Starting chapter 2 of eola

animation/simple_animations.py

@@ -130,14 +130,23 @@ class Homotopy(Animation):
         """
         Homotopy a function from (x, y, z, t) to (x', y', z')
         """
-        digest_config(self, kwargs, locals())
+        def function_at_time_t(t):
+            return lambda p : homotopy(p[0], p[1], p[2], t)
+        self.function_at_time_t = function_at_time_t
+        digest_config(self, kwargs)
         Animation.__init__(self, mobject, **kwargs)
 
     def update_mobject(self, alpha):
-        self.mobject.points = np.array([
-            self.homotopy((x, y, z, alpha))
-            for x, y, z in self.starting_mobject.points
-        ])
+        pairs = zip(
+            self.mobject.submobject_family(),
+            self.starting_mobject.submobject_family()
+        )
+        for mob, start_mob in pairs:
+            mob.become_partial(start_mob, 0, 1)
+        self.mobject.apply_function(
+            self.function_at_time_t(alpha)
+        )
+
 
 class PhaseFlow(Animation):
     CONFIG = {

animation/transform.py

@@ -8,7 +8,7 @@ from helpers import *
 
 from animation import Animation
 from simple_animations import DelayByOrder
-from mobject import Mobject, Point
+from mobject import Mobject, Point, VMobject
 
 class Transform(Animation):
     CONFIG = {
@@ -100,6 +100,8 @@ class FadeIn(Transform):
     def __init__(self, mobject, **kwargs):
         target = mobject.copy()
         mobject.fade(1)
+        if isinstance(mobject, VMobject):
+            mobject.set_stroke(width = 0)
         Transform.__init__(self, mobject, target, **kwargs)
         # self.mobject.rgbs = self.starting_mobject.rgbs * alpha
         # if self.mobject.points.shape != self.starting_mobject.points.shape:

eola/chapter0.py

@@ -18,7 +18,8 @@ from mobject.svg_mobject import *
 from mobject.tex_mobject import *
 from mobject.vectorized_mobject import *
 
-from eola.utils import *
+from eola.matrix import *
+from eola.two_d_space import *
 
 EXAMPLE_TRANFORM = [[0, 1], [-1, 1]]
 TRANFORMED_VECTOR = [[1], [2]]

eola/chapter1.py

@@ -18,7 +18,9 @@ from mobject.svg_mobject import *
 from mobject.tex_mobject import *
 from mobject.vectorized_mobject import *
 
-from eola.utils import *
+from eola.matrix import *
+from eola.two_d_space import *
+from eola.chapter0 import UpcomingSeriesOfVidoes
 
 import random
 
@@ -326,6 +328,14 @@ class DifferentConceptions(Scene):
         syms.arrange_submobjects(RIGHT)
         syms.center().shift(2*UP)
 
+        statement = TextMobject("We'll ignore him \\\\ for now")
+        statement.highlight(PINK)
+        statement.scale_to_fit_width(arrays.get_width())
+        statement.next_to(arrays, DOWN, buff = 2)
+        arrow_to_mathy = Arrow(statement, mathy, color = PINK, buff = 0)
+        circle = Circle()
+        circle.shift(syms.get_bottom())
+
         VMobject(v_arrow, v_array, v_sym).highlight(v_color)
         VMobject(w_arrow, w_array, w_sym).highlight(w_color)
         VMobject(sum_arrow, sum_array).highlight(sum_color)
@@ -338,6 +348,16 @@ class DifferentConceptions(Scene):
         )
         self.play(Blink(mathy))
         self.add_scaling(arrows, syms, arrays)
+        self.play(Write(statement))
+        self.play(ShowCreation(arrow_to_mathy, submobject_mode = "one_at_a_time"))
+        self.play(ApplyMethod(mathy.change_mode, "sad"))
+        self.dither()
+        self.play(
+            ShowCreation(circle),
+            ApplyMethod(mathy.change_mode, "plain")
+        )
+        self.dither()
+
 
     def add_scaling(self, arrows, syms, arrays):
         s_arrows = VMobject(
@@ -658,8 +678,10 @@ class Write3DVector(Scene):
 class VectorAddition(VectorScene):
     def construct(self):
         self.add_plane()
-        self.define_addition()
-        self.answer_why()
+        vects = self.define_addition()
+        # vects = map(Vector, [[1, 2], [3, -1], [4, 1]])
+        self.ask_why(*vects)
+        self.answer_why(*vects)
 
