Error "attempt to index field 'LocalPlayer' (a nil value)???

My game works perfectly in studio but it does not when published and played as a game. Can someone help please!

local ui = game.Players.LocalPlayer.PlayerGui
local c = 50
local v = 0
local sgui = Instance.new("ScreenGui")
sgui.Parent = ui
local textLabel = Instance.new("TextLabel")
textLabel.Parent = sgui
textLabel.Font = 12
textLabel.BackgroundColor3 = Color3.new(0,0.4,1)
textLabel.TextColor3 = Color3.new(0,0,0)
textLabel.BorderColor3 = Color3.new(0,0,0)
textLabel.BorderSizePixel = 4
textLabel.Text = "($"..c..") Amateur Swordsman(+1) Owned: 0"
textLabel.TextSize = 30
textLabel.Size = UDim2.new(.45,0,0,80)
textLabel.Position = UDim2.new(.275,0,0,100)
textLabel.Visible = false

local buyButton = Instance.new("TextButton")
buyButton.Parent = sgui
buyButton.Font = 12
buyButton.BackgroundColor3 = Color3.new(0,0,0)
buyButton.TextColor3 = Color3.new(1,1,1)
buyButton.BorderColor3 = Color3.new(1,1,1)
buyButton.BorderSizePixel = 4
buyButton.Text = "Purchase"
buyButton.TextSize = 30
buyButton.Size = UDim2.new(.1,0,0,35)
buyButton.Position = UDim2.new(.725,20,0,100)
buyButton.Visible = false

local Amount = Instance.new("TextBox")
Amount.Parent = sgui
Amount.Font = 12
Amount.BackgroundColor3 = Color3.new(0,0,0)
Amount.TextColor3 = Color3.new(1,1,1)
Amount.BorderColor3 = Color3.new(1,1,1)
Amount.BorderSizePixel = 4
Amount.Text = 1
Amount.TextSize = 30
Amount.Size = UDim2.new(.05,0,0,35)
Amount.Position = UDim2.new(.75,20,0,145)
Amount.Visible = false

function round(c)
	return math.floor(c+.5)
end

buyButton.MouseButton1Down:connect(function()
	local player = game.Players.LocalPlayer
	for _, player in pairs(game.Players:GetPlayers()) do
		if game.Players.LocalPlayer.leaderstats.Cash.Value >= c
			then game.Players.LocalPlayer.leaderstats.Cash.Value = game.Players.LocalPlayer.leaderstats.Cash.Value - c
	game.Workspace.Upgrade.UpgradeValue.Value = game.Workspace.Upgrade.UpgradeValue.Value + Amount.Text
	buyButton.Text = "Purchased"
	c = 50
	wait(.01)
	v = v + Amount.Text
	c = round(Amount.Text * c * 1.025^(v + Amount.Text) - 1)
	textLabel.Text = "($"..c..") Amateur Swordsman(Attack+1) Owned: ".. v
	wait(1)
	buyButton.Text = "Purchase"
		else
			buyButton.TextSize = 17
			buyButton.Text = "Not enought cash!"
			wait(.5)
			buyButton.TextSize = 30
			buyButton.Text = "Purchase"
		end
		end
end)

Amount.FocusLost:connect(function()
	c = 50
	wait()
	c = round(Amount.Text * c * 1.025^(v + Amount.Text) - 1)
		textLabel.Text = "($"..c..") Amateur Swordsman(Attack+1) Owned: ".. v
end)

repeat wait(0.01)
if game.Workspace.Shop.Visibility.Value == 1
	then
	buyButton.Visible = true
	textLabel.Visible = true
	Amount.Visible = true
elseif game.Workspace.Shop.Visibility.Value == 0
	then
	Amount.Visible = false
	buyButton.Visible = false
	textLabel.Visible = false
end
until game.Workspace.Shop.Visibility.Value == 2

A You didn't put the LocalPlayer script in a Local Script, or

B LocalPlayer hasn't loaded in before the script loads in. This will result in an error with Lua thinking that LocalPlayer never existed. You can fix it using WaitForChild().