spider drop code)
- [+] projectile is vertical fireball
- [+] use code similar to snake
- [+] only allowed to shoot if s->bullet = null
- [+] always use open mouth frame if s->bullet
- [+] bullet has initial negative y velocity and is affected by
gravity
- [+] once it is lower than its initial y point, it dies....
- [+] ...and update owner->bullet = null