text: class FixedParticle():
  	def __init__(self, xpos = 0, ypos = 0, radius = 1):
  		self.xpos = xpos
  		self.ypos = ypos
  		self.xvel = xvel
  		self.yvel = yvel
  		self.radius = radius
  	def calculate_interactions_solid(self, s):
  		
  		pass
  		# s is solid that it is interactin with 