local container = Instance.new("Frame")
container.Name = "Container"
container.Size = UDim2.new(1, 0, 1, 0)
container.BackgroundTransparency = 1
container.BorderSizePixel = 0
container.Parent = screenGui
-- All UI children go under container, not directly under screenGui

-- Scale for responsive sizing
frame.Size = UDim2.new(0.5, 0, 0, 40)  -- 50% width, 40px height

-- Offset for UIStroke (Scale not supported)
stroke.Thickness = 2  -- always Offset

-- UICorner supports Scale
corner.CornerRadius = UDim.new(0, 8)    -- Offset
corner.CornerRadius = UDim.new(0.5, 0)  -- Scale (50% of smallest axis)

local Players = game:GetService("Players")
local player = Players.LocalPlayer
local playerGui = player:WaitForChild("PlayerGui")

local screenGui = Instance.new("ScreenGui")
screenGui.Name = "MainHUD"
screenGui.ResetOnSpawn = false -- survives respawn
screenGui.DisplayOrder = 10   -- higher renders on top
screenGui.IgnoreGuiInset = true -- extends behind top bar
screenGui.Parent = playerGui

local surfaceGui = Instance.new("SurfaceGui")
surfaceGui.Face = Enum.NormalId.Front
surfaceGui.SizingMode = Enum.SurfaceGuiSizingMode.PixelsPerStud
surfaceGui.PixelsPerStud = 50
surfaceGui.Parent = workspace.SignPart
-- Also set surfaceGui.Adornee = workspace.SignPart if parented elsewhere

local billboardGui = Instance.new("BillboardGui")
billboardGui.Size = UDim2.new(0, 200, 0, 50)
billboardGui.StudsOffset = Vector3.new(0, 3, 0) -- above the part
billboardGui.AlwaysOnTop = false -- occluded by 3D geometry
billboardGui.MaxDistance = 100   -- hides beyond this range
billboardGui.Adornee = workspace.NPC.Head
billboardGui.Parent = workspace.NPC.Head

DisplayOrder 100  -- Modal dialogs (on top of everything)
DisplayOrder 50   -- Notifications / toasts
DisplayOrder 10   -- HUD elements
DisplayOrder 1    -- Background UI

local frame = Instance.new("Frame")
frame.Size = UDim2.new(0.3, 0, 0.4, 0)         -- 30% width, 40% height
frame.Position = UDim2.new(0.5, 0, 0.5, 0)      -- centered (with AnchorPoint)
frame.AnchorPoint = Vector2.new(0.5, 0.5)
frame.BackgroundColor3 = Color3.fromRGB(30, 30, 40)
frame.BackgroundTransparency = 0.1
frame.BorderSizePixel = 0
frame.Parent = screenGui

local label = Instance.new("TextLabel")
label.Size = UDim2.new(1, 0, 0, 40)
label.Text = "Score: 0"
label.TextColor3 = Color3.fromRGB(255, 255, 255)
label.TextScaled = true
label.Font = Enum.Font.GothamBold
label.BackgroundTransparency = 1
label.Parent = frame

local button = Instance.new("TextButton")
button.Size = UDim2.new(0.5, 0, 0, 50)
button.Text = "Purchase"
button.TextColor3 = Color3.fromRGB(255, 255, 255)
button.BackgroundColor3 = Color3.fromRGB(0, 170, 80)
button.Font = Enum.Font.GothamBold
button.TextSize = 18
button.Parent = frame

button.Activated:Connect(function()
    -- Activated works for mouse click, touch tap, and gamepad
end)

local icon = Instance.new("ImageLabel")
icon.Size = UDim2.new(0, 64, 0, 64)
icon.Image = "rbxassetid://123456789"
icon.ScaleType = Enum.ScaleType.Fit
icon.BackgroundTransparency = 1
icon.Parent = frame

local viewport = Instance.new("ViewportFrame")
viewport.Size = UDim2.new(0, 200, 0, 200)
viewport.BackgroundColor3 = Color3.fromRGB(20, 20, 20)
viewport.Parent = frame

-- Clone a model into the viewport
local previewModel = workspace.SwordModel:Clone()
previewModel.Parent = viewport

-- Add a camera
local camera = Instance.new("Camera")
camera.CFrame = CFrame.new(Vector3.new(0, 2, 5), Vector3.new(0, 1, 0))
camera.Parent = viewport
viewport.CurrentCamera = camera

