rule=lambda *args: None):
+    wid, hei = cols * spacing, rows * spacing
+    for i in range(cols):
+        x = spacing / 2. + i * spacing - wid / 2.
+        for j in range(rows):
+            y = spacing / 2. + j * spacing - hei / 2.
+            element(x, y, rule(i, j, cols, rows, spacing))
+
+def rule_1234(i, j, cols, rows, spacing):
+    """ border and chess """
+    w, h = cols - 1, rows - 1
+    if i == 0 or i == w or j == 0 or j == h:
+        c = color(255)
+    else:
+        c = color(0)
+    if (i + j) % 3 == 0:
+        rot = 0
+    else:
+        rot = QUARTER_PI
+    siz = spacing / (1.02 + (i + j) % 2)
+    return c, rot, siz
+
+def elem_1234(x, y, args):
+    if args != None:
+        c, rot, siz = args
+    else:
+        c, rot, siz = 0, 0, 40
+    noStroke()
+    fill(c)
+    pushMatrix()
+    translate(x, y)
+    rotate(rot)
+    rect(0, 0, siz, siz)
+    popMatrix()
diff --git a/README.md b/README.md
index 54881b3b..ec014628 100644
--- a/README.md
+++ b/README.md
@@ -20,6 +20,12 @@ You may also support my artistic work, open teaching resources and research with
 
 ---
 
+![sketch_1900818a](2019/sketch_190818a/sketch_190818a.png)
+
+[sketch_190818a](https://github.com/villares/sketch-a-day/tree/master/2019/sketch_190818a) [[Py.Processing](https://villares.github.io/como-instalar-o-processing-modo-python/index-EN)]
+
+---
+
 ![sketch_1900817a](2019/sketch_190817a/sketch_190817a.png)
 
 [sketch_190817a](https://github.com/villares/sketch-a-day/tree/master/2019/sketch_190817a) [[Py.Processing](https://villares.github.io/como-instalar-o-processing-modo-python/index-EN)]