     def define_addition(self):
         v1 = self.add_vector([1, 2])
@@ -673,9 +695,415 @@ class VectorAddition(VectorScene):
         sum_tex = "\\vec{\\textbf{v}} + \\vec{\\textbf{w}}"
         self.label_vector(v_sum, sum_tex, rotate = True)
         self.dither(3)
+        return v1, v2, v_sum
+
+    def ask_why(self, v1, v2, v_sum):
+        why = TextMobject("Why?")
+        why_not_this = TextMobject("Why not \\\\ this?")
+        new_v2 = v2.copy().shift(-v2.get_start())
+        new_v_sum = v_sum.copy()
+        alt_vect_sum = new_v2.get_end() - v1.get_end()
+        new_v_sum.shift(-new_v_sum.get_start())
+        new_v_sum.rotate(
+            angle_of_vector(alt_vect_sum) - new_v_sum.get_angle()
+        )
+        new_v_sum.scale(np.linalg.norm(alt_vect_sum)/new_v_sum.get_length())
+        new_v_sum.shift(v1.get_end())
+        new_v_sum.submobjects.reverse()#No idea why I have to do this
+        original_v_sum = v_sum.copy()
+
+        why.next_to(v2, RIGHT)
+        why_not_this.next_to(new_v_sum, RIGHT)
+        why_not_this.shift(0.5*UP)
+
+        self.play(Write(why, run_time = 1))
+        self.dither(2)
+        self.play(
+            Transform(v2, new_v2),
+            Transform(v_sum, new_v_sum),            
+            Transform(why, why_not_this)
+        )
+        self.dither(2)
+        self.play(
+            FadeOut(why),
+            Transform(v_sum, original_v_sum)
+        )
+        self.remove(why)
+        self.dither()
+
+    def answer_why(self, v1, v2, v_sum):
+        randy = Randolph(color = PINK)
+        randy.shift(-randy.get_bottom())
+        self.remove(v1, v2, v_sum)
+        for v in v1, v2, v_sum:
+            self.add(v)
+            self.show_ghost_movement(v)
+            self.remove(v)
+        self.add(v1, v2 )
+        self.dither()
+        self.play(ApplyMethod(randy.scale, 0.3))
+        self.play(ApplyMethod(randy.shift, v1.get_end()))
+        self.dither()
+        self.play(ApplyMethod(v2.shift, v1.get_end()))
+        self.play(ApplyMethod(randy.move_to, v2.get_end()))
+        self.dither()
+        self.remove(randy)
+        randy.move_to(ORIGIN)
+        self.play(FadeIn(v_sum))
+        self.play(ApplyMethod(randy.shift, v_sum.get_end()))
+        self.dither()
+
+
+class AddingNumbersOnNumberLine(Scene):
+    def construct(self):
+        number_line = NumberLine()
+        number_line.add_numbers()
+        two_vect = Vector([2, 0])
+        five_vect = Vector([5, 0], color = MAROON_B)
+        seven_vect = Vector([7, 0], color = PINK)
+        five_vect.shift(two_vect.get_end())
+        seven_vect.shift(0.5*DOWN)
+        vects = [two_vect, five_vect, seven_vect]
+
+        two, five, seven = map(TexMobject, ["2", "5", "7"])
+        two.next_to(two_vect, UP)
+        five.next_to(five_vect, UP)
+        seven.next_to(seven_vect, DOWN)
+        nums = [two, five, seven]
+
+        sum_mob = TexMobject("2 + 5").shift(3*UP)
+
+        self.play(ShowCreation(number_line, submobject_mode = "one_at_a_time"))
+        self.dither()
+        self.play(Write(sum_mob, run_time = 2))
+        self.dither()
+        for vect, num in zip(vects, nums):
+            self.play(
+                ShowCreation(vect, submobject_mode = "one_at_a_time"),
+                Write(num, run_time = 1)
+            )
+            self.dither()
+
+
+class VectorAdditionNumerically(VectorScene):
+    def construct(self):
+        plus = TexMobject("+")
+        equals = TexMobject("=")
+        randy = Randolph()
+        randy.scale_to_fit_height(1)
+        randy.shift(-randy.get_bottom())
+
+        axes = self.add_axes()
+        x_axis, y_axis = axes.split()
+
+        v1 = self.add_vector([1, 2])
+        coords1, x_line1, y_line1 = self.vector_to_coords(v1, cleanup = False)
+        self.play(ApplyFunction(
+            lambda m : m.next_to(y_axis, RIGHT).to_edge(UP),
+            coords1
+        ))
+        plus.next_to(coords1, RIGHT)
+
+        v2 = self.add_vector([3, -1], color = MAROON_B)
+        coords2, x_line2, y_line2 = self.vector_to_coords(v2, cleanup = False)
+        self.dither()
+        self.play(
+            ApplyMethod(coords2.next_to, plus, RIGHT),
+            Write(plus, run_time = 1), 
+            *[
+                ApplyMethod(mob.shift, v1.get_end())
+                for mob in v2, x_line2, y_line2
+            ]
+        )
+        equals.next_to(coords2, RIGHT)
+        self.dither()
+
+        self.play(FadeIn(randy))
+        for step in [RIGHT, 2*UP, 3*RIGHT, DOWN]:
+            self.play(ApplyMethod(randy.shift, step, run_time = 1.5))
+        self.dither()
+        self.play(ApplyMethod(randy.shift, -randy.get_bottom()))
+
+        self.play(ApplyMethod(x_line2.shift, 2*DOWN))
+        self.play(ApplyMethod(y_line1.shift, 3*RIGHT))
+        for step in [4*RIGHT, 2*UP, DOWN]:
+            self.play(ApplyMethod(randy.shift, step))
+        self.play(FadeOut(randy))
+        self.remove(randy)
+        one_brace = Brace(x_line1)
+        three_brace = Brace(x_line2)
+        one = TexMobject("1").next_to(one_brace, DOWN)
+        three = TexMobject("3").next_to(three_brace, DOWN)
+        self.play(
+            GrowFromCenter(one_brace),
+            GrowFromCenter(three_brace),
+            Write(one),
+            Write(three),
+            run_time = 1
+        )
+        self.dither()
+
+        two_brace = Brace(y_line1, RIGHT)
+        two = TexMobject("2").next_to(two_brace, RIGHT)
+        new_y_line = Line(4*RIGHT, 4*RIGHT+UP, color = Y_COLOR)
+        two_minus_one_brace = Brace(new_y_line, RIGHT)
+        two_minus_one = TexMobject("2+(-1)").next_to(two_minus_one_brace, RIGHT)
+        self.play(
+            GrowFromCenter(two_brace),
+            Write(two, run_time = 1)
+        )
+        self.dither()
+        self.play(
+            Transform(two_brace, two_minus_one_brace),
+            Transform(two, two_minus_one),
+            Transform(y_line1, new_y_line),
+            Transform(y_line2, new_y_line)
+        )
+        self.dither()
+        self.add_vector(v2.get_end(), color = PINK )
+
+        sum_coords = Matrix(["1+3", "2+(-1)"])
+        sum_coords.scale_to_fit_height(coords1.get_height())
+        sum_coords.next_to(equals, RIGHT)
+        brackets = sum_coords.get_brackets()
+        x1, y1 = coords1.get_mob_matrix().flatten()
+        x2, y2 = coords2.get_mob_matrix().flatten()
+        sum_x, sum_y = sum_coords.get_mob_matrix().flatten()
+        sum_x_start = VMobject(x1, x2).copy()
+        sum_y_start = VMobject(y1, y2).copy()
+        self.play(
+            Write(brackets),
+            Write(equals),
+            Transform(sum_x_start, sum_x),
+            run_time = 1
+        )
+        self.play(Transform(sum_y_start, sum_y))
+        self.dither(2)
+
+        starters = [x1, y1, x2, y2, sum_x_start, sum_y_start]
+        variables = map(TexMobject, [
+            "x_1", "y_1", "x_2", "y_2", "x_1+y_1", "x_2+y_2"
+        ])
+        for i, (var, starter) in enumerate(zip(variables, starters)):
+            if i%2 == 0:
+                var.highlight(X_COLOR)
+            else:
+                var.highlight(Y_COLOR)
+            var.scale(VECTOR_LABEL_SCALE_VAL)
+            var.move_to(starter)
+        self.play(
+            Transform(
+                VMobject(*starters[:4]), 
