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diff --git a/2020/sketch_2020_02_11a/forms.py b/2020/sketch_2020_02_11a/forms.py
new file mode 100644
index 00000000..a28d9fc9
--- /dev/null
+++ b/2020/sketch_2020_02_11a/forms.py
@@ -0,0 +1,165 @@
+def b_poly_arc_augmented(op_list, or_list=None, check_intersection=False):
+    if not op_list: return
+    if or_list == None:
+        r2_list = [0] * len(op_list)
+    else:
+        r2_list = or_list[:]
+    assert len(op_list) == len(r2_list), \
+        "Number of points and radii not the same"
+    # remove overlapping adjacent points
+    p_list, r_list = [], []
+    for i1, p1 in enumerate(op_list):
+        i2 = (i1 - 1)
+        p2, r2, r1 = op_list[i2], r2_list[i2], r2_list[i1]
+        if dist(p1[0], p1[1], p2[0], p2[1]) > 1:  # or p1 != p2:
+            p_list.append(p1)
+            r_list.append(r1)
+        else:
+            r2_list[i2] = min(r1, r2)
+    # invert radius
+    for i1, p1 in enumerate(p_list):
+        i0 = (i1 - 1)
+        p0 = p_list[i0]
+        i2 = (i1 + 1) % len(p_list)
+        p2 = p_list[i2]
+        a = area(p0, p1, p2) / 1000.
+        if or_list == None:
+            r_list[i1] = a
+        else:
+            # if abs(a) < 1:
+            #     r_list[i1] = r_list[i1] * abs(a)
+            if a <= 0:
+                r_list[i1] = -r_list[i1]
+    # reduce radius that won't fit
+    for i1, p1 in enumerate(p_list):
+        i2 = (i1 + 1) % len(p_list)
+        p2, r2, r1 = p_list[i2], r_list[i2], r_list[i1]
+        r_list[i1], r_list[i2] = reduce_radius(p1, p2, r1, r2)
+    # calculate the tangents
+    a_list = []
+    for i1, p1 in enumerate(p_list):
+        i2 = (i1 + 1) % len(p_list)
+        p2, r2, r1 = p_list[i2], r_list[i2], r_list[i1]
+        a = circ_circ_tangent(p1, p2, r1, r2)
+        a_list.append(a)
+    # draw
+    beginShape()
+    for i1, ia in enumerate(a_list):
+        i2 = (i1 + 1) % len(a_list)
+        p1, p2, r1, r2 = p_list[i1], p_list[i2], r_list[i1], r_list[i2]
+        a1, p11, p12 = ia
+        a2, p21, p22 = a_list[i2]
+        circle(p1[0], p1[1], 10, 10)
+        if a1 != None and a2 != None:
+            start = a1 if a1 < a2 else a1 - TWO_PI
+            if r2 < 0:
+                a2 = a2 - TWO_PI
+            b_arc(p2[0], p2[1], r2 * 2, r2 * 2, start, a2, mode=2)
+        else:
+            # when the the segment is smaller than the diference between
+            # radius, circ_circ_tangent won't renturn the angle
+            # ellipse(p2[0], p2[1], r2 * 2, r2 * 2) # debug
+            if a1:
+                vertex(p12[0], p12[1])
+            if a2:
+                vertex(p21[0], p21[1])
+    endShape(CLOSE)
+
+def reduce_radius(p1, p2, r1, r2):
+    d = dist(p1[0], p1[1], p2[0], p2[1])
+    ri = abs(r1 - r2)
+    if d - ri <= 0:
+        if abs(r1) > abs(r2):
+            r1 = map(d, ri + 1, 0, r1, r2)
+        else:
+            r2 = map(d, ri + 1, 0, r2, r1)
+    return(r1, r2)
+
+def circ_circ_tangent(p1, p2, r1, r2):
+    d = dist(p1[0], p1[1], p2[0], p2[1])
+    ri = r1 - r2
+    line_angle = atan2(p1[0] - p2[0], p2[1] - p1[1])
+    if d - abs(ri) >= 0:
+        theta = asin(ri / float(d))
+        x1 = -cos(line_angle + theta) * r1
+        y1 = -sin(line_angle + theta) * r1
+        x2 = -cos(line_angle + theta) * r2
+        y2 = -sin(line_angle + theta) * r2
+        return (line_angle + theta,
+                (p1[0] - x1, p1[1] - y1),
+                (p2[0] - x2, p2[1] - y2))
+    else:
+        return (None,
+                (p1[0], p1[1]),
+                (p2[0], p2[1]))
+
+def b_arc(cx, cy, w, h, start_angle, end_angle, mode=0):
+    """
+    A bezier approximation of an arc
+    using the same signature as the original Processing arc()
+    mode: 0 "normal" arc, using beginShape() and endShape()
+              1 "middle" used in recursive call of smaller arcs
+              2 "naked" like normal, but without beginShape() and endShape()
+                 for use inside a larger PShape
+    """
+    theta = end_angle - start_angle
+    # Compute raw Bezier coordinates.
