diff --git a/2019/sketch_190502a/sketch_190502a.pyde b/2019/sketch_190502a/sketch_190502a.pyde
index 8b17d55e..1caeb518 100644
--- a/2019/sketch_190502a/sketch_190502a.pyde
+++ b/2019/sketch_190502a/sketch_190502a.pyde
@@ -135,7 +135,7 @@ def keyPressed():
         outer_radius -= 5
     if keyCode == LEFT:
         inner_radius += 5
-    if keyCode == base_rGHT:
+    if keyCode == RIGHT:
         inner_radius -= 5
     if key == "+":
         sides += 1
diff --git a/2019/sketch_190503a/sketch_190503a.png b/2019/sketch_190503a/sketch_190503a.png
new file mode 100644
index 00000000..4073abe5
Binary files /dev/null and b/2019/sketch_190503a/sketch_190503a.png differ
diff --git a/2019/sketch_190503a/sketch_190503a.pyde b/2019/sketch_190503a/sketch_190503a.pyde
new file mode 100644
index 00000000..cb48c49c
--- /dev/null
+++ b/2019/sketch_190503a/sketch_190503a.pyde
@@ -0,0 +1,145 @@
+"""
+Alexandre B A Villares - https://abav.lugaralgum.com/sketch-a-day
+
+- Unfolding prism
+"""
+
+# add_library('GifAnimation')
+# from gif_exporter import gif_export
+
+CUT_STROKE = color(255, 0, 0)
+FOLD_STROKE = color(0, 0, 255)
+
+p_height, inner_radius = 100, 50
+sides = 5
+
+def setup():
+    size(400, 600, P3D)
+    hint(ENABLE_DEPTH_TEST)
+    hint(ENABLE_DEPTH_SORT)
+
+def draw():
+    background(240)
+    pushMatrix()
+    translate(width / 2, height / 4 + 50)
+    rotateX(radians(45))
+    rotateZ(radians(frameCount / 3.))
+    fill(255, 200)
+    stroke(0)
+    strokeWeight(2)
+    # draw 3D piramid and get points
+    points = prism_3D(sides, p_height, inner_radius)
+    popMatrix()
+    # draw unfolded 2D
+    translate(width / 2, height *  3 / 4 - 50)
+    prism_2D(points)
+
+def prism_3D(np, h, base_r):
+    # calculando os points
+    points = []
+    for i in range(np):
+        ang = radians(i * 360. / np)
+        x = sin(ang) * base_r
+        y = cos(ang) * base_r
+        points.append((x, y))
+    # edges da base
+    base_points = points[::]
+    o_base_points = base_points[1:] + [base_points[0]]
+    base_edges = zip(base_points, o_base_points)
+    for edge in base_edges:
+            (p1x, p1y), (p2x, p2y) = edge
+            beginShape()
+            vertex(p1x, p1y, 0)
+            vertex(p1x, p1y, h)
+            vertex(p2x, p2y, h)
+            vertex(p2x, p2y, 0)
+            endShape(CLOSE)
+    # always draws base
+    beginShape()
+    for pt in base_points:
+        vertex(pt[0], pt[1], h)
+    endShape(CLOSE)
+    # return points for 2D!
+    return points
+
+def prism_2D(points):
+    noFill()
+    # base fold lines
+    stroke(FOLD_STROKE)
+    beginShape()
+    for pt in points:
+        vertex(*pt)
+    endShape(CLOSE)
+    # lateral edges
+    o_points = points[1:] + [points[0]]
+    edges = zip(points, o_points)
+    for i, edge in enumerate(edges):
+        p1, p2 = edge
+        stroke(CUT_STROKE)
+        # abas de cola
+        glue_tab(p2, p1, 10, )
+        # FOLD_STROKE
+        stroke(FOLD_STROKE)
+        line(p2[0], p2[1], p1[0], p1[1])
+        
+def glue_tab(p1, p2, tab_w, cut_ang=QUARTER_PI / 3):
+    """
+    draws a trapezoidal or triangular glue tab along edge defined by p1 and p2,
+    with width tab_w and cut angle a
+    """
+    al = atan2(p1[0] - p2[0], p1[1] - p2[1])
+    a1 = al + cut_ang + PI
+    a2 = al - cut_ang
+    # calculate cut_len to get the base_rght tab width
+    cut_len = tab_w / sin(cut_ang)
+    f1 = (p1[0] + cut_len * sin(a1),
+          p1[1] + cut_len * cos(a1))
+    f2 = (p2[0] + cut_len * sin(a2),
+          p2[1] + cut_len * cos(a2))
+    edge_len = dist(p1[0], p1[1], p2[0], p2[1])
+
+    if edge_len > 2 * cut_len * cos(cut_ang):    # 'normal' trapezoidal tab
+        beginShape()
+        vertex(*p1)    # vertex(p1[0], p1[1])
+        vertex(*f1)
+        vertex(*f2)
+        vertex(*p2)
+        endShape()
+    else:    # short triangular tab
+        fm = ((f1[0] + f2[0]) / 2, (f1[1] + f2[1]) / 2)
+        beginShape()
+        vertex(*p1)
+        vertex(*fm)    # middle way of f1 and f2
+        vertex(*p2)
+        endShape()
+
+def keyPressed():
+    global inner_radius, p_height, sides
+    if keyCode == UP:
+        p_height += 5
+    if keyCode == DOWN:
+        p_height -= 5
+    if keyCode == LEFT:
+        inner_radius += 5
+    if keyCode == RIGHT:
+        inner_radius -= 5
+    if key == "+":
+        sides += 1
+    if key == "-" and sides > 3:
+        sides -= 1
+
+    # if key == "g":
+    #     gif_export(GifMaker, filename=SKETCH_NAME)
+
+def settings():
+    from os import path
+    global SKETCH_NAME
+    SKETCH_NAME = path.basename(sketchPath())
+    OUTPUT = ".gif"
+    println(
+        """
+![{0}]({2}/{0}/{0}{1})
+
+[{0}](https://github.com/villares/sketch-a-day/tree/master/{2}/{0}) [[Py.Processing](https://villares.github.io/como-instalar-o-processing-modo-python/index-EN)]
+""".format(SKETCH_NAME, OUTPUT, year())
+    )
diff --git a/README.md b/README.md
index 216b52e7..0cd856c9 100644
--- a/README.md
+++ b/README.md
@@ -22,6 +22,13 @@ Get updates from my sort-of-weekly newsletter: [[sketch-mail](https://villares.o
 
 ## 2019
 
+
+---
+
+![sketch_190503a](2019/sketch_190503a/sketch_190503a.png)
+
+[sketch_190503a](https://github.com/villares/sketch-a-day/tree/master/2019/sketch_190503a) [[Py.Processing](https://villares.github.io/como-instalar-o-processing-modo-python/index-EN)]
+
 ---
 
 ![sketch_190502a](2019/sketch_190502a/sketch_190502a.gif)