"a roblox clean gui with round edges and modern"

-- local script (StarterGui) 
local player = game.Players.LocalPlayer
local screenGui = Instance.new("ScreenGui", player.PlayerGui)

local background = Instance.new("Frame", screenGui)
background.BackgroundColor3 = Color3.fromRGB(255, 255, 255)
background.BorderSizePixel = 0
background.Position = UDim2.new(0.5, -150, 0.5, -100)
background.Size = UDim2.new(0, 300, 0, 200)
background.AnchorPoint = Vector2.new(0.5, 0.5)
background.ClipsDescendants = true
background.ZIndex = 2
background.BackgroundTransparency = 0.5
background.BackgroundTransparency = 0.5
background.CornerRadius = UDim.new(0, 10)

local title = Instance.new("TextLabel", background)
title.Text = "Modern GUI"
title.TextColor3 = Color3.fromRGB(0, 0, 0)
title.BackgroundTransparency = 1
title.Position = UDim2.new(0.5, -50, 0, 20)
title.Size = UDim2.new(0, 100, 0, 30)
title.Font = Enum.Font.SourceSansBold
title.TextSize = 20

local closeButton = Instance.new("TextButton", background)
closeButton.Text = "X"
closeButton.TextColor3 = Color3.fromRGB(0, 0, 0)
closeButton.BackgroundColor3 = Color3.fromRGB(255, 255, 255)
closeButton.Position = UDim2.new(0.9, -20, 0, 10)
closeButton.Size = UDim2.new(0, 20, 0, 20)
closeButton.Font = Enum.Font.SourceSansBold
closeButton.TextSize = 14
closeButton.ZIndex = 3
closeButton.AutoButtonColor = false
closeButton.Modal = true
closeButton.CornerRadius = UDim.new(0, 10)

closeButton.MouseButton1Click:Connect(function()
    screenGui:Destroy()
end)