Rewrite of eop/combinations intro

eop/combinations.py

@@ -83,8 +83,149 @@ class Female(Male):
         "color" : MAROON_B,
     }
 
+class PascalsTraingle(VGroup):
+    CONFIG = {
+        "n_rows" : 9,
+        "distance" : 0.8,
+        "max_width_to_distance_ratio" : 0.7,
+        "angle" : 0.2*np.pi,
+    }
+    def __init__(self, **kwargs):
+        VGroup.__init__(self, **kwargs)
+
+        distance = self.distance
+        angle = self.angle
+        max_width = self.max_width_to_distance_ratio * distance
+        t_down = rotate_vector(distance*DOWN, -angle)
+        t_right = 2*distance*np.sin(angle)*RIGHT
+
+        for n in range(self.n_rows):
+            row = VGroup()
+            for k in range(n+1):
+                num = TexMobject(str(choose(n, k)))
+                num.shift(n*t_down + k*t_right)
+                row.add(num)
+            self.add(row)
+        self.center()
+
 ######################
 
+
+class ExperienceProblemSolver(PiCreatureScene):
+    def construct(self):
+        self.add_equation()
+        self.jenny_solves()
+        self.no_genius()
+        self.think_about_patterns()
+
+    def add_equation(self):
+        equation = TexMobject(
+            "\\frac{x^3 + y^3}{(x+y)^2} + \\frac{3xy}{x+y}"
+        )
+        equation.to_edge(UP)
+
+        self.play(Write(equation))
+        self.dither()
+
+        self.equation = equation
+
+    def jenny_solves(self):
+        randy, jenny = self.randy, self.jenny
+        jenny_words = TextMobject("It's just $x+y$")
+        randy_words = TextMobject("...wait...")
+        randy_words.next_to(randy.get_corner(UP+RIGHT), RIGHT)
+
+        self.pi_creature_says(
+            jenny, jenny_words, 
+            target_mode = "hooray",
+            bubble_kwargs = {"height" : 2, "width" : 3}
+        )
+        self.dither()
+        self.play(
+            randy.change, "confused", self.equation,
+            Write(randy_words)
+        )
+        self.play(randy.look_at, self.equation.get_left())
+        self.play(randy.look_at, jenny.eyes)
+        self.play(jenny.change, "happy")
+        self.play(randy.change, "tired")
+        self.dither()
+        self.play(*map(FadeOut, [
+            jenny.bubble, jenny_words, randy_words
+        ]))
+
+    def no_genius(self):
+        randy, jenny = self.randy, self.jenny
+
+        lightbulb = Lightbulb()
+        lightbulb.next_to(jenny, UP)
+        cross = Cross(lightbulb)
+        cross.set_stroke(RED, 8)
+
+        self.play(LaggedStart(ShowCreation, lightbulb))
+        self.play(
+            ShowCreation(cross),
+            jenny.change, "sassy", cross,
+            randy.change, "happy"
+        )
+        self.dither(2)
+
+        self.to_fade = VGroup(lightbulb, cross)
+
+    def think_about_patterns(self):
+        randy, jenny = self.randy, self.jenny
+        rows = PascalsTraingle(
+            n_rows = 6,
+            distance = 0.6,
+        )
+        rows.scale(0.8)
+        for row in rows:
+            for num in row:
+                n = float(num.get_tex_string())
+                num.highlight(interpolate_color(
+                    BLUE, YELLOW, n/10.0
+                ))
+
+        self.pi_creature_thinks(
+            jenny, "",
+            bubble_kwargs = {"width" : 5, "height" : 4.2},
+            added_anims = [
+                FadeOut(self.to_fade),
+                FadeOut(self.equation),
+                randy.change, "plain"
+            ]
+        )
+        rows.move_to(
+            jenny.bubble.get_bubble_center() + \
+            MED_SMALL_BUFF*(UP+LEFT)
+        )
+        self.play(FadeIn(rows[0]))
+        for last_row, curr_row in zip(rows, rows[1:]):
+            self.play(*[
+                Transform(
+                    last_row.copy(), VGroup(*mobs),
+                    remover = True
+                )
+                for mobs in curr_row[1:], curr_row[:-1]
+            ])
+            self.add(curr_row)
+        self.dither(3)
+
+
+
+
+    ############
+
+    def create_pi_creatures(self):
+        randy = Randolph()
+        randy.to_edge(DOWN)
+        randy.shift(4*LEFT)
+        jenny = PiCreature(color = BLUE_C).flip()
+        jenny.to_edge(DOWN)
+        jenny.shift(4*RIGHT)
+        self.randy, self.jenny = randy, jenny
+        return randy, jenny
+
 class Introduction(Scene):
     CONFIG = {
         "start_n" : 4,
@@ -1275,7 +1416,7 @@ class BuildUpFromStart(Scene):
             for stack in stacks
         ])
 
-class PascalsTriangle(Scene):
+class IntroducePascalsTriangle(Scene):
     CONFIG = {
         "max_n" : 9,
     }
@@ -1288,24 +1429,7 @@ class PascalsTriangle(Scene):
         self.cap_off_triangle()
 
     def show_triangle(self):
-        distance = 0.8
-        max_width = 0.7*distance
-        angle = 0.2*np.pi
-        t_down = rotate_vector(distance*DOWN, -angle)
-        t_right = 2*distance*np.sin(angle)*RIGHT
-
-        rows = VGroup()
-        for n in range(self.max_n + 1):
-            row = VGroup()
-            for k in range(n+1):
-                num = TexMobject(str(choose(n, k)))
-                # if num.get_width() > max_width:
-                #     num.scale_to_fit_width(max_width)
-                num.shift(n*t_down + k*t_right)
-                row.add(num)
-            rows.add(row)
-        rows.to_edge(UP)
-
+        rows = PascalsTraingle(n_rows = self.max_n+1)
         self.play(FadeIn(rows[1]))
         for last_row, curr_row in zip(rows[1:], rows[2:]):
             self.play(*[
@@ -1716,7 +1840,6 @@ class ChooseThreeFromFive(Scene):
         
     def show_four_choose_two_in_binary(self):
         pass
-        
 
 
 

topics/objects.py

@@ -17,6 +17,9 @@ class Lightbulb(SVGMobject):
         "file_name" : "lightbulb",
         "height" : 1,
         "stroke_color" : YELLOW,
+        "stroke_width" : 3,
+        "fill_color" : YELLOW,
+        "fill_opacity" : 0,
     }
 
 class BitcoinLogo(SVGMobject):