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# Filename: A11_2D_rotating_tubes.py
# Author: James D. Miller; Gustavus Adolphus College.

import sys, os
import pygame
import datetime
import math

# PyGame Constants
from pygame.locals import *
from pygame.color import THECOLORS

# PyGame gui
from pgu import gui

# Import the vector class from a local module (in this same directory)
from vec2d_jdm import Vec2D

# Networking
from PodSixNet.Server import Server
from PodSixNet.Channel import Channel
import socket

#=====================================================================
# Classes
#=====================================================================

class ClientChannel(Channel):
    def __init__(self, *args, **kwargs):
        Channel.__init__(self, *args, **kwargs)
        pass
    
    # def Network(self, data):
        # #print "Client State Dictionary:", data
        # #print "Network, data['ID']", data['ID']
        # pass
    
    def Network_CN(self, data):
        #global env
        
        # Store incoming data in the client objects.
        speaking_client_name = 'C' + str(data['ID'])
        
        # Check to make sure that this client is still in the client dictionary.
        if speaking_client_name in env.clients:
            # Mouse controls.
        
            env.clients[speaking_client_name].cursor_location_px = data['mXY']  # mouse x,y
            env.clients[speaking_client_name].buttonIsStillDown = data['mBd']   # mouse button down (true/false)
            env.clients[speaking_client_name].mouse_button = data['mB']         # mosue button number (1,2,3,0)
            
            # Jet controls.
            
            # Make the s key behave as a toggle.
            # If key is up, make it ready to accept the down ('D') event.
            if (data['s'] == 'U'):
                env.clients[speaking_client_name].key_s_onoff = 'ON'
                env.clients[speaking_client_name].key_s = data['s']
            # If getting 'D' from network client and the key is enabled.
            elif (env.clients[speaking_client_name].key_s_onoff == 'ON'):
                env.clients[speaking_client_name].key_s = data['s']
                
            env.clients[speaking_client_name].key_a = data['a']
            env.clients[speaking_client_name].key_d = data['d']
            env.clients[speaking_client_name].key_w = data['w']
            
            # Freeze controls.
            env.clients[speaking_client_name].key_f = data['f']
            
            # Gun controls.
            
            # Make the k key behave as a toggle.
            # If key is up, make it ready to accept the down ('D') event.
            if (data['k'] == 'U'):
                env.clients[speaking_client_name].key_k_onoff = 'ON'
                env.clients[speaking_client_name].key_k = data['k']
            # If getting 'D' from network client and the key is enabled.
            elif (env.clients[speaking_client_name].key_k_onoff == 'ON'):
                env.clients[speaking_client_name].key_k = data['k']
            
            env.clients[speaking_client_name].key_j = data['j']
            env.clients[speaking_client_name].key_l = data['l']
            env.clients[speaking_client_name].key_i = data['i']
            env.clients[speaking_client_name].key_space = data[' ']
            
            # Go through the list of client, adding 1 to each that isn't the current SENDING client.
            # Use this to block rendering of objects of clients that have disconnected.
            # Note: this technique will never act to stop rendering the last client's data, because once the last
            # network client disconnects, this counting will stop and it will never reach the limit that inhibits
            # rendering.
            for client_name in env.clients:
                if (client_name != speaking_client_name):
                    env.clients[client_name].Qcount += 1
                else:
                    env.clients[client_name].Qcount = 0
                
                # print client_name, env.clients[client_name].Qcount
            # print "========================================"
                
            
    def Close(self):
        print "A network client game pad has been closed."
     
     
class GameServer(Server):
    channelClass = ClientChannel
    
    def __init__(self, *args, **kwargs):
        Server.__init__(self, *args, **kwargs)
        self.client_count = 0
        pass
        
    # This runs when each client connects.
    def Connected(self, channel, addr):
        #global env
        
        #print 'new connection (channel, addr):', channel, addr
        
        self.client_count += 1
        
        if (self.client_count <= 10):
            channel.Send({"action": "hello", "P_ID":self.client_count})
            client_name = 'C' + str(self.client_count)
            env.clients[client_name] = Client(env.client_colors[client_name])        
        else:
            channel.Send({"action": "hello", "P_ID":0})

        print "self.client_count =", self.client_count

class Client:
    def __init__(self, cursor_color):
        self.cursor_location_px = (0,0)   # x_px, y_px
        self.mouse_button = 1             # 1, 2, or 3
        self.buttonIsStillDown = False        
        
        # Jet
        self.key_a = "U"
        self.key_s = "U"
        self.key_s_onoff = "ON"
        self.key_d = "U"
        self.key_w = "U"
        
        # Gun
        self.key_j = "U"
        self.key_k = "U"
        self.key_k_onoff = "ON"
        self.key_l = "U"
        self.key_i = "U"
        self.key_space = "U"
        
        # Freeze it
        self.key_f = "U"
        
        # Zoom
        self.key_b = "U"
        self.key_n = "U"
        self.key_m = "U"
        self.key_h = "U"
        
        self.selected_puck = None
        self.cursor_color = cursor_color
        self.Qcount = 0
        self.bullet_hit_count = 0
        self.bullet_hit_limit = 150.0
        
        # Define the nature of the cursor strings, one for each mouse button.
        self.mouse_strings = {'string1':{'c_drag':   2.0, 'k_Npm':   60.0},
                              'string2':{'c_drag':   0.2, 'k_Npm':    2.0},
                              'string3':{'c_drag':  20.0, 'k_Npm': 1000.0}}
                              #'string0':{'c_drag':   0.0, 'k_Npm':    0.0}}
                                        
    def calc_string_forces_on_pucks(self):
        # Calculated the string forces on the selected puck and add to the aggregate
        # that is stored in the puck object.
        