+                VMobject(*variables[:4])
+            ),
+            FadeOut(sum_x_start), 
+            FadeOut(sum_y_start)
+        )
+        sum_x_end, sum_y_end = variables[-2:]
+        self.dither(2)
+        self.play(
+            Transform(VMobject(x1, x2).copy(), sum_x_end)
+        )
+        self.play(
+            Transform(VMobject(y1, y2).copy(), sum_y_end)
+        )
+        self.dither(3)
+
+class MultiplicationByANumberIntro(Scene):
+    def construct(self):
+        v = TexMobject("\\vec{\\textbf{v}}")
+        v.highlight(YELLOW)
+        nums = map(TexMobject, ["2", "\\dfrac{1}{3}", "-1.8"])
+        for mob in [v] + nums:
+            mob.scale(1.5)
+
+        self.play(Write(v, run_time = 1))
+        last = None
+        for num in nums:
+            num.next_to(v, LEFT)
+            if last:
+                self.play(Transform(last, num))
+            else:
+                self.play(FadeIn(num))
+                last = num
+            self.dither()
+
+class ShowScalarMultiplication(VectorScene):
+    def construct(self):
+        plane = self.add_plane()
+        v = self.add_vector([3, 1])
+        label = self.label_vector(v, "v", add_to_vector = False)
+
+        self.scale_vector(v, 2, label)
+        self.scale_vector(v, 1./3, label, factor_tex = "\\dfrac{1}{3}")
+        self.scale_vector(v, -1.8, label)
+        self.remove(label)
+        self.describe_scalars(v, plane)
+
+
+    def scale_vector(self, v, factor, v_label, 
+                     v_name = "v", factor_tex = None):
+        starting_mobjects = list(self.mobjects)
+
+        if factor_tex is None:
+            factor_tex = str(factor)
+        scaled_vector = self.add_vector(
+            factor*v.get_end(), animate = False
+        )
+        self.remove(scaled_vector)
+        label_tex = "%s\\vec{\\textbf{%s}}"%(factor_tex, v_name)
+        label = self.label_vector(
+            scaled_vector, label_tex, animate = False,
+            add_to_vector = False
+        )
+        self.remove(label)
+        factor_mob = TexMobject(factor_tex)
+        if factor_mob.get_height() > 1:
+            factor_mob.scale_to_fit_height(0.9)
+        if factor_mob.get_width() > 1:
+            factor_mob.scale_to_fit_width(0.9)
+        factor_mob.shift(1.5*RIGHT+2.5*UP)
+
+        num_factor_parts = len(factor_mob.split())
+        factor_mob_parts_in_label = label.split()[:num_factor_parts]
+        label_remainder_parts = label.split()[num_factor_parts:]
+        factor_in_label = VMobject(*factor_mob_parts_in_label)
+        label_remainder = VMobject(*label_remainder_parts)
+
+
+        self.play(Write(factor_mob, run_time = 1))
+        self.dither()
+        self.play(
+            ApplyMethod(v.copy().highlight, DARK_GREY),
+            ApplyMethod(v_label.copy().highlight, DARK_GREY),
+            Transform(factor_mob, factor_in_label),
+            Transform(v.copy(), scaled_vector),
+            Transform(v_label.copy(), label_remainder),
+        )
+        self.dither(2)
+
+        self.clear()
+        self.add(*starting_mobjects)
+
+    def describe_scalars(self, v, plane):
+        axes = plane.get_axes()
+        long_v = Vector(2*v.get_end())
+        long_minus_v = Vector(-2*v.get_end())
+        original_v = v.copy()
+        scaling_word = TextMobject("``Scaling''").to_corner(UP+LEFT)
+        scaling_word.shift(2*RIGHT)
+        scalars = VMobject(*map(TexMobject, [
+            "2,", "\\dfrac{1}{3},", "-1.8,", "\\dots"
+        ]))
+        scalars.arrange_submobjects(RIGHT, buff = 0.4)
+        scalars.next_to(scaling_word, DOWN, aligned_edge = LEFT)
+        scalars_word = TextMobject("``Scalars''")
+        scalars_word.next_to(scalars, DOWN, aligned_edge = LEFT)
+
+        self.remove(plane)
+        self.add(axes)
+        self.play(
+            Write(scaling_word),
+            Transform(v, long_v),
+            run_time = 1.5
+        )
+        self.play(Transform(v, long_minus_v, run_time = 3))
+        self.play(Write(scalars))
+        self.dither()
+        self.play(Write(scalars_word))
+        self.play(Transform(v, original_v), run_time = 3)
+        self.dither(2)
+
+class ScalingNumerically(VectorScene):
+    def construct(self):
+        two_dot = TexMobject("2\\cdot")
+        equals = TexMobject("=")
+        self.add_axes()
+        v = self.add_vector([3, 1])
+        v_coords, vx_line, vy_line = self.vector_to_coords(v, cleanup = False)
+        self.play(ApplyMethod(v_coords.to_edge, UP))
+        two_dot.next_to(v_coords, LEFT)
+        equals.next_to(v_coords, RIGHT)
+        two_v = self.add_vector([6, 2], animate = False)
+        self.remove(two_v)
+        self.play(
+            Transform(v.copy(), two_v), 
+            Write(two_dot, run_time = 1)
+        )
+        two_v_coords, two_v_x_line, two_v_y_line = self.vector_to_coords(
+            two_v, cleanup = False
+        )
+        self.play(
+            ApplyMethod(two_v_coords.next_to, equals, RIGHT),
+            Write(equals, run_time = 1)
+        )
+        self.dither(2)
+
+        x, y = v_coords.get_mob_matrix().flatten()
+        two_v_elems = two_v_coords.get_mob_matrix().flatten()
+        x_sym, y_sym = map(TexMobject, ["x", "y"])
+        two_x_sym, two_y_sym = map(TexMobject, ["2x", "2y"])
+        VMobject(x_sym, two_x_sym).highlight(X_COLOR)
+        VMobject(y_sym, two_y_sym).highlight(Y_COLOR)
+        syms = [x_sym, y_sym, two_x_sym, two_y_sym]
+        VMobject(*syms).scale(VECTOR_LABEL_SCALE_VAL)
+        for sym, num in zip(syms, [x, y] + list(two_v_elems)):
+            sym.move_to(num)
+        self.play(
+            Transform(x, x_sym),
+            Transform(y, y_sym),
+            FadeOut(VMobject(*two_v_elems))
+        )
+        self.dither()
+        self.play(
+            Transform(
+                VMobject(two_dot.copy(), x.copy()),
+                two_x_sym
+            ),
+            Transform(
+                VMobject(two_dot.copy(), y.copy() ),
+                two_y_sym
+            )
+        )
+        self.dither(2)
+
+
+
+class FollowingVideos(UpcomingSeriesOfVidoes):
+    def construct(self):
+        v_sum = VMobject(
+            Vector([1, 1], color = YELLOW),
+            Vector([3, 1], color = BLUE).shift(RIGHT+UP),
+            Vector([4, 2], color = GREEN),
+        )
+        scalar_multiplication = VMobject(
+            TexMobject("2 \\cdot "),
+            Vector([1, 1]),
+            TexMobject("="),
+            Vector([2, 2], color = WHITE)
+        )
+        scalar_multiplication.arrange_submobjects(RIGHT)
+        both = VMobject(v_sum, scalar_multiplication)
+        both.arrange_submobjects(RIGHT, buff = 1)
+        both.shift(2*DOWN)
+        self.add(both)
+
+        UpcomingSeriesOfVidoes.construct(self)
+        last_video = self.mobjects[-1]
+        self.play(ApplyMethod(last_video.highlight, YELLOW))
+        self.dither()
+        everything = VMobject(*self.mobjects)
+        everything.remove(last_video)
+        big_last_video = last_video.copy()
+        big_last_video.center()
+        big_last_video.scale_to_fit_height(2.5*SPACE_HEIGHT)
+        big_last_video.set_fill(opacity = 0)
+        self.play(
+            ApplyMethod(everything.shift, 2*SPACE_WIDTH*LEFT),
+            Transform(last_video, big_last_video),
+            run_time = 2
+        )
 
