Can someone add a map changer to this?

wait(1);
system = script.Parent
is_playing = system.Playing
stage = system.Stage
weapons = game.Workspace.Weapons
hum_team = game.Teams["Humans"]
zom_team = game.Teams["Zombies"]
msg = nil
hint = nil
playing = false
interrupted = false
minutes = 0
seconds = 0
function displayHint(text)
if(hint==nil)then
hint = Instance.new("Hint")
hint.Text = text
hint.Parent = game.Workspace
else
hint.Text = text
end
end
function removeHint()
if(hint~=nil)then hint:remove() hint = nil end
end
function displayMsg(text)
if(msg==nil)then
msg = Instance.new("Message")
msg.Text = text
msg.Parent = game.Workspace
else
msg.Text = text
end
end
function removeMsg()
if(msg~=nil)then msg:remove() msg = nil end
end
function giveWeapons()
local player = game.Players:GetChildren()
if(#player>0)then
for p = 1, #player do
if(player[p].TeamColor==hum_team.TeamColor)then
shared["Weps"]["Pistol"]:Clone().Parent = player[p].Backpack
end
end
end
end
function killPlayers()
local player = game.Players:GetChildren()
if(#player>0)then
for p = 1, #player do
if(player[p].Character~=nil)then
local h = player[p].Character:FindFirstChild("Humanoid")
if(h.Health>0)then
player[p].Character.Humanoid.Health = 0
else
if(player[p]:FindFirstChild("Dead")~=nil)then
player[p].Dead.Value = false
player[p].Class.Value = "Zombie"
player[p].TeamColor = hum_team.TeamColor
end
end
end
end
end
end
function resetPlayers()
local player = game.Players:GetChildren()
if(#player>0)then
for p = 1, #player do
if(player[p]:FindFirstChild("Dead")~=nil)then
player[p].Dead.Value = false
player[p].Class.Value = "Zombie"
player[p].TeamColor = hum_team.TeamColor
end
end
end
end
function countPlayers()
local count = 0
local player = game.Players:GetChildren()
if(#player>0)then
for p = 1, #player do
if(player[p].Character~=nil)then
count = count +1
end
end
end
return count
end
function countPlayersInTeam(team)
local team_count = 0
local player = game.Players:GetChildren()
if(#player>0)then
for p = 1, #player do
if(player[p].TeamColor==team.TeamColor)then
team_count = team_count +1
end
end
end
return team_count
end
function assignZombies(amount)
local valid_players = {}
local player = game.Players:GetChildren()
if(#player>0)then
for p = 1, #player do
if(player[p].TeamColor==hum_team.TeamColor)and
(player[p].Character~=nil)then
table.insert(valid_players,player[p])
end
end
end
if(#valid_players>amount)then
while(amount>0)do
local rand = math.random(1,#valid_players)
local chosen = valid_players[rand]
chosen.TeamColor = zom_team.TeamColor
chosen.Character.Humanoid.Health = 0

table.remove(valid_players,rand)
amount = amount -1
end
end
end

function countDown()
seconds = seconds -1
if(seconds<0)then
minutes = minutes -1
seconds = 59
if(minutes<0)then playing = false return true end
end

return false
end

function playZombies()
if(countPlayers()<=3)then
assignZombies(1)
elseif(countPlayers()<=6)then
assignZombies(2)
else
assignZombies(3)
end

is_playing.Value = true
Game.workspace.Unlocked:Play()
displayMsg("Human team, Fight the zombies for 15 minutes and avoid infection.")
wait(1);
for i,v in ipairs(game.Players:GetChildren()) do -- Should fix zombies not morphing.
if v.TeamColor == zom_team.TeamColor then
v.Character:BreakJoints();
end
end
delay(5,function () giveWeapons(); end); -- Wait for respawns?
delay(5,removeMsg)

interrupted = false
playing = true

	minutes = 12
	seconds = 59

	while(playing==true)and(countDown()==false)do
		local humans = countPlayersInTeam(hum_team)
		local zombies = countPlayersInTeam(zom_team)

		if(minutes==9)and(seconds==59)then
			stage.Value = 2
Game.workspace.Unlocked:Play()
			displayMsg("FAST zombie is NOW UNLOCKED! say '/fastzombie' to become a fast zombie!")
			delay(10,removeMsg)
		elseif(minutes==4)and(seconds==59)then
			stage.Value = 3
Game.workspace.Unlocked:Play()
			displayMsg("KamiZombie is NOW UNLOCKED! say '/kamizombie' to become a kamizombie!")
			delay(10,removeMsg)
		elseif(minutes==7)and(seconds==25)then
			stage.Value = 4
 Game.workspace.Unlocked:Play()
			displayMsg("Ghost ZOMBIE is NOW UNLOCKED! say '/ghostzombie' to become a Ghost!")
			delay(10,removeMsg)
		elseif(minutes==6)and(seconds==25)then
			stage.Value = 5
Game.workspace.Unlocked:Play()
			displayMsg("Fast GHOST Zombie is NOW UNLOCKED! say '/fastghostzombie' to become a FastGhostzombie!")
			delay(10,removeMsg)
		elseif(minutes==2)and(seconds==25)then
			stage.Value = 6
Game.workspace.Unlocked:Play()
			displayMsg("ZOMBIE BOSS is NOW UNLOCKED! say '/zombieboss' to become a BOSS!")
			delay(10,removeMsg)
		end

		if(seconds<10)then
			displayHint("Humans left: "..humans.." | Time left: "..minutes..":0"..seconds.." | Zombies: "..zombies)
		else
			displayHint("Humans left: "..humans.." | Time left: "..minutes..":"..seconds.." | Zombies: "..zombies)
		end

		if(zombies==0)then -- Zombies left the game? Try to assign another to keep the game running!
			if(countPlayers()>=2)then
				if(countPlayers()<=3)then
					assignZombies(1)
				elseif(countPlayers()<=6)then
					assignZombies(2)
				else
					assignZombies(3)
				end
			else
				interrupted = true
				break
			end
		end

		if(humans==0)then
			break
		end

		wait(1)
	end
	stage.Value = 1

	removeHint()

if(interrupted==true)then
Game.workspace.SENSATIONAL:Play()
displayMsg("There are not enough players to continue the game...")
else
if(playing==false)then
Game.workspace.SENSATIONAL:Play()
displayMsg("Humans have outlasted the zombies!")
else
Game.workspace.Rawr:Play()
displayMsg("Zombies have infected everyone!")
end
end

is_playing.Value = false

killPlayers()
wait(5)
resetPlayers()

removeMsg()
end

while true do
wait(3)
resetPlayers()
if(countPlayers()>=2)then
removeMsg()
playZombies()
else
displayMsg("There are not enough players to continue the game...")
end
end