+    if mode != 1 or abs(theta) < HALF_PI:
+        x0 = cos(theta / 2.0)
+        y0 = sin(theta / 2.0)
+        x3 = x0
+        y3 = 0 - y0
+        x1 = (4.0 - x0) / 3.0
+        if y0 != 0:
+            y1 = ((1.0 - x0) * (3.0 - x0)) / (3.0 * y0)  # y0 != 0...
+        else:
+            y1 = 0
+        x2 = x1
+        y2 = 0 - y1
+        # Compute rotationally-offset Bezier coordinates, using:
+        # x' = cos(angle) * x - sin(angle) * y
+        # y' = sin(angle) * x + cos(angle) * y
+        bezAng = start_angle + theta / 2.0
+        cBezAng = cos(bezAng)
+        sBezAng = sin(bezAng)
+        rx0 = cBezAng * x0 - sBezAng * y0
+        ry0 = sBezAng * x0 + cBezAng * y0
+        rx1 = cBezAng * x1 - sBezAng * y1
+        ry1 = sBezAng * x1 + cBezAng * y1
+        rx2 = cBezAng * x2 - sBezAng * y2
+        ry2 = sBezAng * x2 + cBezAng * y2
+        rx3 = cBezAng * x3 - sBezAng * y3
+        ry3 = sBezAng * x3 + cBezAng * y3
+        # Compute scaled and translated Bezier coordinates.
+        rx, ry = w / 2.0, h / 2.0
+        px0 = cx + rx * rx0
+        py0 = cy + ry * ry0
+        px1 = cx + rx * rx1
+        py1 = cy + ry * ry1
+        px2 = cx + rx * rx2
+        py2 = cy + ry * ry2
+        px3 = cx + rx * rx3
+        py3 = cy + ry * ry3
+        # Debug points... comment this out!
+        # stroke(0)
+        # ellipse(px3, py3, 15, 15)
+        # ellipse(px0, py0, 5, 5)
+    # Drawing
+    if mode == 0:  # 'normal' arc (not 'middle' nor 'naked')
+        beginShape()
+    if mode != 1:  # if not 'middle'
+        vertex(px3, py3)
+    if abs(theta) < HALF_PI:
+        bezierVertex(px2, py2, px1, py1, px0, py0)
+    else:
+        # to avoid distortion, break into 2 smaller arcs
+        b_arc(cx, cy, w, h, start_angle, end_angle - theta / 2.0, mode=1)
+        b_arc(cx, cy, w, h, start_angle + theta / 2.0, end_angle, mode=1)
+    if mode == 0:  # end of a 'normal' arc
+        endShape()
+
+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
diff --git a/2020/sketch_2020_02_11a/line_geometry.py b/2020/sketch_2020_02_11a/line_geometry.py
new file mode 100644
index 00000000..ef5087aa
--- /dev/null
+++ b/2020/sketch_2020_02_11a/line_geometry.py
@@ -0,0 +1,164 @@
+
+def intersecting(poly_points):
+    ed = edges(poly_points)
+    intersect = False
+    for p1, p2 in ed[::-1]:
+        for p3, p4 in ed[2::]:
+            # test only non consecutive edges
+            if (p1 != p3) and (p2 != p3) and (p1 != p4):
+                if line_instersect(Line(p1, p2), Line(p3, p4)):
+                    intersect = True
+                    break
+    return intersect
+     
+def is_inside(x, y, poly_points):   
+    min_, max_ = min_max(poly_points)
+    if x < min_.x or y < min_.y or x > max_.x or y > max_.y:
+        return False
+    
+    a = PVector(x, min_.y)
+    b = PVector(x, max_.y)
+    v_lines = inter_lines(Line(a, b), poly_points)
+    if not v_lines:
+        return False
+        