-- Rounded corners
local corner = Instance.new("UICorner")
corner.CornerRadius = UDim.new(0, 8)
corner.Parent = frame

-- Stroke/border
local stroke = Instance.new("UIStroke")
stroke.Color = Color3.fromRGB(255, 255, 255)
stroke.Thickness = 2
stroke.Transparency = 0.5
stroke.ApplyStrokeMode = Enum.ApplyStrokeMode.Border
stroke.Parent = frame

-- Gradient
local gradient = Instance.new("UIGradient")
gradient.Color = ColorSequence.new(
    Color3.fromRGB(50, 50, 80),
    Color3.fromRGB(20, 20, 40)
)
gradient.Rotation = 90
gradient.Parent = frame

-- Padding
local padding = Instance.new("UIPadding")
padding.PaddingLeft = UDim.new(0, 12)
padding.PaddingRight = UDim.new(0, 12)
padding.PaddingTop = UDim.new(0, 12)
padding.PaddingBottom = UDim.new(0, 12)
padding.Parent = frame

local listLayout = Instance.new("UIListLayout")
listLayout.FillDirection = Enum.FillDirection.Vertical
listLayout.HorizontalAlignment = Enum.HorizontalAlignment.Center
listLayout.VerticalAlignment = Enum.VerticalAlignment.Top
listLayout.SortOrder = Enum.SortOrder.LayoutOrder
listLayout.Padding = UDim.new(0, 8) -- gap between items
listLayout.Parent = frame

local gridLayout = Instance.new("UIGridLayout")
gridLayout.CellSize = UDim2.new(0, 80, 0, 80)
gridLayout.CellPadding = UDim2.new(0, 8, 0, 8)
gridLayout.FillDirection = Enum.FillDirection.Horizontal
gridLayout.FillDirectionMaxCells = 4 -- 4 columns, then wrap
gridLayout.SortOrder = Enum.SortOrder.LayoutOrder
gridLayout.HorizontalAlignment = Enum.HorizontalAlignment.Center
gridLayout.Parent = scrollFrame

local pageLayout = Instance.new("UIPageLayout")
pageLayout.Animated = true
pageLayout.EasingStyle = Enum.EasingStyle.Quad
pageLayout.EasingDirection = Enum.EasingDirection.InOut
pageLayout.TweenTime = 0.3
pageLayout.Circular = false    -- cannot loop from last to first
pageLayout.Padding = UDim.new(0, 0)
pageLayout.Parent = frame

-- Navigate pages
pageLayout:JumpToIndex(0)
pageLayout:Next()
pageLayout:Previous()
pageLayout:JumpTo(someChildFrame)

local sizeConstraint = Instance.new("UISizeConstraint")
sizeConstraint.MinSize = Vector2.new(200, 150)
sizeConstraint.MaxSize = Vector2.new(600, 450)
sizeConstraint.Parent = frame

local aspect = Instance.new("UIAspectRatioConstraint")
aspect.AspectRatio = 16 / 9
aspect.AspectType = Enum.AspectType.FitWithinMaxSize
aspect.DominantAxis = Enum.DominantAxis.Width
aspect.Parent = frame

local camera = workspace.CurrentCamera

local function adaptUI()
    local viewportSize = camera.ViewportSize
    local isPortrait = viewportSize.Y > viewportSize.X
    local isSmallScreen = viewportSize.X < 600

    if isSmallScreen then
        frame.Size = UDim2.new(0.95, 0, 0.8, 0)  -- nearly fullscreen on mobile
    elseif isPortrait then
        frame.Size = UDim2.new(0.7, 0, 0.5, 0)
    else
        frame.Size = UDim2.new(0.3, 0, 0.4, 0)   -- standard desktop
    end
end

camera:GetPropertyChangedSignal("ViewportSize"):Connect(adaptUI)
adaptUI()

local TweenService = game:GetService("TweenService")

-- TweenInfo.new(time, easingStyle, easingDirection, repeatCount, reverses, delayTime)
local tweenInfo = TweenInfo.new(
    0.5,                           -- duration in seconds
    Enum.EasingStyle.Quad,         -- easing curve
    Enum.EasingDirection.Out,      -- direction
    0,                             -- repeat count (0 = no repeat, -1 = infinite)
    false,                         -- reverses
    0                              -- delay before starting
)

-- Slide in from the right
frame.Position = UDim2.new(1.5, 0, 0.5, 0)

local slideIn = TweenService:Create(frame, TweenInfo.new(0.4, Enum.EasingStyle.Back, Enum.EasingDirection.Out), {
    Position = UDim2.new(0.5, 0, 0.5, 0),
})
slideIn:Play()

