The previous section uses the default Animation transition. This is a Linear transition, which means that the Widget instance moves from one point to another in a straight line. Invaders trajectories can be more interesting. For example, there could be accelerations, or changes of direction, as the following screenshot shows with the yellow line:
The following is the code of the invader.py:
93. # File name: invader.py 94. from kivy.core.window import Window 95. from kivy.uix.image import Image 96. from kivy.animation import Animation 97. from random import choice, randint 98. from ammo import Missile 99. 100. class Invader(Image): 101. pre_fix = ['in_','out_','in_out_'] 102. functions = ['back','bounce','circ','cubic', 103. 'elastic','expo','quad','quart','quint','sine'] 104. formation = True 105. 106. def solo_attack(self): 107. if self.formation: 108. self.parent.unbind_invader() 109. animation = self.trajectory() 110. ...