diff --git a/s236/s236.pyde b/s236/s236.pyde
index 1ef4c230..3f0f9116 100644
--- a/s236/s236.pyde
+++ b/s236/s236.pyde
@@ -1,5 +1,5 @@
 # Alexandre B A Villares - https://abav.lugaralgum.com/sketch-a-day
-SKETCH_NAME = "s236" #20180821
+SKETCH_NAME = "s236" #20180822
 
 # made my own randint so no need of this: # from random import randint
 from gif_export_wrapper import gif_export
diff --git a/s237/gif_export_wrapper.py b/s237/gif_export_wrapper.py
new file mode 100644
index 00000000..29f73319
--- /dev/null
+++ b/s237/gif_export_wrapper.py
@@ -0,0 +1,49 @@
+"""
+Alexandre B A Villares http://abav.lugaralgum.com - GPL v3 
+
+Version 180811
+A helper for the Processing gifAnimation library (https://github.com/jordanorelli)
+ported to Processing 3 by 01010101 (https://github.com/01010101)
+Download the library from https://github.com/01010101/GifAnimation/archive/master.zip
+This helper was inspired by an example by Art Simon https://github.com/APCSPrinciples/AnimatedGIF/
+
+Put  at the start of your sketch:
+   add_library('gifAnimation')
+   from gif_exporter import gif_export
+and at the end of draw():
+    gif_export(GifMaker)
+"""
+
+def gif_export(GifMaker,             # gets a reference to the library
+               filename="exported",  # .gif will be added
+               repeat=0,             # 0 makes it an "endless" animation
+               quality=128,          # quality range 0 - 255
+               delay=400,            # this is quick
+               frames=0,
+               finish=False):            # 0 will stop on keyPressed or frameCount >= 100000
+    global gifExporter
+    try:
+        gifExporter
+    except NameError:
+        gifExporter = GifMaker(this, filename + ".gif")
+        gifExporter.setRepeat(repeat)
+        gifExporter.setQuality(quality)
+        gifExporter.setDelay(delay)
+        gif_export._frame = frameCount
+        print("gif start")
+
+    gifExporter.addFrame()
+    if finish:
+        gifExporter.finish()
+        print("gif saved")
+        noLoop()
+        return False
+    if  frames != 0 and frameCount - gif_export._frame >= frames:
+        gifExporter.finish()
+        #background(255)
+        print("gif saved")
+        del(gifExporter)
+        noLoop()
+        return False
+    else:
+        return True
diff --git a/s237/my_box.py b/s237/my_box.py
new file mode 100644
index 00000000..aae0b652
--- /dev/null
+++ b/s237/my_box.py
@@ -0,0 +1,48 @@
+def my_box(side):
+    front = ((-1, +1, -1),
+             (-1, +1, +1),
+             (+1, +1, +1),
+             (+1, +1, -1),
+             )
+    back = ((-1, -1, -1),
+            (-1, -1, +1),
+            (+1, -1, +1),
+            (+1, -1, -1),
+            )
+    left = ((-1, -1, -1),
+            (-1, -1, +1),
+            (-1, +1, +1),
+            (-1, +1, -1),
+            )
+    right = ((+1, -1, -1),
+             (+1, -1, +1),
+             (+1, +1, +1),
+             (+1, +1, -1),
+             )
+    down = ((-1, -1, -1),
+            (+1, -1, -1),
+            (+1, +1, -1),
+            (-1, +1, -1),
+            )
+    top = ((-1, -1, +1),
+           (+1, -1, +1),
+           (+1, +1, +1),
+           (-1, +1, +1),
+           )
+
+    faces = ((top, color(255)),
+             (down, color(0)),
+             (right, color(150)),
+             (left, color(150)),
+             (back, color(75)),
+             (front, color(75)),
+             )
+
+    for pts, shade in faces:
+        hs = side / 2  # half side
+        #fill(shade)
+        beginShape()
+        for pt in pts:
