3 changes:   added background color   ensured that turtles appear on the screen when created in the animation sequence   partially removed Vec2D dependence for position
3 changes:
  added background color
  ensured that turtles appear on the screen when created in the animation sequence
  partially removed Vec2D dependence for position

Hasimir/brython,jonathanverner/brython,Hasimir/brython,brython-dev/brython,kikocorreoso/brython,brython-dev/brython,kikocorreoso/brython,Hasimir/brython,jonathanverner/brython,jonathanverner/brython,kikocorreoso/brython,jonathanverner/brython,brython-dev/brython,Hasimir/brython