-    def answer_why(self):
-        pass
 
 
 class ItDoesntMatterWhich(Scene):
@@ -736,6 +1164,137 @@ class ItDoesntMatterWhich(Scene):
             Transform(physy_statement, back_and_forth)
         )
         self.dither()
+
+
+class DataAnalyst(Scene):
+    def construct(self):
+        plane = NumberPlane()
+        ellipse = ParametricFunction(
+            lambda x : 2*np.cos(x)*(UP+RIGHT) + np.sin(x)*(UP+LEFT),
+            color = PINK, 
+            t_max = 2*np.pi
+        )
+        ellipse_points = [
+            ellipse.point_from_proportion(x)
+            for x in np.arange(0, 1, 1./20)
+        ]
+        string_vects = [
+            matrix_to_mobject(("%.02f %.02f"%tuple(ep[:2])).split())
+            for ep in ellipse_points
+        ]
+        string_vects_matrix = Matrix(
+            np.array(string_vects).reshape((4, 5))
+        )
+        string_vects = string_vects_matrix.get_mob_matrix().flatten()
+        string_vects = VMobject(*string_vects)
+
+        vects = VMobject(*map(Vector, ellipse_points))
+
+        self.play(Write(string_vects))
+        self.dither(2)
+        self.play(
+            FadeIn(plane),
+            Transform(string_vects, vects)
+        )
+        self.remove(string_vects)
+        self.add(vects)
+        self.dither()
+        self.play(
+            ApplyMethod(plane.fade, 0.7),
+            ApplyMethod(vects.highlight, DARK_GREY),
+            ShowCreation(ellipse)
+        )
+        self.dither(3)
+
+
+class ManipulateSpace(LinearTransformationScene):
+    CONFIG = {
+        "include_background_plane" : False,
+        "show_basis_vectors" : False,
+    }
+
+    def construct(self):
+        matrix_rule = TexMobject("""
+            \\left[
+                \\begin{array}{c}
+                    x \\\\ y
+                \\end{array}
+            \\right]
+            \\rightarrow
+            \\left[
+                \\begin{array}{c}
+                    2x + y \\\\ y + 2x
+                \\end{array}
+            \\right]
+        """)
+
+        self.setup()
+        pi_creature = PiCreature(color = PINK).scale(0.5)
+        pi_creature.shift(-pi_creature.get_corner(DOWN+LEFT))
+        self.plane.prepare_for_nonlinear_transform()
+
+        def homotopy(x, y, z, t):
+            norm = np.linalg.norm([x, y])
+            tau = interpolate(5, -5, t) + norm/SPACE_WIDTH
+            alpha = sigmoid(tau)
+            return [x, y + 0.5*np.sin(2*np.pi*alpha), z]
+
+        self.play(ShowCreation(
+            self.plane, 
+            submobject_mode = "one_at_a_time",
+            run_time = 2
+        ))
+        self.play(FadeIn(pi_creature))
+        self.play(Blink(pi_creature))
+        self.plane.add(pi_creature)
+        self.play(Homotopy(homotopy, self.plane, run_time = 3))
+        self.dither(2)
+        self.apply_matrix([[2, 1], [1, 2]])
+        self.dither()
+        self.play(
+            FadeOut(self.plane),
+            Write(matrix_rule),
+            run_time = 2
+        )
+        self.dither()
+
+class CodingMathyAnimation(Scene):
+    pass
+
+class NextVideo(Scene):
+    def construct(self):
+        title = TextMobject("Next video: Linear combinations, span, and bases")
+        title.to_edge(UP)
+        rect = Rectangle(width = 16, height = 9, color = BLUE)
+        rect.scale_to_fit_height(6)
+        rect.next_to(title, DOWN)
+
+        self.add(title)
+        self.play(ShowCreation(rect))
+        self.dither()    
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
 
 
 

eola/chapter2.py

@@ -0,0 +1,99 @@
+from mobject.tex_mobject import TexMobject
+from mobject import Mobject
+from mobject.image_mobject import ImageMobject
+from mobject.vectorized_mobject import VMobject
+
+from animation.animation import Animation
+from animation.transform import *
+from animation.simple_animations import *
+from animation.playground import *
+from topics.geometry import *
+from topics.characters import *
+from topics.functions import *
+from topics.number_line import *
+from topics.combinatorics import *
+from scene import Scene
+from camera import Camera
+from mobject.svg_mobject import *
+from mobject.tex_mobject import *
+from mobject.vectorized_mobject import *
+
+from eola.matrix import *
+from eola.two_d_space import *
+
+class OpeningQuote(Scene):
+    def construct(self):
+        words = TextMobject("""
+            Mathematics requires a small dose, not of genius, \\\\
+            but of an imaginative freedom which, in a larger \\\\
+            dose, would be insanity.
+        """)
+        words.to_edge(UP)    
+        for mob in words.submobjects[49:49+18]:
+            mob.highlight(GREEN)
+        words.show()
+        author = TextMobject("-Angus K. Rodgers")
+        author.highlight(YELLOW)
+        author.next_to(words, DOWN, buff = 0.5)
+
+        self.play(FadeIn(words))
+        self.dither(3)
+        self.play(Write(author, run_time = 3))
+        self.dither()
+
+
+class CoordinatesWereFamiliar(TeacherStudentsScene):
+    def construct(self):
+        self.setup()
+        self.student_says("I know this already")
+        self.random_blink()
+        self.teacher_says("Ah, but there is a subtlety")
+        self.random_blink()
+        self.dither()
+
+
+class CoordinatesAsScalars(VectorScene):
+    def construct(self):
+        self.add_axes()
+        vector = self.add_vector([3, -2])
+        array, x_line, y_line = self.vector_to_coords(vector)
+        self.add(array)
+        self.dither()
+        self.general_idea_of_scalars(array)
+
+    def general_idea_of_scalars(self, array):
+        starting_mobjects = self.get_mobjects()
+        starting_mobjects.remove(array)
+
+        title = TextMobject("Think of each coordinate as a scalar")
+        title.to_edge(UP)
+
+        x, y = array.get_mob_matrix().flatten()
+        new_x = x.copy().scale(2).highlight(X_COLOR)
+        new_x.move_to(3*LEFT+2*UP)
+        new_y = y.copy().scale(2).highlight(Y_COLOR)
+        new_y.move_to(3*RIGHT+2*UP)
+
+        self.play(
+            FadeOut(*starting_mobjects)
+            Transform(x, new_x),
+            Transform(y, new_y),
+            Write(title),
+        )
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+