+            x, y, z = pt
+            vertex(x * hs, y * hs, z * hs)
+        endShape(CLOSE)
diff --git a/s237/s237.pyde b/s237/s237.pyde
new file mode 100644
index 00000000..2bb5e912
--- /dev/null
+++ b/s237/s237.pyde
@@ -0,0 +1,225 @@
+# Alexandre B A Villares - https://abav.lugaralgum.com/sketch-a-day
+SKETCH_NAME = "s237" #20180823
+
+# made my own randint so no need of this: # from random import randint
+from gif_export_wrapper import gif_export
+from my_box import my_box
+add_library('gifAnimation')
+add_library('peasycam')
+add_library('dxf')
+add_library('OBJExport')
+
+GRID_SIZE = 32
+OUTPUT = ".gif"
+# Cutting-plane position (press + & - to change)
+cut_plane = GRID_SIZE
+export = False
+
+def setup():
+    print_text_for_readme(SKETCH_NAME, OUTPUT)
+    size(700, 700, P3D)
+    colorMode(HSB)
+    # optional PeasyCam setup to allow orbiting with a mouse drag
+    cam = PeasyCam(this, 100)
+    cam.setMinimumDistance(1000)
+    cam.setMaximumDistance(1000)
+    # sets border and grid spacing
+    Node.border = 50
+    Node.spacing = (width - Node.border * 2) / GRID_SIZE
+    # Node.nodes is a list of nodes in a 3D grid
+    for x in range(GRID_SIZE):
+        for y in range(GRID_SIZE):
+            for z in range(GRID_SIZE):
+                new_node = Node(x, y, z)
+                Node.nodes.append(new_node)
+                Node.grid[x, y, z] = new_node
+    # crear objects
+    create_rods()
+    #create_tubes()
+
+def draw():
+    # lights()
+    background(200)
+    if export:
+        beginRaw("nervoussystem.obj.OBJExport", "filename.obj")
+
+    for node in Node.nodes:
+        if node.iz < cut_plane:
+            node.plot()
+
+    if export:
+        endRaw()
+        global export
+        export = False
+
+
+   
+
+def keyPressed():
+    """ press P to save an image """
+    if key in ['p', 'P']:
+        saveFrame("####" + SKETCH_NAME + OUTPUT)
+    if key == " ":
+        for node in Node.nodes:
+            node.cor = None
+        create_rods()
+        create_tubes()
+    if key == "g":
+        gif_export(GifMaker, delay=2000, filename=SKETCH_NAME)
+    if key == "f":
+        gif_export(GifMaker, finish=True)
+    # cut plane adjust
+    global cut_plane, export
+    if key == "-":
+        cut_plane -= 1
+        print(cut_plane)
+    if key in ['+', '=']:
+        cut_plane += 1
+        print(cut_plane)
+    if key == 'e':
+        export = True
+
+
+def big_box(px, py, pz, w, h=None, d=None, c=255):
+    h = h if h else w
+    d = d if d else w
+    for z in range(pz, pz + d):
+        for y in range(py, py + h):
+            for x in range(px, px + w):
+                if (0 <= x < GRID_SIZE and
+                        0 <= y < GRID_SIZE and
+                        0 <= z < GRID_SIZE):
+                    Node.grid[(x, y, z)].cor = c
+
+def big_ugly(px, py, pz, w, h=None, d=None, c=255):
+    h = h if h else w
+    d = d if d else w
+    for z in range(pz, pz + d):
+        for y in range(py, py + h):
+            for x in range(px, px + w):
+                if (0 <= x < GRID_SIZE and
+                        0 <= y < GRID_SIZE and
+                        0 <= z < GRID_SIZE):
+                        orient1 =  x % 2 and y % 2
+                        orient2 = x % 2 and z % 2
+                        orient3 = y % 2 and z % 2
+                        if orient1 or orient2 or orient3:
+                        Node.grid[(x, y, z)].cor = c
+                else:
+                    Node.grid[(x, y, z)].cor = None
+                
+
+