        # Only check for a selected puck if one isn't already selected. This keeps
        # the puck from unselecting if cursor is dragged off the puck!
        if (self.selected_puck == None):
            if self.buttonIsStillDown:
                self.selected_puck = air_table.checkForPuckAtThisPosition(self.cursor_location_px)        
        
        else:
            if not self.buttonIsStillDown:
                # Unselect the puck and bomb out of here.
                self.selected_puck.selected = False
                self.selected_puck = None
                return None
            
            # Use dx difference to calculate the hooks law force being applied by the tether line. 
            # If you release the mouse button after a drag it will fling the puck.
            # This tether force will diminish as the puck gets closer to the mouse point.
            dx_2d_m = env.ConvertScreenToWorld(Vec2D(self.cursor_location_px)) - self.selected_puck.pos_2d_m
            
            stringName = "string" + str(self.mouse_button)
            self.selected_puck.cursorString_spring_force_2d_N   += dx_2d_m * self.mouse_strings[stringName]['k_Npm']
            self.selected_puck.cursorString_puckDrag_force_2d_N += (self.selected_puck.vel_2d_mps * 
                                                                    -1 * self.mouse_strings[stringName]['c_drag'])
            
            # # Limit the amount of force the cursor string can apply.
            # mouse_string_tension_limit_N = 1000
            # mouse_string_tension_magnitude = cursor_string.tension_2d_N.length()
            # if mouse_string_tension_magnitude > mouse_string_tension_limit_N:
                # cursor_string.tension_2d_N = (cursor_string.tension_2d_N / mouse_string_tension_magnitude) * mouse_string_tension_limit_N

    def draw_cursor_string(self):
        line_points = [env.ConvertWorldToScreen(self.selected_puck.pos_2d_m), self.cursor_location_px]
        if (self.selected_puck != None):
            pygame.draw.line(game_window.surface, self.cursor_color, line_points[0], line_points[1], 1)
                    
    def draw_fancy_server_cursor(self):
        self.draw_server_cursor( self.cursor_color, 0)
        self.draw_server_cursor( THECOLORS["black"], 1)

    def draw_server_cursor(self, color, edge_px):
        cursor_outline_vertices = []
        cursor_outline_vertices.append(  self.cursor_location_px )
        cursor_outline_vertices.append( (self.cursor_location_px[0] + 10,  self.cursor_location_px[1] + 10) )
        cursor_outline_vertices.append( (self.cursor_location_px[0] +  0,  self.cursor_location_px[1] + 15) )
        
        pygame.draw.polygon(game_window.surface, color, cursor_outline_vertices, edge_px)


        
class Puck:
    def __init__(self, pos_2d_m, radius_m, density_kgpm2, puck_color = THECOLORS["grey"]):
        self.radius_m = radius_m
        self.radius_px = int(round(env.px_from_m(self.radius_m * env.viewZoom)))

        self.density_kgpm2 = density_kgpm2    # mass per unit area
        self.mass_kg = self.density_kgpm2 * math.pi * self.radius_m ** 2
        self.pos_2d_m = pos_2d_m
        self.vel_2d_mps = Vec2D(0.0,0.0)
        
        self.SprDamp_force_2d_N = Vec2D(0.0,0.0)
        self.jet_force_2d_N = Vec2D(0.0,0.0)
        self.cursorString_spring_force_2d_N = Vec2D(0.0,0.0)
        self.cursorString_puckDrag_force_2d_N = Vec2D(0.0,0.0)

        self.impulse_2d_Ns = Vec2D(0.0,0.0)
        
        self.selected = False
        
        self.color = puck_color
        
        self.client_name = None
        self.jet = None
        self.gun = None
        self.hit = False
        
        # Bullet data...
        self.bullet = False
        self.birth_time_s = env.time_s
        self.age_limit_s = 3.0
        
        
    # If you print an object instance...
    def __str__(self):
        return "puck: x is %s, y is %s" % (self.pos_2d_m.x, self.pos_2d_m.y)
        
    def draw(self):
        # Convert x,y to pixel screen location and then draw.
        
        self.pos_2d_px = env.ConvertWorldToScreen( self.pos_2d_m)
        #print "draw position", self.pos_px[0], self.pos_px[1]
        
        # Update based on zoom factor
        self.radius_px = int(round(env.px_from_m( self.radius_m)))
        if (self.radius_px < 3):
            self.radius_px = 3
            
        # Just after a hit, fill the whole circle with RED (i.e., thickness = 0).
        if self.hit:
            puck_circle_thickness = 0
            puck_color = THECOLORS["red"]
            self.hit = False
        else:
            puck_circle_thickness = 3
            puck_color = self.color
        
        # Draw main puck body.
        pygame.draw.circle(game_window.surface, puck_color, self.pos_2d_px, self.radius_px, puck_circle_thickness)
        
        
        # Draw life (poor health) indicator circle.
        if (self.client_name != None) and (not self.bullet):
            spent_fraction = float(env.clients[self.client_name].bullet_hit_count) / float(env.clients[self.client_name].bullet_hit_limit)
            life_radius = spent_fraction * self.radius_px
            if (life_radius > 2.0):
                life_radius_px = int(round(life_radius))
            else:
                life_radius_px = 2
            
            
            pygame.draw.circle(game_window.surface, THECOLORS["red"], self.pos_2d_px, life_radius_px, 1)

            
class RotatingTube:
    def __init__(self, tube_base_2d_m):
        self.color = THECOLORS["yellow"]
        
        # Degrees of rotation per rendering cycle.
        self.rotation_deg = 1.8
        
        # Scaling factors to manage the aspect ratio of the tube.
        self.sf_x = 0.15
        self.sf_y = 0.50
        
        self.tube_base_2d_m = tube_base_2d_m
        
        # Notice the counter-clockwise drawing pattern. Four vertices for a rectangle.
        # Each vertex is represented by a vector.
        self.tube_vertices_2d_m = [Vec2D(-0.50 * self.sf_x, 0.00 * self.sf_y), 
                                   Vec2D( 0.50 * self.sf_x, 0.00 * self.sf_y), 
                                   Vec2D( 0.50 * self.sf_x, 1.00 * self.sf_y),
                                   Vec2D(-0.50 * self.sf_x, 1.00 * self.sf_y)]
        
        # Define a normal (1 meter) pointing vector to keep track of the direction of the jet.
        self.direction_2d_m = Vec2D(0.0, 1.0)
        
    def rotate_vertices(self, vertices_2d_m, angle_deg):
        # Put modified vectors in a new list.
        rotated_vertices_2d_m = []
        for vertex_2d_m in vertices_2d_m:
            rotated_vertices_2d_m.append( vertex_2d_m.rotated( angle_deg))
        return rotated_vertices_2d_m
    
    def rotate_everything(self, angle_deg):
        # Rotate the pointer.
        self.direction_2d_m = self.direction_2d_m.rotated( angle_deg)
        
