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diff --git a/2020/sketch_2020_03_31a/sketch_2020_03_31a.pyde b/2020/sketch_2020_03_31a/sketch_2020_03_31a.pyde
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+# Other L-System
+
+iterations = 8
+base_len = 3500
+angle_deg = 45
+axiom = 'LR'
+sentence = axiom
+rules = {
+    'L': '-R[LFL]',
+    'R': '+L[RFL]',
+}
+
+def setup():
+    size(700, 700)
+    global xo, yo
+    xo, yo = width / 2, height / 2 - 20
+    strokeWeight(0.5)
+    noFill()
+    generate(iterations)
+
+def draw():
+    background(0)
+    translate(xo, yo)
+    plot(radians(angle_deg))
+    resetMatrix()
+    # debug
+    # rectMode(CORNERS)
+    # rect(min_x, min_y, max_x, max_y)
+    rectMode(CORNER)
+    fill(0, 200); noStroke()
+    rect(0, height - 80, width, 80)
+    fill(255)
+    t = "rules = {} axiom: '{}'\niterations:{} angle:{} stroke-len:{} sentence len: {}"
+    t = t.format(rules, axiom, iterations, angle_deg, int(stroke_len), len(sentence))
+    textSize(20)
+    text(t, 10, height - 50)
+
+def generate(n):
+    global stroke_len, sentence
+    for _ in range(n):
+        # stroke_len *= 0.5
+        next_sentence = ''
+        for c in sentence:
+            next_sentence += rules.get(c, c)
+        sentence = next_sentence
+    stroke_len = base_len * 2. / sqrt(len(sentence) + iterations + 10) 
+        
+def plot(angle):
+    record_limits(reset=True)        
+    for c in sentence:
+        if c == 'F':
+            stroke(255)
+            line(0, 0, 0, -stroke_len) # draw white line
+            translate(0, -stroke_len) # move
+        elif c == 'L':
+            stroke(255, 0, 0)
+            noFill()
+            line(0, 0, -stroke_len / 3, 0) # red does not move!
+        elif c == 'R':
+            stroke(0, 0, 255)
+            line(0, 0, stroke_len / 3, 0) # blue does not move! 
+        elif c == '+':
+            rotate(angle)
+        elif c == '-':
+            rotate(-angle)
+        elif c == '[':
+            pushMatrix()
+        elif c == ']':
+            popMatrix()
+        record_limits()        
+            
+def record_limits(reset=None):
+    global max_x, max_y, min_x, min_y
+    if reset is None:
+        x = screenX(0, 0)
+        y = screenY(0, 0)
+        # circle(0, 0, 15)
+        max_x = max(x, max_x)
+        min_x = min(x, min_x)
+        max_y = max(y, max_y)
+        min_y = min(y, min_y)
+    else:
+        max_x = min_x = screenX(0, 0)
+        max_y = min_y = screenY(0, 0)
+
+
+def keyPressed():
+    global angle_deg, xo, yo, stroke_len, iterations, sentence
+    if key == '-':
+        angle_deg -= 1.
+    if str(key) in "=+":
+        angle_deg += 1
+    if key == 's':
+        saveFrame('angle{}-{}.png'.format(angle_deg, iterations))
+    if key == '.':
+        iterations += 1
+        sentence = axiom
+        generate(iterations)
+    if key == ',':
+        iterations -= 1
+        sentence = axiom
+        generate(iterations)
+    if key == 'a':
+        stroke_len *= 1.1
+    if key == 'z':
+        stroke_len /= 1.1
+    if keyCode == LEFT:
+        xo -= 50
+    if keyCode == RIGHT:
+        xo += 50
+    if keyCode == UP:
+        yo -= 50
+    if keyCode == DOWN:
+        yo += 50
+    if key == ' ':
+        # print(max_x, max_y, min_x, min_y)
+        dx = max_x - min_x
+        dy = max_y - min_y
+        if dx > width - 25 or dy > height - 25:
+            print(dx, dy)
+            stroke_len /= 1.1
+        else:
+            if max_x > width:
+                xo -= 25
+            elif min_x < 0:
+                xo += 25
+            if max_y > height:
+                yo -= 25
+            elif min_y < 0:
+                yo += 25
+            
+        
+def settings():
+    """ print markdown to add at the sketc-a-day page"""
+    from os import path
+    global SKETCH_NAME
+    SKETCH_NAME = path.basename(sketchPath())
+    OUTPUT = ".png"
+    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())
+    )