+    a = PVector(min_.x, y)
+    b = PVector(max_.x, y)
+    h_lines = inter_lines(Line(a, b), poly_points)
+    if not h_lines:
+        return False
+                
+    for v in v_lines:
+        for h in h_lines:
+            if line_instersect(v, h):
+                return True   
+                         
+    return False
+
+
+def inter_lines(L, poly_points):
+    inter_points = []
+    for p1, p2 in edges(poly_points):
+        inter = line_instersect(Line(p1, p2), L)
+        if inter:
+            inter_points.append(inter)
+    if  not inter_points:
+        return []
+    inter_lines = []
+    if len(inter_points) > 1:
+        inter_points.sort()
+        pairs = zip(inter_points[::2], inter_points[1::2])
+        for p1, p2 in pairs:
+            if p2:
+                inter_lines.append(Line(PVector(p1.x, p1.y),
+                                        PVector(p2.x, p2.y))) 
+    return inter_lines
+
+        
+class Line():
+    """ I should change this to a named tuple... """
+    def __init__(self, p1, p2):
+        self.p1 = PVector(*p1)
+        self.p2 = PVector(*p2) 
+    
+    def __getitem__(self, i):
+        return (self.p1, self.p2)[i]
+        
+    def plot(self):
+        line(self.p1.x, self.p1.y, self.p2.x, self.p2.y)
+    
+    def lerp(self, other, t):
+        p1 = PVector.lerp(self.p1, other.p1, t)
+        p2 = PVector.lerp(self.p2, other.p2, t)
+        return Line(p1, p2)
+    
+def line_instersect(line_a, line_b):     
+    """
+    code adapted from Bernardo Fontes 
+    https://github.com/berinhard/sketches/
+    """
+    x1, y1 = line_a.p1.x, line_a.p1.y
+    x2, y2 = line_a.p2.x, line_a.p2.y
+    x3, y3 = line_b.p1.x, line_b.p1.y
+    x4, y4 = line_b.p2.x, line_b.p2.y
+    try:
+        uA = ((x4-x3)*(y1-y3) - (y4-y3)*(x1-x3)) / ((y4-y3)*(x2-x1) - (x4-x3)*(y2-y1));
+        uB = ((x2-x1)*(y1-y3) - (y2-y1)*(x1-x3)) / ((y4-y3)*(x2-x1) - (x4-x3)*(y2-y1));
+    except ZeroDivisionError:
+        return
+    if not(0 <= uA <= 1 and 0 <= uB <= 1):
+        return
+    x = line_a.p1.x + uA * (line_a.p2.x - line_a.p1.x)
+    y = line_a.p1.y + uA * (line_a.p2.y - line_a.p1.y)
+        
+    return PVector(x, y)
+    # """
+    # code adapted from 
+    # https://stackoverflow.com/questions/27745972/test-if-polylines-intersects-using-python
+    # """
+    # xdiff = (line1[0][0] - line1[1][0], line2[0][0] - line2[1][0])
+    # ydiff = (line1[0][1] - line1[1][1], line2[0][1] - line2[1][1])
+
+    # def det(a, b):
+    #     return a[0] * b[1] - a[1] * b[0]
+
+    # div = det(xdiff, ydiff)
+    # if div == 0:
+    #    return None
+
+    # d = (det(*line1), det(*line2))
+    # x = det(d, xdiff) / div
+    # y = det(d, ydiff) / div
+    # return x, y
+    # return PVector(x, y)
+
+
+def edges(poly_points):
+    return pairwise(poly_points) + [(poly_points[-1], poly_points[0])]   
+
+def pairwise(iterable):
+    import itertools
+    "s -> (s0,s1), (s1,s2), (s2, s3), ..."