        # Rotate the tube.
        self.tube_vertices_2d_m = self.rotate_vertices( self.tube_vertices_2d_m, angle_deg)
        
    def client_rotation_control(self, client_name):
        # Rotate clockwise (D) and counter-clockwise (A).
        if (env.clients[client_name].key_a == "D"):
            self.rotate_everything( +1 * self.rotation_deg)
        if (env.clients[client_name].key_d == "D"):
            self.rotate_everything( -1 * self.rotation_deg)
            
    def convert_from_world_to_screen(self, vertices_2d_m, base_point_2d_m):
        vertices_2d_px = []
        for vertex_2d_m in vertices_2d_m:
            # Calculate absolute position of this vertice.
            vertices_2d_px.append( env.ConvertWorldToScreen( vertex_2d_m + base_point_2d_m))
        return vertices_2d_px
        
    def draw(self):
        # Draw the tube on the game-window surface.
        pygame.draw.polygon(game_window.surface, self.color, 
                            self.convert_from_world_to_screen(self.tube_vertices_2d_m, self.tube_base_2d_m), 3)


class Spring:
    def __init__(self, p1, p2, length_m=3.0, strength_Npm=0.5, spring_color=THECOLORS["yellow"], width_m=0.025):
        self.p1 = p1
        self.p2 = p2
        self.p1p2_separation_2d_m = Vec2D(0,0)
        self.p1p2_separation_m = 0
        self.p1p2_normalized_2d = Vec2D(0,0)
        
        self.length_m = length_m
        self.strength_Npm = strength_Npm
        self.damper_Ns2pm2 = 0.5 #5.0 #0.05 #0.15
        self.unstretched_width_m = width_m #0.05
        
        self.spring_vertices_2d_m = []
        self.spring_vertices_2d_px = []
        
        self.spring_color = spring_color
        self.draw_as_line = False
        
    
    def calc_spring_forces_on_pucks(self):
        self.p1p2_separation_2d_m = self.p1.pos_2d_m - self.p2.pos_2d_m
        
        self.p1p2_separation_m =  self.p1p2_separation_2d_m.length()
        
        self.p1p2_normalized_2d = self.p1p2_separation_2d_m / self.p1p2_separation_m
        
        # Spring force:  acts along the separation vector and is proportional to the seperation distance.
        spring_force_on_1_N = self.p1p2_normalized_2d * (self.length_m - self.p1p2_separation_m) * self.strength_Npm
        
        # Damper force:  acts along the separation vector and is proportional to the relative speed.
        v_relative_2d_mps = self.p1.vel_2d_mps - self.p2.vel_2d_mps
        v_relative_alongNormal_2d_mps = v_relative_2d_mps.projection_onto(self.p1p2_normalized_2d)
        damper_force_on_1_N = v_relative_alongNormal_2d_mps * self.damper_Ns2pm2
        
        # Net force by both spring and damper
        SprDamp_force_2d_N = spring_force_on_1_N - damper_force_on_1_N
        
        # This force acts in opposite directions for each of the two pucks. Notice the "+=" here, this
        # is an aggregate across all the springs. This aggregate MUST be reset (zeroed) after the movements are
        # calculated. So by the time you've looped through all the springs, you get the NET force, one each ball, 
        # applied of all individual springs.
        self.p1.SprDamp_force_2d_N += SprDamp_force_2d_N * (+1) 
        self.p2.SprDamp_force_2d_N += SprDamp_force_2d_N * (-1)
        
        # This would be an alternate way to handle this. Directly calculate the effect on puck velocities.
        # Apply the spring and damper force in changing the velocity of the two pucks.
        # self.p1.vel_2d_mps = self.p1.vel_2d_mps + (self.p1.SprDamp_force_2d_N * (dt_physics_s/self.p1.mass_kg))
        # self.p2.vel_2d_mps = self.p2.vel_2d_mps + (self.p2.SprDamp_force_2d_N * (dt_physics_s/self.p2.mass_kg))
    
    def width_to_draw_m(self):
        width_m = self.unstretched_width_m * (1 + 0.30 * (self.length_m - self.p1p2_separation_m))
        if width_m < (0.05 * self.unstretched_width_m):
            self.draw_as_line = True
            width_m = 0.0
        else:
            self.draw_as_line = False
        return width_m
    
    def draw(self):   
        # Change the width to indicate the stretch or compression in the spring. Note, it's good to 
        # do this outside of the main calc loop (using the redering timer). No need to do all this each
        # time step.
        
        width_m = self.width_to_draw_m()
        
        # Calculate the four corners of the spring rectangle.
        p1p2_perpendicular_2d = self.p1p2_normalized_2d.rotate90()
        self.spring_vertices_2d_m = []
        self.spring_vertices_2d_m.append(self.p1.pos_2d_m + (p1p2_perpendicular_2d * width_m))
        self.spring_vertices_2d_m.append(self.p1.pos_2d_m - (p1p2_perpendicular_2d * width_m))
        self.spring_vertices_2d_m.append(self.p2.pos_2d_m - (p1p2_perpendicular_2d * width_m))
        self.spring_vertices_2d_m.append(self.p2.pos_2d_m + (p1p2_perpendicular_2d * width_m))
        
        # Transform from world to screen.
        self.spring_vertices_2d_px = []
        for vertex_2d_m in self.spring_vertices_2d_m:
            self.spring_vertices_2d_px.append( env.ConvertWorldToScreen( vertex_2d_m))
        
        # Draw the spring
        if self.draw_as_line == True:
            pygame.draw.aaline(game_window.surface, self.spring_color, env.ConvertWorldToScreen(self.p1.pos_2d_m),
                                                                       env.ConvertWorldToScreen(self.p2.pos_2d_m))
        else:
            pygame.draw.polygon(game_window.surface, self.spring_color, self.spring_vertices_2d_px)
        
class AirTable:
    def __init__(self, walls_dic):
        self.gON_mps2 = Vec2D(-0.0, -9.0)
        self.gOFF_mps2 = Vec2D(-0.0, -0.0)
        self.g_2d_mps2 = self.gOFF_mps2
        self.g_ON = False
        
        self.pucks = []
        self.controlled_pucks = []
        self.springs = []
        self.walls = walls_dic
        
        self.tubes = []
        
        self.collision_count = 0
        self.coef_rest_puck =  0.90
        self.coef_rest_table = 0.90
        
        self.color_transfer = False
                             
    def draw(self):
        #{"L_m":0.0, "R_m":10.0, "B_m":0.0, "T_m":10.0}
        topLeft_2d_px =   env.ConvertWorldToScreen( Vec2D( self.walls['L_m'],        self.walls['T_m']))
        topRight_2d_px =  env.ConvertWorldToScreen( Vec2D( self.walls['R_m']-0.01,   self.walls['T_m']))
        botLeft_2d_px =   env.ConvertWorldToScreen( Vec2D( self.walls['L_m'],        self.walls['B_m']+0.01))
        botRight_2d_px =  env.ConvertWorldToScreen( Vec2D( self.walls['R_m']-0.01,   self.walls['B_m']+0.01))
        
