func (p *Particle) System() *ParticleSystem {
	return p.system
}
System returns the particle system that p is a part of.
package twodeeparticles
import (
	"image/color"
	"math"
	"time"
)
type Particle struct {
	system         *ParticleSystem
	lifetime       time.Duration
	birthTime      time.Time
	deathTime      time.Time
	lastUpdateTime time.Time
	isAlive  bool
	data     interface{}
	position Vector
	velocity Vector
	scale    Vector
	angle    float64
	color    color.Color
}
func newParticle(s *ParticleSystem) *Particle {
	return &Particle{
		system: s,
		color:  color.White,
	}
}