decaying winter script kill all npc

-- kill npc gui
local screenGui = Instance.new("ScreenGui")
screenGui.Name = "KillAllNPCs"
screenGui.ResetOnSpawn = false

local button = Instance.new("TextButton")
button.Size = UDim2.new(0, 200, 0, 50)
button.Position = UDim2.new(0.5, -100, 0.5, -25)
button.Text = "Start kill"
button.Font = Enum.Font.SourceSansBold
button.TextSize = 20
button.BackgroundColor3 = Color3.new(0.3, 0.7, 0.3)
button.BorderSizePixel = 0

button.Parent = screenGui
screenGui.Parent = game.Players.LocalPlayer:WaitForChild("PlayerGui")

local dragging = false
local dragInput, mousePos, framePos

local function update(input)
    local delta = input.Position - mousePos
    button.Position = UDim2.new(framePos.X.Scale, framePos.X.Offset + delta.X, framePos.Y.Scale, framePos.Y.Offset + delta.Y)
end

button.InputBegan:Connect(function(input)
    if input.UserInputType == Enum.UserInputType.MouseButton1 or input.UserInputType == Enum.UserInputType.Touch then
        dragging = true
        mousePos = input.Position
        framePos = button.Position

        input.Changed:Connect(function()
            if input.UserInputState == Enum.UserInputState.End then
                dragging = false
            end
        end)
    end
end)

button.InputChanged:Connect(function(input)
    if dragging and (input.UserInputType == Enum.UserInputType.MouseMovement or input.UserInputType == Enum.UserInputType.Touch) then
        dragInput = input
    end
end)

game:GetService("UserInputService").InputChanged:Connect(function(input)
    if dragging and input == dragInput then
        update(input)
    end
end)

local function killAllNPCs()
    while wait(0.01) do
        for _, d in ipairs(game.Workspace:GetDescendants()) do
            if d:IsA("Humanoid") then
                local isPlayer = false
                for _, player in ipairs(game.Players:GetPlayers()) do
                    if d.Parent == player.Character then
                        isPlayer = true
                        break
                    end
                end
                if not isPlayer then
                    d.Health = -1
                    d:ChangeState(Enum.HumanoidStateType.Dead)
                    d:TakeDamage(9999999999)
                end
            end
        end
    end
end

local isKilling = false
button.MouseButton1Click:Connect(function()
    if not dragging then
        if isKilling then
            isKilling = false
            button.Text = "Start kill"
            button.BackgroundColor3 = Color3.new(0.3, 0.7, 0.3)
        else
            isKilling = true
            button.Text = "Stop kill"
            button.BackgroundColor3 = Color3.new(1, 0, 0)
            coroutine.resume(coroutine.create(killAllNPCs))
        end
    end
end)