-- LocalScript: put this inside StarterGui (Roblox Studio)
local Players = game:GetService("Players")
local UserInputService = game:GetService("UserInputService")
local TweenService = game:GetService("TweenService")

local player = Players.LocalPlayer

-- Theme
local COLORS = {
	bg = Color3.fromRGB(24, 24, 28),
	screen = Color3.fromRGB(14, 14, 17),
	number = Color3.fromRGB(52, 52, 60),
	func = Color3.fromRGB(86, 86, 98),
	op = Color3.fromRGB(255, 149, 0),
	text = Color3.new(1, 1, 1),
	dim = Color3.fromRGB(150, 150, 160),
}
local MAX_DIGITS = 12

-- GUI
local gui = Instance.new("ScreenGui")
gui.Name = "Calculator"
gui.ResetOnSpawn = false
gui.Parent = player:WaitForChild("PlayerGui")

local frame = Instance.new("Frame")
frame.Size = UDim2.fromOffset(272, 400)
frame.Position = UDim2.fromScale(0.5, 0.5)
frame.AnchorPoint = Vector2.new(0.5, 0.5)
frame.BackgroundColor3 = COLORS.bg
frame.Active = true
frame.Draggable = true
frame.Parent = gui
Instance.new("UICorner", frame).CornerRadius = UDim.new(0, 14)

local title = Instance.new("TextLabel")
title.Size = UDim2.new(1, -28, 0, 30)
title.Position = UDim2.fromOffset(14, 0)
title.BackgroundTransparency = 1
title.Text = "Calculator"
title.TextColor3 = COLORS.dim
title.TextXAlignment = Enum.TextXAlignment.Left
title.Font = Enum.Font.GothamMedium
title.TextSize = 14
title.Parent = frame

local history = Instance.new("TextLabel")
history.Size = UDim2.new(1, -24, 0, 18)
history.Position = UDim2.fromOffset(12, 34)
history.BackgroundTransparency = 1
history.Text = ""
history.TextColor3 = COLORS.dim
history.TextXAlignment = Enum.TextXAlignment.Right
history.Font = Enum.Font.Code
history.TextSize = 14
history.Parent = frame

local display = Instance.new("TextLabel")
display.Size = UDim2.new(1, -24, 0, 50)
display.Position = UDim2.fromOffset(12, 54)
display.BackgroundColor3 = COLORS.screen
display.TextColor3 = COLORS.text
display.TextXAlignment = Enum.TextXAlignment.Right
display.TextScaled = true
display.Font = Enum.Font.Code
display.Text = "0"
display.Parent = frame
Instance.new("UICorner", display)
local pad = Instance.new("UIPadding", display)
pad.PaddingRight = UDim.new(0, 10)
pad.PaddingTop = UDim.new(0, 6)
pad.PaddingBottom = UDim.new(0, 6)

-- Calculator logic
local current, stored, op, fresh = "0", nil, nil, false
local OP_LABEL = { ["+"] = "+", ["-"] = "−", ["×"] = "×", ["÷"] = "÷" }

local function fmt(n)
	if n ~= n or n == math.huge or n == -math.huge then return "Error" end
	local a = math.abs(n)
	if a >= 1e12 or (a < 1e-9 and n ~= 0) then
		return string.format("%.6g", n)
	end
	return string.format("%.10g", n)
end

local function compute(a, b, o)
	if o == "+" then return a + b end
	if o == "-" then return a - b end
	if o == "×" then return a * b end
	if o == "÷" then
		if b == 0 then return nil end
		return a / b
	end
end

local function render()
	display.Text = current
end

local function fail()
	current, stored, op, fresh = "0", nil, nil, true
	history.Text = ""
	display.Text = "Error"
end

local function clearAll()
	current, stored, op, fresh = "0", nil, nil, false
	history.Text = ""
	render()
end

local function press(key)
	if display.Text == "Error" then clearAll() end

	if tonumber(key) then
		if fresh or current == "0" then
			current = key
			fresh = false
		elseif #current:gsub("[%-%.]", "") < MAX_DIGITS then
			current ..= key
		end
		render()

	elseif key == "." then
		if fresh then
			current = "0."
			fresh = false
		elseif not current:find("%.") then
			current ..= "."
		end
		render()

	elseif key == "C" then
		clearAll()

	elseif key == "⌫" then
		if fresh then return end
		current = current:sub(1, -2)
		if current == "" or current == "-" then current = "0" end
		render()

	elseif key == "±" then
		if current ~= "0" then
			current = current:sub(1, 1) == "-" and current:sub(2) or ("-" .. current)
		end
		render()