+    a, b = itertools.tee(iterable)
+    next(b, None)
+    return zip(a, b) 
+
+def edges_as_sets(poly_points):
+    edge_set_pairs = set()
+    for edge in edges(poly_points):
+       s = frozenset(edge)
+       edge_set_pairs.add(s)
+    return frozenset(edge_set_pairs)
+
+
+def min_max(points):
+        points = iter(points)
+        try:
+            p = points.next()
+            min_x, min_y = max_x, max_y = p.x, p.y
+        except StopIteration:
+            raise ValueError, "min_max requires at least one point"
+        for p in points:
+            if p.x < min_x:
+                min_x = p.x
+            elif p.x > max_x:
+                max_x = p.x
+            if p.y < min_y:
+                min_y = p.y
+            elif p.y > max_y:
+                max_y = p.y
+        return (PVector(min_x, min_y),
+                PVector(max_x, max_y))
+        
+def par_hatch(points, divisions, *sides):
+        vectors = [PVector(p.x, p.y) for p in points]
+        lines = []
+        if not sides: sides = [0]
+        for s in sides:
+            a, b = vectors[-1 + s], vectors[+0 + s]
+            d, c = vectors[-2 + s], vectors[-3 + s]
+            for i in range(1, divisions):
+                s0 = PVector.lerp(a, b, i/float(divisions))
+                s1 = PVector.lerp(d, c, i/float(divisions))
+                lines.append(Line(s0, s1)) 
+        return lines
diff --git a/2020/sketch_2020_02_11a/sketch_2020_02_11a.png b/2020/sketch_2020_02_11a/sketch_2020_02_11a.png
new file mode 100644
index 00000000..b8131652
Binary files /dev/null and b/2020/sketch_2020_02_11a/sketch_2020_02_11a.png differ
diff --git a/2020/sketch_2020_02_11a/sketch_2020_02_11a.pyde b/2020/sketch_2020_02_11a/sketch_2020_02_11a.pyde
new file mode 100644
index 00000000..6a32b698
--- /dev/null
+++ b/2020/sketch_2020_02_11a/sketch_2020_02_11a.pyde
@@ -0,0 +1,91 @@
+# Alexandre B A Villares - https://abav.lugaralgum.com/sketch-a-day
+
+from random import choice, sample, shuffle
+from itertools import product, permutations, combinations
+from forms import b_poly_arc_augmented
+from line_geometry import *
+
+NUM_POINTS = 6
+BORDER = 100
+SIZE = 100
+RDS = 50
+
+def setup():
+    size(500, 500)
+    global ensambles
+    ensambles = create_ensambles(create_points(), 30)
+    
+def create_ensambles(polys, r=1):
+    ens = []
+    for poly in polys:
+        for i in range(64):
+            rads = []
+            rad_opts = num_to_base(i, 2, 6)
+            for c in rad_opts:
+                if c == "0":
+                    rads.append(-1 * r)
+                else:
+                    rads.append(1 * r)
+            shuffle(rads)
+            print(rads)
+            ens.append((poly, rads))
+    return ens  
+
+def create_points():
+    """ non intersecting poly """
+    grid = list(product(range(BORDER, width - BORDER + 1, SIZE),
+                        range(BORDER, height - BORDER + 1, SIZE)))
+    points = sample(grid, 6)
+    total = list(combinations(grid, 6))
+    polys = list(permutations(points, NUM_POINTS))
+    tested = set()
+    for poly in polys[:]:
+        edges = edges_as_sets(poly)
+        if edges not in tested and edges:
+            tested.add(edges) 
+        else:
+            polys.remove(poly)
+    print("inicial: {}".format(len(polys)))
+    ni_polys = []
+    for poly in polys:
+        if not intersecting(poly):
+            ni_polys.append(poly) 
+    print("sem auto-cruzar: {}".format(len(ni_polys)))
+    return list(ni_polys)
+
+def draw():
+    background(200)
+    # b_poly_arc_augmented(ens, [30] * 6)
+    background(200)
+    scale(1/16.)
+    e = 0
+    total = len(ensambles)
+    for j in range(16):
+        for i in range(16):
+            pushMatrix()
+            translate(width * i, height * j)  
+            if e < total:
+                noFill()
+                strokeWeight(16)
+                b_poly_arc_augmented(ensambles[e][0], ensambles[e][1])
+            popMatrix()
+            e += 1
+
+def keyPressed():
+    if key == "p" or key == 'P':
+        saveFrame("####.png")
+    if key == ' ':
+        ensambles[:] = create_ensambles(create_points(), 30)
+
+
+def num_to_base(num, base, pad=0):
+    BS = ""
+    for i in range(base):
+        BS += str(i)
+    result = ""
+    while num:
+        result += BS[num % base]
+        num //= base
+    while len(result) < pad:
+        result = result + "0"
+    return result[::-1]