(self)
| 55 | a += (G*planet.m/abs(v)**3)*v |
| 56 | return a |
| 57 | def step(self): |
| 58 | dt = self.gravSys.dt |
| 59 | self.setpos(self.pos() + dt*self.v) |
| 60 | if self.gravSys.planets.index(self) != 0: |
| 61 | self.setheading(self.towards(self.gravSys.planets[0])) |
| 62 | self.a = self.acc() |
| 63 | self.v = self.v + dt*self.a |
| 64 | |
| 65 | ## create compound yellow/blue turtleshape for planets |
| 66 |