	elseif key == "%" then
		current = fmt(tonumber(current) / 100)
		fresh = true
		render()

	elseif key == "=" then
		if op and stored then
			local b = tonumber(current)
			local result = compute(stored, b, op)
			if result == nil then fail() return end
			history.Text = fmt(stored) .. " " .. OP_LABEL[op] .. " " .. fmt(b) .. " ="
			current = fmt(result)
			stored, op, fresh = nil, nil, true
			render()
		end

	else -- operator: + - × ÷
		if op and stored and not fresh then
			local result = compute(stored, tonumber(current), op)
			if result == nil then fail() return end
			stored = result
			current = fmt(result)
			render()
		elseif not (op and fresh) then
			stored = tonumber(current)
		end
		op = key
		fresh = true
		history.Text = fmt(stored) .. " " .. OP_LABEL[key]
	end
end

-- Buttons
local layout = {
	{ "C", "⌫", "%", "÷" },
	{ "7", "8", "9", "×" },
	{ "4", "5", "6", "-" },
	{ "1", "2", "3", "+" },
	{ "±", "0", ".", "=" },
}

local buttons = {}
local function baseColor(key)
	if tonumber(key) or key == "." then return COLORS.number end
	if key == "C" or key == "⌫" or key == "%" or key == "±" then return COLORS.func end
	return COLORS.op
end

local function tweenColor(btn, color)
	TweenService:Create(btn, TweenInfo.new(0.1), { BackgroundColor3 = color }):Play()
end

local function flash(key)
	local btn = buttons[key]
	if not btn then return end
	local base = baseColor(key)
	btn.BackgroundColor3 = base:Lerp(Color3.new(1, 1, 1), 0.35)
	tweenColor(btn, base)
end

for row, keys in ipairs(layout) do
	for col, key in ipairs(keys) do
		local btn = Instance.new("TextButton")
		btn.Size = UDim2.fromOffset(56, 48)
		btn.Position = UDim2.fromOffset(12 + (col - 1) * 64, 114 + (row - 1) * 56)
		btn.Text = OP_LABEL[key] or key
		btn.TextSize = 22
		btn.Font = Enum.Font.GothamBold
		btn.TextColor3 = COLORS.text
		btn.AutoButtonColor = false
		btn.BackgroundColor3 = baseColor(key)
		btn.Parent = frame
		Instance.new("UICorner", btn).CornerRadius = UDim.new(0, 10)
		buttons[key] = btn

		btn.MouseEnter:Connect(function()
			tweenColor(btn, baseColor(key):Lerp(Color3.new(1, 1, 1), 0.15))
		end)
		btn.MouseLeave:Connect(function()
			tweenColor(btn, baseColor(key))
		end)
		btn.Activated:Connect(function()
			flash(key)
			press(key)
		end)
	end
end

-- Keyboard support (works while the calculator is open)
local KEYMAP = {
	[Enum.KeyCode.Period] = ".", [Enum.KeyCode.KeypadPeriod] = ".",
	[Enum.KeyCode.Return] = "=", [Enum.KeyCode.KeypadEnter] = "=", [Enum.KeyCode.Equals] = "=",
	[Enum.KeyCode.Minus] = "-", [Enum.KeyCode.KeypadMinus] = "-",
	[Enum.KeyCode.Slash] = "÷", [Enum.KeyCode.KeypadDivide] = "÷",
	[Enum.KeyCode.KeypadMultiply] = "×", [Enum.KeyCode.Asterisk] = "×",
	[Enum.KeyCode.KeypadPlus] = "+", [Enum.KeyCode.Plus] = "+",
	[Enum.KeyCode.Backspace] = "⌫",
	[Enum.KeyCode.Delete] = "C", [Enum.KeyCode.Escape] = "C",
}
local DIGITS = { "Zero", "One", "Two", "Three", "Four", "Five", "Six", "Seven", "Eight", "Nine" }
for i, name in ipairs(DIGITS) do
	KEYMAP[Enum.KeyCode[name]] = tostring(i - 1)
	KEYMAP[Enum.KeyCode["Keypad" .. name]] = tostring(i - 1)
end

UserInputService.InputBegan:Connect(function(input, processed)
	if processed or not frame.Visible then return end
	local key = KEYMAP[input.KeyCode]
	if not key then return end

	local shift = UserInputService:IsKeyDown(Enum.KeyCode.LeftShift)
		or UserInputService:IsKeyDown(Enum.KeyCode.RightShift)
	if shift and input.KeyCode == Enum.KeyCode.Equals then key = "+" end
	if shift and input.KeyCode == Enum.KeyCode.Eight then key = "×" end

	flash(key)
	press(key)
end)