Particle System

#Libraries
import pygame,sys
from pygame.locals import *
from pygame import gfxdraw
from random import randint as randint
import math

#Initialization of pygame and variables
pygame.init()
xres = int(input("X Resolution:"))
yres = int(input("Y Resolution:"))
g = float(input("Acceleration due to gravity:"))
r = int(input("Particle Radius:"))

#Class containing world settings and info
class wld():
    def __init__(self,x,y,g,r):
        self.x = x
        self.y = y
        self.num = int(input("How Many Balls? (0 for random):"))
        if (self.num == 0):
            self.num = randint(1,1000)
        self.screen = pygame.display.set_mode((x,y))
        self.clock = pygame.time.Clock()
        self.FPS = 60
        self.g = g
        self.bls = []
        self.graphing = False

#Class for particles
class Balls():
#Initialization of particle variables
    def __init__(self):
        self.radius = r
        self.ydisplacement = (world.y/2)
        self.xdisplacement = (world.x/2)
        self.yvelocity = randint(0,50)
        self.xvelocity = randint(-150,150)
        self.xlist = []
        self.ylist = []
        self.time = 0
        self.falltime = 0
        self.bouncetime = 0

#Calculating Motion of particles
    def get_motion(self):
        self.time = self.time + 0.001
        self.falltime = self.falltime + 0.001
        self.bouncetime = self.bouncetime + 0.001
        self.yvelocity = self.yvelocity + 2 * world.g * self.falltime
        self.ydisplacement = self.ydisplacement + self.yvelocity * self.falltime + 0.5 * world.g * self.falltime
        self.xdisplacement = self.xdisplacement + self.xvelocity * self.bouncetime
        if self.xvelocity >= -0.2 and self.xvelocity <= 0.2:
                self.xvelocity = 0

#Calculating bounces along Y axis
    def calc_ybounce(self):
        if self.ydisplacement >= world.y - self.radius:
            self.yvelocity = (-1) * self.yvelocity
            self.ydisplacement = world.y - 1 - self.radius
            if not self.xvelocity == 0 and self.xvelocity >= 0:
                self.xvelocity = self.xvelocity - self.xvelocity/25
            elif not self.xvelocity == 0 and self.xvelocity <= 0:
                self.xvelocity = self.xvelocity - self.xvelocity/25
        if self.ydisplacement <= 0+self.radius:
            self.yvelocity = (-1) * self.yvelocity
            self.ydisplacement = 0+self.radius

#Calculating bounces along X axis
    def calc_xbounce(self):
        if self.xdisplacement >= world.x - self.radius:
            self.xvelocity = (-1) * self.xvelocity
            self.xdisplacement = world.x - self.radius
        if self.xdisplacement <= 0 + self.radius:
            self.xvelocity = (-1) * self.xvelocity
            self.xdisplacement = 0 + self.radius

#Collect particle metrics for plotting
    def tracking(self):
        self.xlist.append(self.xdisplacement + self.radius*2)
        self.ylist.append(self.ydisplacement + self.radius*2)
        if (len(self.xlist)>=2 and world.graphing):
            for x in range(0,len(self.xlist)-2):
                pygame.draw.line(world.screen,(0,255,30),(self.xlist[x],self.ylist[x]),(self.xlist[x+1],self.ylist[x+1]),1)

#Drawing Particles
    def draw(self):
        pygame.gfxdraw.filled_circle(world.screen,int(self.xdisplacement),int(self.ydisplacement),self.radius,(30,0,0))
        pygame.gfxdraw.aacircle(world.screen,int(self.xdisplacement),int(self.ydisplacement),self.radius,(100,0,0))

#Tick event to call other class functions in sequence
    def tick(self):
        self.get_motion()
        self.calc_ybounce()
        self.calc_xbounce()
        self.tracking()
        self.draw()

#Call world and ball classes to initialize and store particles in table.
world = wld(xres,yres,g,r)
for i in range(0,world.num):
    world.bls.append(Balls())

#Main Loop
while True:
#Clock and background
    tick = world.clock.tick(world.FPS)
    world.screen.fill((200,200,200))
#Quit handler
    for event in pygame.event.get():
        if event.type == QUIT:
            pygame.quit()
            sys.exit()
        if event.type == pygame.KEYDOWN and event.key == pygame.K_SPACE:
            if world.graphing:
                world.graphing = False
            else:
                world.graphing = True
#Tick for all particles and update display
    for i in range(0,world.num):
        world.bls[i].tick()
    pygame.display.update()