eola/matrix.py

@@ -7,17 +7,13 @@ from mobject.tex_mobject import TexMobject, TextMobject
 from animation.transform import ApplyPointwiseFunction, Transform, \
     ApplyMethod, FadeOut, ApplyFunction
 from animation.simple_animations import ShowCreation, Write
-from topics.number_line import NumberPlane
-from topics.geometry import Vector, Line, Circle, Arrow
+from topics.number_line import NumberPlane, Axes
+from topics.geometry import Vector, Line, Circle, Arrow, Dot
 
 from helpers import *
 
 VECTOR_LABEL_SCALE_VAL = 0.7
 
-X_COLOR = GREEN_C
-Y_COLOR = RED_C
-Z_COLOR = BLUE_D
-
 def matrix_to_tex_string(matrix):
     matrix = np.array(matrix).astype("string")
     if matrix.ndim == 1:
@@ -52,94 +48,6 @@ def vector_coordinate_label(vector_mob, integer_labels = True, n_dim = 2):
     label.shift(shift_dir)
     return label
 
-
-class LinearTransformationScene(Scene):
-    CONFIG = {
-        "include_background_plane" : True,
-        "include_foreground_plane" : True,
-        "foreground_plane_kwargs" : {
-            "x_radius" : 2*SPACE_WIDTH,
-            "y_radius" : 2*SPACE_HEIGHT,
-            "secondary_line_ratio" : 0
-        },
-        "background_plane_kwargs" : {
-            "color" : GREY,
-            "secondary_color" : DARK_GREY,
-            "axes_color" : GREY,
-        },
-        "show_coordinates" : False,
-        "show_basis_vectors" : True,
-        "i_hat_color" : GREEN_B,
-        "j_hat_color" : RED,
-    }
-    def setup(self):
-        self.background_mobjects = []
-        self.transformable_mobject = []
-        self.moving_vectors = []
-
-        self.background_plane = NumberPlane(
-            **self.background_plane_kwargs
-        )
-
-        if self.show_coordinates:
-            self.background_plane.add_coordinates()
-        if self.include_background_plane:                
-            self.add_background_mobject(self.background_plane)
-        if self.include_foreground_plane:
-            self.plane = NumberPlane(**self.foreground_plane_kwargs)
-            self.add_transformable_mobject(self.plane)
-        if self.show_basis_vectors:
-            self.add_vector((1, 0), self.i_hat_color)
-            self.add_vector((0, 1), self.j_hat_color)
-
-    def add_background_mobject(self, *mobjects):
-        for mobject in mobjects:
-            if mobject not in self.background_mobjects:
-                self.background_mobjects.append(mobject)
-                self.add(mobject)
-            
-    def add_transformable_mobject(self, *mobjects):
-        for mobject in mobjects:
-            if mobject not in self.transformable_mobject:
-                self.transformable_mobject.append(mobject)
-                self.add(mobject)
-
-    def add_vector(self, coords, color = YELLOW):
-        vector = Vector(self.background_plane.num_pair_to_point(coords))
-        vector.highlight(color)
-        self.moving_vectors.append(vector)
-        return vector
-
-    def apply_matrix(self, matrix, **kwargs):
-        matrix = np.array(matrix)
-        if matrix.shape == (2, 2):
-            new_matrix = np.identity(3)
-            new_matrix[:2, :2] = matrix
-            matrix = new_matrix
-        elif matrix.shape != (3, 3):
-            raise "Matrix has bad dimensions"
-        transpose = np.transpose(matrix)
-
-        def func(point):
-            return np.dot(point, transpose)
-
-        new_vectors = [
-            Vector(func(v.get_end()), color = v.get_stroke_color())
-            for v in self.moving_vectors
-        ]
-        self.play(
-            ApplyPointwiseFunction(
-                func,
-                VMobject(*self.transformable_mobject),
-                **kwargs
-            ),
-            Transform(
-                VMobject(*self.moving_vectors),
-                VMobject(*new_vectors), 
-                **kwargs
-            )
-        )
-
 class Matrix(VMobject):
     CONFIG = {
         "v_buff" : 0.5,
@@ -327,145 +235,6 @@ class NumericalMatrixMultiplication(Scene):
 
 
 