+def create_tubes():
+    # sets the objects, list of tuples -> hollowed boxes
+    seed = int(random(1000)) #seed = 205
+    println("seed: {}".format(seed))
+    randomSeed(seed)
+    m = GRID_SIZE - 1
+    tube_list = []
+    num_tubes = 10
+    border = 1
+    for i in range(num_tubes):
+        # random size in range 3 to GRID_SIZE - borders
+        w = randint(3, m - border * 2)
+        h = randint(3, m - border * 2)
+        d = randint(3, m - border * 2)
+        # random position
+        x = randint(border, m - w - border)
+        y = randint(border, m - h - border)
+        z = randint(border, m - d - border)
+        box_tuple = (x, y, z, w, h, d)
+        print(box_tuple)
+        tube_list.append(box_tuple)
+    # solid boxes 
+    for i in range(num_tubes):
+        x, y, z, w, h, d = tube_list[i]
+        big_box(x, y, z, w, h, d,
+                color(64 + (i % 3) * 32, 200, 200))
+    # erase inside boxes, making tubes
+    for i in range(num_tubes):
+        x, y, z, w, h, d = tube_list[i]
+        side = (i % 3) + 1
+        if side == 1:
+            h -= 2
+            w -= 2
+            z -= 1
+        elif side == 2:
+            d -= 2
+            h -= 2
+            x -= 1
+        else:
+            w -= 2
+            d -= 2
+            y -= 1
+        big_box(x + 1, y + 1, z + 1, w, h, d,
+                # use color(0) below, instead of None to debug
+                # color(0))
+                None)
+
+def create_rods():
+    # sets the objects, list of tuples -> hollowed boxes
+    seed = int(random(1000))  # seed = 205
+    println("seed: {}".format(seed))
+    randomSeed(seed)
+    m = GRID_SIZE - 1
+    box_list = []
+    num_boxes = 10
+    border = 1
+    for i in range(num_boxes):
+        # random size in range 3 to GRID_SIZE - borders
+        w = randint(3, m - border * 2)
+        h = randint(3, m - border * 2)
+        d = randint(3, m - border * 2)
+        # random position
+        x = randint(border, m - w - border)
+        y = randint(border, m - h - border)
+        z = randint(border, m - d - border)
+        box_tuple = (x, y, z, w, h, d)
+        # print(box_tuple)
+        box_list.append(box_tuple)
+    # solid boxes
+    for i in range(num_boxes):
+        x, y, z, w, h, d = box_list[i]
+        big_ugly(x, y, z, w, h, d, color(128 + (i % 3) * 32, 200, 200))
+        
+class Node():
+    nodes = []
+    grid = dict()
+
+    def __init__(self, x, y, z):
+        self.ix = x
+        self.iy = y
+        self.iz = z
+        self.x = Node.border + Node.spacing / 2 + x * Node.spacing - width / 2
+        self.y = Node.border + Node.spacing / 2 + y * Node.spacing - width / 2
+        self.z = Node.border + Node.spacing / 2 + z * Node.spacing - width / 2
+        self.size_ = 1
+        self.cor = None
+
+    def plot(self):
+        """ draws box """
+        if self.cor:
+            #stroke(0, 200)
+            stroke(0)
+            fill(self.cor)
+            with pushMatrix():
+                translate(self.x, self.y, self.z)
+                my_box(Node.spacing * self.size_)
+
+def randint(a, b=None):
+    if not b:
+        b = a
+        a = 0
+    return int(random(a, b + 1))
+
+
+def print_text_for_readme(name, output):
+    """ prints text in the console to add to project README.md """
+    println("""
+![{0}]({0}/{0}{2})
+
+{1}: [code](https://github.com/villares/sketch-a-day/tree/master/{0}) [[Py.Processing](https://villares.github.io/como-instalar-o-processing-modo-python/index-EN)]
+
+""".format(name, name[1:], output)
+    )