        pygame.draw.line(game_window.surface, THECOLORS["orangered1"], topLeft_2d_px,  topRight_2d_px, 1)
        pygame.draw.line(game_window.surface, THECOLORS["orangered1"], topRight_2d_px, botRight_2d_px, 1)
        pygame.draw.line(game_window.surface, THECOLORS["orangered1"], botRight_2d_px, botLeft_2d_px,  1)
        pygame.draw.line(game_window.surface, THECOLORS["orangered1"], botLeft_2d_px,  topLeft_2d_px,  1)
    
    def checkForPuckAtThisPosition(self, x_px_or_tuple, y_px = None):
        if y_px == None:
            self.x_px = x_px_or_tuple[0]
            self.y_px = x_px_or_tuple[1]
        else:
            self.x_px = x_px_or_tuple
            self.y_px = y_px
        
        test_position_m = env.ConvertScreenToWorld(Vec2D(self.x_px, self.y_px))
        for puck in self.pucks:
            vector_difference_m = test_position_m - puck.pos_2d_m
            # Use squared lengths for speed (avoid square root)
            mag_of_difference_m2 = vector_difference_m.length_squared()
            if mag_of_difference_m2 < puck.radius_m**2:
                puck.selected = True
                return puck
        return None

    def update_PuckSpeedAndPosition(self, puck, dt_s):
        # Net resulting force on the puck.
        puck_forces_2d_N = (self.g_2d_mps2 * puck.mass_kg) + (puck.SprDamp_force_2d_N + 
                                                              puck.jet_force_2d_N +
                                                              puck.cursorString_spring_force_2d_N +
                                                              puck.cursorString_puckDrag_force_2d_N +
                                                              puck.impulse_2d_Ns/dt_s)
        
        # Acceleration from Newton's law.
        acc_2d_mps2 = puck_forces_2d_N / puck.mass_kg
        
        # Acceleration changes the velocity:  dv = a * dt
        # Velocity at the end of the timestep.
        puck.vel_2d_mps = puck.vel_2d_mps + (acc_2d_mps2 * dt_s)
        
        # Calculate the new physical puck position using the average velocity.
        # Velocity changes the position:  dx = v * dt
        puck.pos_2d_m = puck.pos_2d_m + (puck.vel_2d_mps * dt_s)
        
        # Now reset the aggregate forces.
        puck.SprDamp_force_2d_N = Vec2D(0.0,0.0)
        puck.cursorString_spring_force_2d_N = Vec2D(0.0,0.0)
        puck.cursorString_puckDrag_force_2d_N = Vec2D(0.0,0.0)
        puck.impulse_2d_Ns = Vec2D(0.0,0.0)
    
    def check_for_collisions(self):
        correct_for_wall_penetration = True
        correct_for_puck_penetration = True
        
        for i, puck in enumerate(self.pucks):
            if (((puck.pos_2d_m.y - puck.radius_m) < self.walls["B_m"]) or ((puck.pos_2d_m.y + puck.radius_m) > self.walls["T_m"])):
                
                if correct_for_wall_penetration:
                    if (puck.pos_2d_m.y - puck.radius_m) < self.walls["B_m"]:
                        penetration_y_m = self.walls["B_m"] - (puck.pos_2d_m.y - puck.radius_m)
                        puck.pos_2d_m.y += 2 * penetration_y_m
                
                    if (puck.pos_2d_m.y + puck.radius_m) > self.walls["T_m"]:
                        penetration_y_m = (puck.pos_2d_m.y + puck.radius_m) - self.walls["T_m"]
                        puck.pos_2d_m.y -= 2 * penetration_y_m
                
                puck.vel_2d_mps.y *= -1 * self.coef_rest_table
            
            if (((puck.pos_2d_m.x - puck.radius_m) < self.walls["L_m"]) or ((puck.pos_2d_m.x + puck.radius_m) > self.walls["R_m"])):
                
                if correct_for_wall_penetration:
                    if (puck.pos_2d_m.x - puck.radius_m) < self.walls["L_m"]:
                        penetration_x_m = self.walls["L_m"] - (puck.pos_2d_m.x - puck.radius_m)
                        puck.pos_2d_m.x += 2 * penetration_x_m
                
                    if (puck.pos_2d_m.x + puck.radius_m) > self.walls["R_m"]:
                        penetration_x_m = (puck.pos_2d_m.x + puck.radius_m) - self.walls["R_m"]
                        puck.pos_2d_m.x -= 2 * penetration_x_m
                        
                puck.vel_2d_mps.x *= -1 * self.coef_rest_table
                
            # Collisions with other pucks. 
            for otherpuck in self.pucks[i+1:]:
                
                # Check if the two puck circles are overlapping.
                
                # Parallel to the normal
                puck_to_puck_2d_m = otherpuck.pos_2d_m - puck.pos_2d_m
                # Parallel to the tangent
                tanget_p_to_p_2d_m = Vec2D.rotate90(puck_to_puck_2d_m)
                
                p_to_p_m2 = puck_to_puck_2d_m.length_squared()
                
                # Keep this check fast by avoiding square roots.
                if (p_to_p_m2 < (puck.radius_m + otherpuck.radius_m)**2):
                    self.collision_count += 1
                    #print "collision_count", self.collision_count
                    
                    # If it's a bullet coming from another client, add to the
                    # hit count for non-bullet client.
                    if (puck.client_name != None) and (otherpuck.client_name != None):
                        if (puck.client_name != otherpuck.client_name): 
                            if (otherpuck.bullet and (not puck.bullet)):
                                if not puck.gun.shield:
                                    env.clients[puck.client_name].bullet_hit_count += 1
                                    puck.hit = True
                                else:
                                    puck.gun.shield_hit_count += 1
                    
                    if self.color_transfer == True:
                        #(puck.color, otherpuck.color) = (otherpuck.color, puck.color)
                        pass
                    
                    # Use the p_to_p vector (between the two colliding pucks) as projection target for 
                    # normal calculation.
                    
                    # The calculate velocity components along and perpendicular to the normal.
                    puck_normal_2d_mps = puck.vel_2d_mps.projection_onto(puck_to_puck_2d_m)
                    puck_tangent_2d_mps = puck.vel_2d_mps.projection_onto(tanget_p_to_p_2d_m)
                    
                    otherpuck_normal_2d_mps = otherpuck.vel_2d_mps.projection_onto(puck_to_puck_2d_m)
                    otherpuck_tangent_2d_mps = otherpuck.vel_2d_mps.projection_onto(tanget_p_to_p_2d_m)
                    
                    relative_normal_vel_2d_mps = otherpuck_normal_2d_mps - puck_normal_2d_mps
                    
                    if correct_for_puck_penetration:
                        # Back out a total of 2x of the penetration along the normal. Back-out amounts for each puck is 
                        # based on the velocity of each puck time 2DT where DT is the time of penetration. DT is calculated
                        # from the relative speed and the penetration distance.
                        