-class VectorScene(Scene):
-    def add_plane(self, animate = False, **kwargs):
-        plane = NumberPlane(**kwargs)
-        if animate:
-            self.play(ShowCreation(plane, submobject_mode = "lagged_start"))
-        self.add(plane)
-        return plane
-
-    def add_vector(self, vector, animate = True, color = YELLOW):
-        arrow = Vector(vector, color = color)
-        if animate:
-            self.play(ShowCreation(arrow, submobject_mode = "one_at_a_time"))
-        self.add(arrow)
-        return arrow
-
-    def label_vector(self, vector, label, animate = True, 
-                     direction = "left", rotate = False,
-                     color = WHITE, add_to_vector = True,
-                     buff_factor = 1.5):
-        if len(label) == 1:
-            label = "\\vec{\\textbf{%s}}"%label
-        label = TexMobject(label)
-        label.highlight(color)        
-        label.scale(VECTOR_LABEL_SCALE_VAL)
-        if rotate:
-            label.rotate(vector.get_angle())
-
-        vector_vect = vector.get_end() - vector.get_start()
-        if direction is "left":
-            rot_angle = -np.pi/2
-        else:
-            rot_angle = np.pi/2
-        label.shift(-buff_factor*label.get_boundary_point(
-            rotate_vector(vector_vect, rot_angle)
-        ))
-        label.shift(vector.get_center())
-
-        if add_to_vector:
-            vector.add(label)
-        if animate:
-            self.play(Write(label, run_time = 1))
-        self.add(label)
-        return label
-
-    def position_x_coordinate(self, x_coord, x_line, vector):
-        x_coord.next_to(x_line, -vector[1]*UP)
-        x_coord.highlight(X_COLOR)
-        return x_coord
-
-    def position_y_coordinate(self, y_coord, y_line, vector):
-        y_coord.next_to(y_line, vector[0]*RIGHT)
-        y_coord.highlight(Y_COLOR)
-        return y_coord
-
-    def coords_to_vector(self, vector, coords_start = 2*RIGHT+2*UP, cleanup = True):
-        starting_mobjects = list(self.mobjects)
-        array = Matrix(vector)
-        array.shift(coords_start)
-        arrow = Vector(vector)
-        x_line = Line(ORIGIN, vector[0]*RIGHT)
-        y_line = Line(x_line.get_end(), arrow.get_end())
-        x_line.highlight(X_COLOR)
-        y_line.highlight(Y_COLOR)
-        x_coord, y_coord = array.get_mob_matrix().flatten()
-
-        self.play(Write(array, run_time = 1))
-        self.dither()
-        self.play(ApplyFunction(
-            lambda x : self.position_x_coordinate(x, x_line, vector),
-            x_coord
-        ))
-        self.play(ShowCreation(x_line))
-        self.play(
-            ApplyFunction(
-                lambda y : self.position_y_coordinate(y, y_line, vector),
-                y_coord
-            ),
-            FadeOut(array.get_brackets())
-        )
-        self.play(ShowCreation(y_line))
-        self.play(ShowCreation(arrow, submobject_mode = "one_at_a_time"))
-        self.dither()
-        if cleanup:
-            self.clear()
-            self.add(*starting_mobjects)
-
-    def vector_to_coords(self, vector, integer_labels = True, cleanup = True):
-        starting_mobjects = list(self.mobjects)
-        show_creation = False
-        if isinstance(vector, Arrow):
-            arrow = vector
-            vector = arrow.get_end()[:2]
-        else:
-            arrow = Vector(vector)
-            show_creation = True
-        array = vector_coordinate_label(arrow, integer_labels = integer_labels)
-        x_line = Line(ORIGIN, vector[0]*RIGHT)
-        y_line = Line(x_line.get_end(), arrow.get_end())
-        x_line.highlight(X_COLOR)
-        y_line.highlight(Y_COLOR)
-        x_coord, y_coord = array.get_mob_matrix().flatten()
-        x_coord_start = self.position_x_coordinate(
-            x_coord.copy(), x_line, vector
-        )
-        y_coord_start = self.position_y_coordinate(
-            y_coord.copy(), y_line, vector
-        )
-        brackets = array.get_brackets()
-
-        if show_creation:
-            self.play(ShowCreation(arrow, submobject_mode = "one_at_a_time"))
-        self.play(
-            ShowCreation(x_line),
-            Write(x_coord_start),
-            run_time = 1
-        )
-        self.play(
-            ShowCreation(y_line),
-            Write(y_coord_start),
-            run_time = 1
-        )
-        self.dither()
-        self.play(
-            Transform(x_coord_start, x_coord),
-            Transform(y_coord_start, y_coord),
-            Write(brackets),
-            run_time = 1
-        )
-        self.dither()
-
-        self.remove(x_coord_start, y_coord_start)
-        self.add(x_coord, y_coord)
-        if cleanup:
-            self.clear()
-            self.add(*starting_mobjects)
-
-
-
-
 
 
 

