Attaaaack! python game

from random import *
import time, os, sys
def start(): # start script
    os.system('cls') # clears the screen for a fresh start
    art()
    def_health = 100 # can't be too high, or else errors will occur
    global health # globalise it for use outside of start()
    global player_name # globalise it for use outside of start()
    global p2_health # globalise it for use outside of start()
    global player2_name # globalise it for use outside of start()
    global turn # globalise it for use outside of start()
    global fast # globalise it for use outside of start()
    health = def_health # health is an integer
    p2_health = def_health # health is an integer
    player_name = 'Bot 1' # default players name
    player2_name = 'Bot 2' # default players name
    turn = randint(1,2) # determines randomly who begins
    fast = 0 # set to 1 for quick battles
    names = 1 # allows custom names, set to 0 for no
    if names == 1:
        player_name = raw_input('Player 1 name:>') # player 1 name
        player2_name = raw_input('Player 2 name:>') # player 2 name
    global first
    if turn == 1:
        first = player_name # player 1 goes first
    else:
        first = player2_name # player 2 goes first
    game() # call game()
def game(): #actual 'game' is here
    os.system('cls') # clears the screen for a fresh start
    art()
    print 'Players:'
    print '********'
    print "[1]", player_name, 'Health', health # player1 stats
    print "[2]", player2_name, 'Health', p2_health # player2 stats
    print '********'
    if turn == 1:
        nameshot = player_name
    else:                              # sets name of the next person to attack
        nameshot = player2_name
    print nameshot, 'will now attack.'
    if fast == 0:
        time.sleep(3) # waits 3 seconds before action
    attack() # now ataaack!
def attack():
    if turn == 1:
        minus = randint(5,30) # random amount of health loss
        global p2_health
        p2_health = p2_health - minus # set new health
        if p2_health < 1:
            p2_health = 0
            global winner
            winner = player_name
            end()
        global turn
        turn = 2 # selects next player as the next turn
        game() # return to game()
    else:
        minus = randint(5,30) # random amount of health loss
        global health
        health = health - minus # set new health
        if health < 1:
            health = 0
            global winner
            winner = player2_name
            end()
        global turn
        turn = 1 # selects next player as the next turn
        game() # return to game()
def end():
    os.system('cls') # clears the screen for a fresh start
    #print first, 'went first' # debugger
    art()
    print 'The winner is:', winner
    print 'Players:'
    print '********'
    print player_name, 'Health', health # player1 stats
    print player2_name, 'Health', p2_health # player2 stats
    print '********'
    sys.exit('Game Over')
def art(): # ATAAAAACK
    print '        _   _             _    _ '
    print '       | | | |           | |  | |'
    print '   __ _| |_| |_ __ _  ___| | _| |'
    print '  / _` | __| __/ _` |/ __| |/ / |'
    print ' | (_| | |_| || (_| | (__|   <|_|'
    print '  \__,_|\__|\__\__,_|\___|_|\_(_)'
    print ''
start() #starts the preperation function