                        relative_normal_spd_mps = relative_normal_vel_2d_mps.length()
                        penetration_m = (puck.radius_m + otherpuck.radius_m) - p_to_p_m2**0.5
                        if (relative_normal_spd_mps > 0.00001):
                            penetration_time_s = penetration_m / relative_normal_spd_mps
                            
                            penetration_time_scaler = 1.0  # This can be useful for testing to amplify and see the correction.
                            
                            # First, reverse the two pucks, to their collision point, along their incoming trajectory paths.
                            puck.pos_2d_m = puck.pos_2d_m - (puck_normal_2d_mps * (penetration_time_scaler * penetration_time_s))
                            otherpuck.pos_2d_m = otherpuck.pos_2d_m - (otherpuck_normal_2d_mps * (penetration_time_scaler * penetration_time_s))
                            
                            # Calculate the velocities along the normal AFTER the collision. Use a CR (coefficient of restituion)
                            # of 1 here to better avoid stickiness.
                            CR_puck = 1
                            puck_normal_AFTER_mps, otherpuck_normal_AFTER_mps = self.AandB_normal_AFTER_2d_mps( puck_normal_2d_mps, puck.mass_kg, otherpuck_normal_2d_mps, otherpuck.mass_kg, CR_puck)
                                                           
                            # Finally, travel another penetration time worth of distance using these AFTER-collision velocities.
                            # This will put the pucks where they should have been at the time of collision detection.
                            puck.pos_2d_m = puck.pos_2d_m + (puck_normal_AFTER_mps * (penetration_time_scaler * penetration_time_s))
                            otherpuck.pos_2d_m = otherpuck.pos_2d_m + (otherpuck_normal_AFTER_mps * (penetration_time_scaler * penetration_time_s))
                            
                        else:
                            pass
                            #print "small relative speed"
                            #self.g_2d_mps2 = self.gOFF_mps2
                            # for puck in self.pucks:
                                # puck.vel_2d_mps = Vec2D(0,0)
                           
                    # Assign the AFTER velocities (using the actual CR here) to the puck for use in the next frame calculation.
                    CR_puck = self.coef_rest_puck
                    puck_normal_AFTER_mps, otherpuck_normal_AFTER_mps = self.AandB_normal_AFTER_2d_mps( puck_normal_2d_mps, puck.mass_kg, otherpuck_normal_2d_mps, otherpuck.mass_kg, CR_puck)
                    
                    # Now that we're done using the current values, set them to the newly calculated AFTERs.
                    puck_normal_2d_mps, otherpuck_normal_2d_mps = puck_normal_AFTER_mps, otherpuck_normal_AFTER_mps
                                        
                    # Add the components back together to get total velocity vectors for each puck.
                    puck.vel_2d_mps = puck_normal_2d_mps + puck_tangent_2d_mps
                    otherpuck.vel_2d_mps = otherpuck_normal_2d_mps + otherpuck_tangent_2d_mps
    
    def normal_AFTER_2d_mps(self, A_normal_BEFORE_2d_mps, A_mass_kg, B_normal_BEFORE_2d_mps, B_mass_kg, CR_puck):
        # For inputs as defined here, this returns the AFTER normal for the first puck in the inputs. So if B
        # is first, it returns the result for the B puck.
        relative_normal_vel_2d_mps = B_normal_BEFORE_2d_mps - A_normal_BEFORE_2d_mps
        return ( ( (relative_normal_vel_2d_mps * (CR_puck * B_mass_kg)) + 
                   (A_normal_BEFORE_2d_mps * A_mass_kg + B_normal_BEFORE_2d_mps * B_mass_kg) ) /
                   (A_mass_kg + B_mass_kg) ) 
    
    def AandB_normal_AFTER_2d_mps(self, A_normal_BEFORE_2d_mps, A_mass_kg, B_normal_BEFORE_2d_mps, B_mass_kg, CR_puck):
        A = self.normal_AFTER_2d_mps(A_normal_BEFORE_2d_mps, A_mass_kg, B_normal_BEFORE_2d_mps, B_mass_kg, CR_puck)
        # Make use of the symmetry in the physics to calculate the B normal (put the B data in the first inputs).
        B = self.normal_AFTER_2d_mps(B_normal_BEFORE_2d_mps, B_mass_kg, A_normal_BEFORE_2d_mps, A_mass_kg, CR_puck)
        return A, B
    

class Environment:
    def __init__(self, screenSize_px, length_x_m):
        self.screenSize_px = Vec2D(screenSize_px)
        self.viewOffset_px = Vec2D(0,0)
        self.viewCenter_px = Vec2D(0,0)
        self.viewZoom = 1
        self.viewZoom_rate = 0.01
    
        self.px_to_m = length_x_m/float(self.screenSize_px.x)
        self.m_to_px = (float(self.screenSize_px.x)/length_x_m)
        
        self.client_colors = {'C1': THECOLORS["orangered1"],'C2': THECOLORS["tan"],'C3': THECOLORS["cyan"],'C4': THECOLORS["blue"],
                              'C5': THECOLORS["pink"], 'C6': THECOLORS["red"],'C7': THECOLORS["coral"],'C8': THECOLORS["green"],
                              'C9': THECOLORS["grey80"],'C10': THECOLORS["rosybrown3"]}
                              
