class Particle:
    def __init__(self,x,y,color,fade_speed):
        self.pos = (x,y)
        self.velocity = (0,0)
        self.accel = (0,0)
        self.surface = None
        self.color = color
        self.fade_speed = fade_speed
        self.alpha = 255

    def set_surface(self,surface):
        self.surface = surface

    def update(self):
        self.velocity = (self.velocity[0]+self.accel[0], self.velocity[1]+self.accel[1])
        self.pos = (self.pos[0] + self.velocity[0], self.pos[1] + self.velocity[1])
        self.accel = (0,0)

    def apply_force(self,force):
        self.accel = (self.accel[0]+force[0],self.accel[1]+force[1])

    def fade(self):
        self.alpha -= self.fade_speed