eola/two_d_space.py

@@ -0,0 +1,294 @@
+import numpy as np
+
+from scene import Scene
+from mobject import Mobject
+from mobject.vectorized_mobject import VMobject
+from mobject.tex_mobject import TexMobject, TextMobject
+from animation.transform import ApplyPointwiseFunction, Transform, \
+    ApplyMethod, FadeOut, ApplyFunction
+from animation.simple_animations import ShowCreation, Write
+from topics.number_line import NumberPlane, Axes
+from topics.geometry import Vector, Line, Circle, Arrow, Dot
+
+from helpers import *
+from eola.matrix import Matrix, VECTOR_LABEL_SCALE_VAL, vector_coordinate_label
+
+
+X_COLOR = GREEN_C
+Y_COLOR = RED_C
+Z_COLOR = BLUE_D
+
+
+class LinearTransformationScene(Scene):
+    CONFIG = {
+        "include_background_plane" : True,
+        "include_foreground_plane" : True,
+        "foreground_plane_kwargs" : {
+            "x_radius" : 2*SPACE_WIDTH,
+            "y_radius" : 2*SPACE_HEIGHT,
+            "secondary_line_ratio" : 0
+        },
+        "background_plane_kwargs" : {
+            "color" : GREY,
+            "secondary_color" : DARK_GREY,
+            "axes_color" : GREY,
+        },
+        "show_coordinates" : False,
+        "show_basis_vectors" : True,
+        "i_hat_color" : X_COLOR,
+        "j_hat_color" : Y_COLOR,
+    }
+    def setup(self):
+        self.background_mobjects = []
+        self.transformable_mobject = []
+        self.moving_vectors = []
+
+        self.background_plane = NumberPlane(
+            **self.background_plane_kwargs
+        )
+
+        if self.show_coordinates:
+            self.background_plane.add_coordinates()
+        if self.include_background_plane:                
+            self.add_background_mobject(self.background_plane)
+        if self.include_foreground_plane:
+            self.plane = NumberPlane(**self.foreground_plane_kwargs)
+            self.add_transformable_mobject(self.plane)
+        if self.show_basis_vectors:
+            self.add_vector((1, 0), self.i_hat_color)
+            self.add_vector((0, 1), self.j_hat_color)
+
+    def add_background_mobject(self, *mobjects):
+        for mobject in mobjects:
+            if mobject not in self.background_mobjects:
+                self.background_mobjects.append(mobject)
+                self.add(mobject)
+            
+    def add_transformable_mobject(self, *mobjects):
+        for mobject in mobjects:
+            if mobject not in self.transformable_mobject:
+                self.transformable_mobject.append(mobject)
+                self.add(mobject)
+
+    def add_vector(self, coords, color = YELLOW):
+        vector = Vector(self.background_plane.num_pair_to_point(coords))
+        vector.highlight(color)
+        self.moving_vectors.append(vector)
+        return vector
+
+    def apply_matrix(self, matrix, **kwargs):
+        matrix = np.array(matrix)
+        if matrix.shape == (2, 2):
+            new_matrix = np.identity(3)
+            new_matrix[:2, :2] = matrix
+            matrix = new_matrix
+        elif matrix.shape != (3, 3):
+            raise "Matrix has bad dimensions"
+        transpose = np.transpose(matrix)
+
+        def func(point):
+            return np.dot(point, transpose)
+
+        new_vectors = [
+            Vector(func(v.get_end()), color = v.get_stroke_color())
+            for v in self.moving_vectors
+        ]
+        self.play(
+            ApplyPointwiseFunction(
+                func,
+                VMobject(*self.transformable_mobject),
+                **kwargs
+            ),
+            Transform(
+                VMobject(*self.moving_vectors),
+                VMobject(*new_vectors), 
+                **kwargs
+            )
+        )
+
+
+
+
+class VectorScene(Scene):
+    def add_plane(self, animate = False, **kwargs):
+        plane = NumberPlane(**kwargs)
+        if animate:
+            self.play(ShowCreation(plane, submobject_mode = "lagged_start"))
+        self.add(plane)
+        return plane
+
+    def add_axes(self, animate = False, color = WHITE, **kwargs):
+        axes = Axes(color = color)
+        if animate:
+            self.play(ShowCreation(axes, submobject_mode = "one_at_a_time"))
+        self.add(axes)
+        return axes
+
+    def add_vector(self, vector, animate = True, color = YELLOW):
+        arrow = Vector(vector, color = color)
+        if animate:
+            self.play(ShowCreation(arrow, submobject_mode = "one_at_a_time"))
+        self.add(arrow)
+        return arrow
+
+    def get_basis_vectors(self):
+        i_hat = Vector([1, 0], color = X_COLOR)
+        j_hat = Vector([0, 1], color = Y_COLOR)
+        return i_hat, j_hat
+
+    def label_vector(self, vector, label, animate = True, 
+                     direction = "left", rotate = False,
+                     color = WHITE, add_to_vector = True,
+                     buff_factor = 1.5):
+        if len(label) == 1:
+            label = "\\vec{\\textbf{%s}}"%label
+        label = TexMobject(label)
+        label.highlight(color)        
+        label.scale(VECTOR_LABEL_SCALE_VAL)
+        if rotate:
+            label.rotate(vector.get_angle())
+
+        vector_vect = vector.get_end() - vector.get_start()
+        if direction is "left":
+            rot_angle = -np.pi/2
+        else:
+            rot_angle = np.pi/2
+        label.shift(-buff_factor*label.get_boundary_point(
+            rotate_vector(vector_vect, rot_angle)
+        ))
+        label.shift(vector.get_center())
+
+        if add_to_vector:
+            vector.add(label)
+        if animate:
+            self.play(Write(label, run_time = 1))
+        self.add(label)
+        return label
+
+    def position_x_coordinate(self, x_coord, x_line, vector):
+        x_coord.next_to(x_line, -np.sign(vector[1])*UP)
+        x_coord.highlight(X_COLOR)
+        return x_coord
+
+    def position_y_coordinate(self, y_coord, y_line, vector):
+        y_coord.next_to(y_line, np.sign(vector[0])*RIGHT)
+        y_coord.highlight(Y_COLOR)
+        return y_coord
+
+    def coords_to_vector(self, vector, coords_start = 2*RIGHT+2*UP, cleanup = True):
+        starting_mobjects = list(self.mobjects)
+        array = Matrix(vector)
+        array.shift(coords_start)
+        arrow = Vector(vector)
+        x_line = Line(ORIGIN, vector[0]*RIGHT)
+        y_line = Line(x_line.get_end(), arrow.get_end())
+        x_line.highlight(X_COLOR)
+        y_line.highlight(Y_COLOR)
+        x_coord, y_coord = array.get_mob_matrix().flatten()
+
+        self.play(Write(array, run_time = 1))
+        self.dither()
+        self.play(ApplyFunction(
+            lambda x : self.position_x_coordinate(x, x_line, vector),
+            x_coord
+        ))
+        self.play(ShowCreation(x_line))
+        self.play(
+            ApplyFunction(
+                lambda y : self.position_y_coordinate(y, y_line, vector),
+                y_coord
+            ),
+            FadeOut(array.get_brackets())
+        )
+        self.play(ShowCreation(y_line))
+        self.play(ShowCreation(arrow, submobject_mode = "one_at_a_time"))
+        self.dither()
+        if cleanup:
+            self.clear()
+            self.add(*starting_mobjects)
+
+    def vector_to_coords(self, vector, integer_labels = True, cleanup = True):
+        starting_mobjects = list(self.mobjects)
+        show_creation = False
+        if isinstance(vector, Arrow):
+            arrow = vector
+            vector = arrow.get_end()[:2]
+        else:
+            arrow = Vector(vector)
+            show_creation = True
+        array = vector_coordinate_label(arrow, integer_labels = integer_labels)
+        x_line = Line(ORIGIN, vector[0]*RIGHT)
+        y_line = Line(x_line.get_end(), arrow.get_end())
+        x_line.highlight(X_COLOR)
+        y_line.highlight(Y_COLOR)
+        x_coord, y_coord = array.get_mob_matrix().flatten()
+        x_coord_start = self.position_x_coordinate(
+            x_coord.copy(), x_line, vector
+        )
+        y_coord_start = self.position_y_coordinate(
+            y_coord.copy(), y_line, vector
+        )
+        brackets = array.get_brackets()
+
+        if show_creation:
+            self.play(ShowCreation(arrow, submobject_mode = "one_at_a_time"))
+        self.play(
+            ShowCreation(x_line),
+            Write(x_coord_start),
+            run_time = 1
+        )
+        self.play(
+            ShowCreation(y_line),
+            Write(y_coord_start),
+            run_time = 1
+        )
+        self.dither()
+        self.play(
+            Transform(x_coord_start, x_coord),
+            Transform(y_coord_start, y_coord),
+            Write(brackets),
+            run_time = 1
+        )
+        self.dither()
+
+        self.remove(x_coord_start, y_coord_start)
+        self.add(x_coord, y_coord)
+        if cleanup:
+            self.clear()
+            self.add(*starting_mobjects)
+        return array, x_line, y_line
+
+    def show_ghost_movement(self, vector):
+        if isinstance(vector, Arrow):
+            vector = vector.get_end() - vector.get_start()
+        elif len(vector) == 2:
+            vector = np.append(np.array(vector), 0.0)
+        x_max = int(SPACE_WIDTH + abs(vector[0]))
+        y_max = int(SPACE_HEIGHT + abs(vector[1]))
+        dots = VMobject(*[
+            Dot(x*RIGHT + y*UP)
+            for x in range(-x_max, x_max)
+            for y in range(-y_max, y_max)
+        ])
+        dots.set_fill(BLACK, opacity = 0)
+        dots_halfway = dots.copy().shift(vector/2).set_fill(WHITE, 1)
+        dots_end = dots.copy().shift(vector)
+
+        self.play(Transform(
+            dots, dots_halfway, rate_func = rush_into
+        ))
+        self.play(Transform(
+            dots, dots_end, rate_func = rush_from
+        ))
+        self.remove(dots)
+
+
+
+
+
+
+
+
+
+
+

scene/scene.py

@@ -90,6 +90,7 @@ class Scene(object):
     def remove(self, *mobjects):
         if not all_elements_are_instances(mobjects, Mobject):
             raise Exception("Removing something which is not a mobject")
+        mobjects = it.chain(*[m.submobject_family() for m in mobjects])
         mobjects = filter(lambda m : m in self.mobjects, mobjects)
         if len(mobjects) == 0:
             return
@@ -109,6 +110,12 @@ class Scene(object):
         self.mobjects = []
         return self
 