        # Add a local (non-network) client to the client dictionary.
        self.clients = {'local':Client(THECOLORS["green"])}
        
        self.time_s = 0
                              
    def remove_healthless_clients(self):
        # Make a list of terminal clients.
        #print len(air_table.pucks), len(air_table.controlled_pucks)
        
        spent_client_names = []
        for thisclient_name in self.clients:
            if self.clients[thisclient_name].bullet_hit_count > self.clients[thisclient_name].bullet_hit_limit:
                spent_client_names.append( thisclient_name)
                # Reset so don't keep trying to delete it.
                #self.clients[thisclient_name].bullet_hit_count = 0
        
        pucks_list_copy = air_table.pucks[:]
        for puck in pucks_list_copy:
            if puck.client_name in spent_client_names:
                # Had to put this check in to prevent server crash on simultaneous death bullets between two clients.
                # Don't yet understand why this is necessary.
                if (puck in air_table.controlled_pucks):
                    air_table.controlled_pucks.remove( puck)
                else:
                    print puck.client_name, "puck not in the controlled puck list."
                air_table.pucks.remove( puck)
        
        for spent_client in spent_client_names:
            # Remove client from client dictionary
            if (spent_client != 'local'):
                del self.clients[ spent_client]
              
        del pucks_list_copy
    
    # Convert from meters to pixels 
    def px_from_m(self, dx_m):
        return dx_m * self.m_to_px * self.viewZoom
    
    # Convert from pixels to meters
    # Note: still floating values here)
    def m_from_px(self, dx_px):
        return float(dx_px) * self.px_to_m / self.viewZoom
    
    def control_zoom_and_view(self):
        if self.clients['local'].key_h == "D":
            self.viewZoom += self.viewZoom_rate * self.viewZoom
        if self.clients['local'].key_n == "D":
            self.viewZoom -= self.viewZoom_rate * self.viewZoom
    
    def ConvertScreenToWorld(self, point_2d_px):
        #self.viewOffset_px = self.viewCenter_px
        x_m = (                       point_2d_px.x + self.viewOffset_px.x) / (self.m_to_px * self.viewZoom)
        y_m = (self.screenSize_px.y - point_2d_px.y + self.viewOffset_px.y) / (self.m_to_px * self.viewZoom)
        return Vec2D( x_m, y_m)

    def ConvertWorldToScreen(self, point_2d_m):
        """
        Convert from world to screen coordinates (pixels).
        In the class instance, we store a zoom factor, an offset indicating where
        the view extents start at, and the screen size (in pixels).
        """

        # self.viewOffset = self.viewCenter - self.screenSize_px/2
        #self.viewOffset = self.viewCenter_px
        x_px = (point_2d_m.x * self.m_to_px * self.viewZoom) - self.viewOffset_px.x
        y_px = (point_2d_m.y * self.m_to_px * self.viewZoom) - self.viewOffset_px.y
        y_px = self.screenSize_px.y - y_px

        # Return a tuple of integers.
        return Vec2D(x_px, y_px, "int").tuple()

    def get_local_user_input(self):
        local_user = self.clients['local']
        
        # Get all the events since the last call to get().
        for event in pygame.event.get():
            if (event.type == pygame.QUIT): 
                sys.exit()
            elif (event.type == pygame.KEYDOWN):
                if (event.key == K_ESCAPE):
                    sys.exit()
                elif (event.key==K_1):            
                    return 1           
                elif (event.key==K_2):                          
                    return 2
                elif (event.key==K_3):
                    return 3           
                elif (event.key==K_4):
                    return 4           
                elif (event.key==K_5):
                    return 5
                elif (event.key==K_6):
                    return 6
                elif (event.key==K_7):
                    return 7
                elif (event.key==K_8):
                    return 8
                elif (event.key==K_9):
                    return 9
                elif (event.key==K_0):
                    return 0
                
                elif (event.key==K_c):
                    # Toggle color option.
                    air_table.color_transfer = not air_table.color_transfer
                    #form['ColorTransfer'].value = air_table.color_transfer
                
                elif (event.key==K_f):
                    for puck in air_table.pucks:
                        puck.vel_2d_mps = Vec2D(0,0)
                
                elif (event.key==K_g):
                    if air_table.g_ON:
                        air_table.g_2d_mps2 = air_table.gOFF_mps2
                        air_table.coef_rest_puck =  1.00
                        air_table.coef_rest_table =  1.00
                    else:
                        air_table.g_2d_mps2 = air_table.gON_mps2
                        air_table.coef_rest_puck =  0.90
                        air_table.coef_rest_table =  0.90
                    air_table.g_ON = not air_table.g_ON
                    print "g", air_table.g_ON
                
                elif (event.key==K_F2):
                    # Toggle menu on/off
                    #air_table.gui_menu = not air_table.gui_menu
                    pass
                
                # Jet keys
                elif (event.key==K_a):
                    local_user.key_a = 'D'
                elif (event.key==K_s):
                    local_user.key_s = 'D'
                elif (event.key==K_d):
                    local_user.key_d = 'D'
                elif (event.key==K_w):
                    local_user.key_w = 'D'
                
                # Gun keys
                elif (event.key==K_j):
                    local_user.key_j = 'D'
                elif (event.key==K_k):
                    local_user.key_k = 'D'
                elif (event.key==K_l):
                    local_user.key_l = 'D'
                elif (event.key==K_i):
                    local_user.key_i = 'D'
                elif (event.key==K_SPACE):
                    local_user.key_space = 'D'
                    
                # Zoom keys
                elif (event.key==K_b):
                    local_user.key_b = 'D'
                elif (event.key==K_n):
                    local_user.key_n = 'D'
                elif (event.key==K_m):
                    local_user.m = 'D'
                elif (event.key==K_h):
                    local_user.key_h = 'D'
                
                else:
                    return "nothing set up for this key"
            
            elif (event.type == pygame.KEYUP):
                # Jet keys
                if   (event.key==K_a):
                    local_user.key_a = 'U'
                elif (event.key==K_s):
                    local_user.key_s = 'U'
                elif (event.key==K_d):
                    local_user.key_d = 'U'
                elif (event.key==K_w):
                    local_user.key_w = 'U'
                
                # Gun keys
                elif (event.key==K_j):
                    local_user.key_j = 'U'
                elif (event.key==K_k):
                    local_user.key_k = 'U'
                elif (event.key==K_l):
                    local_user.key_l = 'U'
                elif (event.key==K_i):
                    local_user.key_i = 'U'
                elif (event.key==K_SPACE):
                    local_user.key_space = 'U'
                    
                # Zoom keys
                elif (event.key==K_b):
                    local_user.key_b = 'U'
                elif (event.key==K_n):
                    local_user.key_n = 'U'
                elif (event.key==K_m):
                    local_user.key_m = 'U'
                elif (event.key==K_h):
                    local_user.key_h = 'U'
            
            elif event.type == pygame.MOUSEBUTTONDOWN:
                local_user.buttonIsStillDown = True
            
                (button1, button2, button3) = pygame.mouse.get_pressed()
                if button1:
                    local_user.mouse_button = 1
                elif button2:
                    local_user.mouse_button = 2
                elif button3:
                    local_user.mouse_button = 3
                else:
                    local_user.mouse_button = 0
            
            elif event.type == pygame.MOUSEBUTTONUP:
                local_user.buttonIsStillDown = False
                local_user.mouse_button = 0
            
            # In all cases, pass the event to the Gui.
            #app.event(event)
        
        if local_user.buttonIsStillDown:
            # This will select a puck when the puck runs into the cursor of the mouse with it's button still down.
            local_user.cursor_location_px = (mouseX, mouseY) = pygame.mouse.get_pos()

            # Only check for a selected puck if one isn't already selected. This keeps
            # the puck from unselecting if cursor is dragged off the puck!
            # if not local_user.selected_puck:
                # # Effectively waits for a puck to run over the cursor.
                # local_user.selected_puck = air_table.checkForPuckAtThisPosition(mouseX, mouseY)

        
class GameWindow:
    def __init__(self, screen_tuple_px, title):
        self.width_px = screen_tuple_px[0]
        self.height_px = screen_tuple_px[1]
        
        # The initial World position vector of the Upper Right corner of the screen.
        # Yes, that's right y_px = 0 for UR.
        self.UR_2d_m = env.ConvertScreenToWorld(Vec2D(self.width_px, 0))
        
        # Create a reference to the display surface object. This is a pygame "surface".
        # Screen dimensions in pixels (tuple)
        self.surface = pygame.display.set_mode(screen_tuple_px)

        self.update_caption(title)
        
        self.surface.fill(THECOLORS["black"])
        pygame.display.update()
        
    def update_caption(self, title):
        pygame.display.set_caption( title)
        self.caption = title
    
    def update(self):
        pygame.display.update()
        
    def clear(self):
        # Useful for shifting between the various demos.
        self.surface.fill(THECOLORS["black"])
        pygame.display.update()

#===========================================================
# Functions
#===========================================================
        
def make_some_pucks(resetmode):
    game_window.update_caption("Air Table V.2: Demo #" + str(resetmode)) 
    
    if resetmode == 1:
        #                                              ,radius,density
        air_table.pucks.append( Puck(Vec2D(2.5, 7.5), 0.25, 0.3, THECOLORS["orange"]))
        air_table.pucks.append( Puck(Vec2D(6.0, 2.5), 0.45, 0.3)) # maybe not.
        air_table.pucks.append( Puck(Vec2D(7.5, 2.5), 0.65, 0.3)) 
        air_table.pucks.append( Puck(Vec2D(2.5, 5.5), 1.65, 0.3))
        air_table.pucks.append( Puck(Vec2D(7.5, 7.5), 0.95, 0.3))
    
    elif resetmode == 4:
        #air_table.gON_mps2 = Vec2D(-0.0, -20.0)
        spacing_factor = 1.0
        grid_size = 9,6   #9,6
        for j in range(grid_size[0]):
            for k in range(grid_size[1]):
                if ((j,k) == (2,2)):
                    air_table.pucks.append( Puck(Vec2D(spacing_factor*(j+1), spacing_factor*(k+1)), 0.25, 5.0, THECOLORS["orange"]))
                else:
                    air_table.pucks.append( Puck(Vec2D(spacing_factor*(j+1), spacing_factor*(k+1)), 0.25, 5.0))
        #Nudge the first puck a little
        #air_table.pucks[53].pos_2d_m = air_table.pucks[53].pos_2d_m + Vec2D(0.00001 , 0.0)
        #air_table.pucks[3].pos_2d_m = air_table.pucks[3].pos_2d_m + Vec2D(0.00001 , 0.0)
    
    elif resetmode == 3:
        spacing_factor = 1.5
        grid_size = 5,3
        for j in range(grid_size[0]):
            for k in range(grid_size[1]):                
                if ((j,k) == (2,2)):
                    air_table.pucks.append( Puck(Vec2D(spacing_factor*(j+1), spacing_factor*(k+1)), 0.55, 0.3, THECOLORS["orange"]))
                else:    
                    air_table.pucks.append( Puck(Vec2D(spacing_factor*(j+1), spacing_factor*(k+1)), 0.55, 0.3))
    
    elif resetmode == 2:
        spacing_factor = 2.0
        grid_size = 4,2
        for j in range(grid_size[0]):
            for k in range(grid_size[1]):
                if ((j,k) == (1,1)):
                    air_table.pucks.append( Puck(Vec2D(spacing_factor*(j+1), spacing_factor*(k+1)), 0.75, 0.3, THECOLORS["orange"]))
                else:    
                    air_table.pucks.append( Puck(Vec2D(spacing_factor*(j+1), spacing_factor*(k+1)), 0.75, 0.3))
    
    elif resetmode == 6:
        air_table.pucks.append( Puck(Vec2D(2.00, 3.00),  0.65, 0.3) )
        air_table.pucks.append( Puck(Vec2D(3.50, 4.50),  0.65, 0.3) )
        air_table.pucks.append( Puck(Vec2D(5.00, 3.00),  0.65, 0.3) )
        
        # No springs on this one.
        air_table.pucks.append( Puck(Vec2D(3.50, 7.00),  0.95, 0.3) )
    
        spring_strength_Npm2 = 200.0 #18.0
        spring_length_m = 2.5
        spring_width_m = 0.07
        air_table.springs.append( Spring(air_table.pucks[0], air_table.pucks[1],
                                         spring_length_m, spring_strength_Npm2, width_m=spring_width_m))
        air_table.springs.append( Spring(air_table.pucks[1], air_table.pucks[2],
                                         spring_length_m, spring_strength_Npm2, width_m=spring_width_m))
        air_table.springs.append( Spring(air_table.pucks[2], air_table.pucks[0],
                                         spring_length_m, spring_strength_Npm2, width_m=spring_width_m))
    
    elif resetmode == 5:
        air_table.pucks.append( Puck(Vec2D(2.00, 3.00),  0.4, 0.3) )
        air_table.pucks.append( Puck(Vec2D(3.50, 4.50),  0.4, 0.3) )
        
        # No springs on this one.
        #air_table.pucks.append( Puck(Vec2D(3.50, 7.00),  0.95, 0.3) )
    
        spring_strength_Npm2 = 20.0 #18.0
        spring_length_m = 1.5
        air_table.springs.append( Spring(air_table.pucks[0], air_table.pucks[1], spring_length_m, spring_strength_Npm2, width_m=0.2))
    
    
    elif resetmode == 7:
        air_table.coef_rest_puck =  0.85
        air_table.coef_rest_table = 0.85
        
        # Make user/client controllable pucks
        # for all the clients.
        y_puck_position_m = 1.0
        for client_name in env.clients:
            tempPuck = Puck(Vec2D(6.0, y_puck_position_m), 0.45, 0.3)
            # Let the puck reference the jet and the jet reference the puck.
            tempPuck.client_name = client_name
            #tempPuck.jet = Jet( tempPuck)
            #tempPuck.gun = Gun( tempPuck)

            air_table.pucks.append( tempPuck)
            air_table.controlled_pucks.append( tempPuck)
            y_puck_position_m += 1.2
    
        air_table.tubes.append( RotatingTube( Vec2D(1.0, 1.0)))
        air_table.tubes.append( RotatingTube( Vec2D(2.0, 2.0)))
        air_table.tubes.append( RotatingTube( Vec2D(3.0, 3.0)))
    
    else:
        print "Nothing set up for this key."
        