+    def get_mobjects(self):
+        return list(self.mobjects)
+
+    def get_mobject_copies(self):
+        return [m.copy() for m in self.mobjects]
+
     def align_run_times(self, *animations, **kwargs):
         if "run_time" in kwargs:
             run_time = kwargs["run_time"]

topics/characters.py

@@ -5,7 +5,9 @@ from mobject.svg_mobject import SVGMobject
 from mobject.vectorized_mobject import VMobject
 from mobject.tex_mobject import TextMobject
 
-from animation.transform import ApplyMethod
+from animation.transform import ApplyMethod, FadeOut, FadeIn
+from animation.simple_animations import Write
+from scene import Scene
 
 
 PI_CREATURE_DIR = os.path.join(IMAGE_DIR, "PiCreature")
@@ -92,6 +94,7 @@ class PiCreature(SVGMobject):
         x, y = direction[:2]        
         for pupil, eye in zip(self.pupils.split(), self.eyes.split()):
             pupil.move_to(eye, side_to_align = direction)
+            #Some hacky nudging is required here
             if y > 0 and x != 0: # Look up and to a side
                 nudge_size = pupil.get_height()/4.
                 if x > 0: 
@@ -99,6 +102,9 @@ class PiCreature(SVGMobject):
                 else:
                     nudge = nudge_size*(DOWN+RIGHT)
                 pupil.shift(nudge)
+            elif y < 0:
+                nudge_size = pupil.get_height()/8.
+                pupil.shift(nudge_size*UP)
         return self
 
     def get_looking_direction(self):
@@ -186,7 +192,8 @@ class Bubble(SVGMobject):
         self.content = Mobject()
 
     def get_tip(self):
-        return self.get_corner(DOWN+self.direction)
+        #TODO, find a better way
+        return self.get_corner(DOWN+self.direction)-0.6*self.direction
 
     def get_bubble_center(self):
         return self.get_center() + self.get_height()*UP/8.0
@@ -204,8 +211,8 @@ class Bubble(SVGMobject):
         mob_center = mobject.get_center()
         if (mob_center[0] > 0) != (self.direction[0] > 0):
             self.flip()
-        boundary_point = mobject.get_boundary_point(UP-self.direction)
-        vector_from_center = 1.2*(boundary_point-mob_center)
+        boundary_point = mobject.get_critical_point(UP-self.direction)
+        vector_from_center = 1.0*(boundary_point-mob_center)
         self.move_tip_to(mob_center+vector_from_center)
         return self
 
@@ -256,6 +263,107 @@ class ThoughtBubble(Bubble):
         return self
 
 
+class TeacherStudentsScene(Scene):
+    def setup(self):
+        self.teacher = Mortimer()
+        self.teacher.to_corner(DOWN + RIGHT)
+        self.teacher.look(DOWN+LEFT)
+        self.students = VMobject(*[
+            Randolph(color = c)
+            for c in BLUE_D, BLUE_C, BLUE_E
+        ])
+        self.students.arrange_submobjects(RIGHT)
+        self.students.scale(0.8)
+        self.students.to_corner(DOWN+LEFT)
+
+        for pi_creature in self.get_everyone():
+            pi_creature.bubble = None
+        self.add(*self.get_everyone())
+
+    def get_teacher(self):
+        return self.teacher
+
+    def get_students(self):
+        return self.students.split()
+
+    def get_everyone(self):
+        return [self.get_teacher()] + self.get_students()
+
+    def introduce_bubble(self, content, bubble_type, pi_creature,
+                         content_intro_anim = None,
+                         pi_creature_target_mode = None,
+                         added_anims = []):
+        bubble = pi_creature.get_bubble(bubble_type)
+        if isinstance(content, str):
+            content = TextMobject(content)
+        bubble.position_mobject_inside(content)
+        pi_creature.bubble = bubble        
+
+        content_intro_anim = content_intro_anim or Write(content)
+        run_time = content_intro_anim.run_time
+        one_sec_rate_func = squish_rate_func(
+            smooth, 0, 1./run_time
+        )
+        if not pi_creature_target_mode:
+            if bubble_type is "speech":
+                pi_creature_target_mode = "speaking"
+            else:
+                pi_creature_target_mode = "pondering"
+
+        faders = []
+        to_plains = []
+        for p in self.get_everyone():
+            if p.bubble and p is not pi_creature:
+                faders.append(FadeOut(
+                    p.bubble, rate_func = one_sec_rate_func
+                ))
+                p.bubble = None
+                to_plains.append(ApplyMethod(
+                    p.change_mode, "plain", 
+                    rate_func = one_sec_rate_func
+                ))
+
+        anims = faders + to_plains + added_anims + [
+            content_intro_anim,
+            FadeIn(bubble, rate_func = one_sec_rate_func),
+            ApplyMethod(
+                pi_creature.change_mode, 
+                pi_creature_target_mode,
+                rate_func = one_sec_rate_func
+            ),
+        ]
+        self.play(*anims, run_time = run_time)
+        bubble.add_content(content)
+
+    def teacher_says(self, content, **kwargs):
+        self.introduce_bubble(
+            content, "speech", self.get_teacher(), **kwargs
+        )
+
+    def student_says(self, content, student_index = 1, **kwargs):
+        student = self.get_students()[student_index]
+        self.introduce_bubble(content, "speech", student, **kwargs)
+
+    def teacher_thinks(self, content):
+        self.introduce_bubble(
+            content, "thought", self.get_teacher(), **kwargs
+        )
+
+    def student_thinks(self, content, student_index = 1, **kwargs):
+        student = self.get_students()[student_index]
+        self.introduce_bubble(content, "thought", student, **kwargs)
+
+    def random_blink(self):
+        pi_creature = random.choice(self.get_everyone())
+        self.play(Blink(pi_creature))
+
+
+
+
+
+
+
+