#============================================================
# Main procedural script.
#============================================================

def main():

    # A few globals.
    global env, game_window, air_table
    
    pygame.init()

    myclock = pygame.time.Clock()

    window_dimensions_px = (800, 700)   #window_width_px, window_height_px

    # Create the first user/client and the methods for moving between the screen and the world.
    env = Environment(window_dimensions_px, 10.0) # 10m in along the x axis.

    game_window = GameWindow(window_dimensions_px, 'Air Table Server V.2')

    # Define the Left, Right, Bottom, and Top boundaries of the game window.
    air_table = AirTable({"L_m":0.0, "R_m":game_window.UR_2d_m.x, "B_m":0.0, "T_m":game_window.UR_2d_m.y})

    # Add some pucks to the table.
    make_some_pucks( 7)

    # Setup network server.
    local_ip = socket.gethostbyname(socket.gethostname())
    print "Server IP address:", local_ip
    game_server = GameServer(localaddr=(local_ip, 4330))

    # Font object for rendering text onto display surface.
    fnt = pygame.font.SysFont("Arial", 14)
    
    # Limit the framerate, but let it float below this limit.
    framerate_limit = 500
    dt_render_s = 0.0
    dt_render_limit_s = 1.0/120.0     # = 1.0/render_framerate

    qCount_limit = 100

    while True:
        dt_physics_s = float(myclock.tick( framerate_limit) * 1e-3)
        #dt_physics_s = 1/120.0
        #print dt_physics_s, myclock.get_fps()
        
        # This check avoids problem when dragging the game window.
        if (dt_physics_s < 0.10):
            
            # Get input from local user.
            resetmode = env.get_local_user_input()
            
            # Reset the game based on local user control.
            if resetmode in [0,1,2,3,4,5,6,7,8,9]:
                print resetmode
                # This should remove all references to the pucks and effectively kill them off. If there were other
                # variables refering to this list, this would not stop the pucks.
                
                # Delete all the objects on the table. Cleaning out these list reference to these objects effectively
                # deletes the objects. Notice the contolled list must be cleared also.
                air_table.pucks = []
                air_table.controlled_pucks = []
                air_table.springs = []
                air_table.tubes = []
                
                # Now just black out the screen.
                game_window.clear()
                
                # Reinitialize the demo.
                make_some_pucks( resetmode)               
                        
            if (dt_render_s > dt_render_limit_s):
                # Get input from network clients.
                game_server.Pump()
                
            for client_name in env.clients:
                # Calculate client related forces.
                env.clients[client_name].calc_string_forces_on_pucks()
                
            if (dt_render_s > dt_render_limit_s):
                # Control the zoom
                env.control_zoom_and_view()
                
                for controlled_puck in air_table.controlled_pucks:
                    # Rotate based on keyboard of the controlling client.
                    #controlled_puck.jet.rotate( controlled_puck.client_name)
                    #controlled_puck.gun.rotate( controlled_puck.client_name)
                    
                    
                    # Turn shield on/off
                    #controlled_puck.gun.control_shield( controlled_puck.client_name)
                    pass
                    
                for tube in air_table.tubes:
                    # Rotate based on keyboard of the controlling client.
                    tube.client_rotation_control('local')
                
            # Calculate jet forces on pucks...
            for controlled_puck in air_table.controlled_pucks:
                #controlled_puck.jet.turn_jet_forces_onoff( controlled_puck.client_name)
                pass
            
            # Calculate the forces the springs apply on the pucks...
            for eachspring in air_table.springs:
                eachspring.calc_spring_forces_on_pucks()
                
            # Apply forces to the pucks and calculate movements.
            for eachpuck in air_table.pucks:
                air_table.update_PuckSpeedAndPosition( eachpuck, dt_physics_s)
            
            # Check for puck-wall and puck-puck collisions and make penetration corrections.
            air_table.check_for_collisions()
            
            if (dt_render_s > dt_render_limit_s):
                
                # Erase the blackboard.
                game_window.surface.fill((0,0,0))

                # Small background rectangle for FPS text
                pygame.draw.rect(game_window.surface, THECOLORS["white"], pygame.Rect(10, 10, 35, 20))
                # The text
                fps_string = "%.0f" % myclock.get_fps()
                txt_surface = fnt.render(fps_string, True, THECOLORS["black"])
                game_window.surface.blit(txt_surface, [18, 11])
                
                # Clean out old bullets.
                puck_list_copy = air_table.pucks[:]
                for thisPuck in puck_list_copy:
                    if (thisPuck.bullet) and ((env.time_s - thisPuck.birth_time_s) > thisPuck.age_limit_s):
                        air_table.pucks.remove(thisPuck)
                del puck_list_copy       
                
                # Now draw pucks, springs, mouse tethers, and jets.
                
                # Draw boundaries of table.
                air_table.draw()
                
                for eachpuck in air_table.pucks: 
                    eachpuck.draw()
                    if (eachpuck.jet != None):
                        if ((env.clients[eachpuck.client_name].Qcount < qCount_limit) or (eachpuck.client_name == 'local')):
                            eachpuck.jet.draw()
                            #eachpuck.gun.draw()

                for eachtube in air_table.tubes:
                    eachtube.draw()
                
                for eachspring in air_table.springs: 
                    eachspring.draw()
                
                env.remove_healthless_clients()
                
                for client_name in env.clients:
                    if (env.clients[client_name].selected_puck != None):
                        env.clients[client_name].draw_cursor_string()
                    
                    # Draw cursors for network clients.
                    if ((client_name != 'local') and (env.clients[client_name].Qcount < qCount_limit)):
                        env.clients[client_name].draw_fancy_server_cursor()
                    
                pygame.display.flip()
                dt_render_s = 0
            
            # Limit the rendering framerate to be below that of the physics calculations.
            dt_render_s += dt_physics_s
            
            # Keep track of time for deleting old bullets.
            env.time_s += dt_physics_s

#============================================================
# Run the main program.    
#============================================================
        
main()