-- Fade in
frame.BackgroundTransparency = 1
local fadeIn = TweenService:Create(frame, TweenInfo.new(0.3), {
    BackgroundTransparency = 0,
})
fadeIn:Play()

-- Color transition
local colorShift = TweenService:Create(frame, TweenInfo.new(0.5), {
    BackgroundColor3 = Color3.fromRGB(255, 50, 50),
})
colorShift:Play()

-- Size pulse
local pulse = TweenService:Create(button, TweenInfo.new(0.6, Enum.EasingStyle.Sine, Enum.EasingDirection.InOut, -1, true), {
    Size = UDim2.new(0.55, 0, 0, 55),
})
pulse:Play()

local step1 = TweenService:Create(frame, TweenInfo.new(0.3), {
    Position = UDim2.new(0.5, 0, 0.5, 0),
})
local step2 = TweenService:Create(frame, TweenInfo.new(0.2), {
    Size = UDim2.new(0.4, 0, 0.5, 0),
})

step1.Completed:Connect(function()
    step2:Play()
end)
step1:Play()

-- Bounce entrance
local function bounceIn(element: GuiObject)
    element.Size = UDim2.new(0, 0, 0, 0)
    element.AnchorPoint = Vector2.new(0.5, 0.5)
    local tween = TweenService:Create(element, TweenInfo.new(0.5, Enum.EasingStyle.Back, Enum.EasingDirection.Out), {
        Size = UDim2.new(0.3, 0, 0.4, 0),
    })
    tween:Play()
    return tween
end

-- Fade + scale dismiss
local function dismiss(element: GuiObject): RBXScriptSignal
    local tween = TweenService:Create(element, TweenInfo.new(0.25, Enum.EasingStyle.Quad, Enum.EasingDirection.In), {
        Size = UDim2.new(0, 0, 0, 0),
        BackgroundTransparency = 1,
    })
    tween:Play()
    return tween.Completed
end

local UserInputService = game:GetService("UserInputService")

-- Keyboard input
UserInputService.InputBegan:Connect(function(input: InputObject, gameProcessed: boolean)
    if gameProcessed then return end -- ignore if typing in a TextBox, etc.

    if input.KeyCode == Enum.KeyCode.E then
        toggleInventory()
    elseif input.KeyCode == Enum.KeyCode.Escape then
        togglePauseMenu()
    end
end)

-- Mouse position
local mousePos = UserInputService:GetMouseLocation() -- Vector2

-- Detect platform
local isMobile = UserInputService.TouchEnabled and not UserInputService.KeyboardEnabled
local isConsole = UserInputService.GamepadEnabled

-- Hide mouse cursor
UserInputService.MouseIconEnabled = false

local ContextActionService = game:GetService("ContextActionService")

local function onInteract(actionName: string, inputState: Enum.UserInputState, inputObject: InputObject)
    if inputState == Enum.UserInputState.Begin then
        interactWithNearestObject()
    end
    return Enum.ContextActionResult.Sink -- consume the input
end

-- Bind to E key, touch button auto-created on mobile
ContextActionService:BindAction("Interact", onInteract, true, Enum.KeyCode.E)

-- Customize the mobile button
ContextActionService:SetPosition("Interact", UDim2.new(0.8, 0, 0.5, 0))
ContextActionService:SetTitle("Interact", "E")
ContextActionService:SetImage("Interact", "rbxassetid://123456789")

-- Unbind when no longer needed
ContextActionService:UnbindAction("Interact")

-- UITheme.luau (ModuleScript in ReplicatedStorage)
local Theme = {
    Colors = {
        Background = Color3.fromRGB(25, 25, 35),
        Surface = Color3.fromRGB(40, 40, 55),
        Primary = Color3.fromRGB(0, 150, 70),
        Danger = Color3.fromRGB(200, 40, 40),
        TextPrimary = Color3.fromRGB(255, 255, 255),
        TextSecondary = Color3.fromRGB(180, 180, 190),
        Accent = Color3.fromRGB(255, 215, 0),
    },
    Fonts = {
        Title = Enum.Font.GothamBold,
        Body = Enum.Font.Gotham,
        Mono = Enum.Font.RobotoMono,
    },
    TextSizes = {
        Title = 24,
        Subtitle = 18,
        Body = 14,
        Small = 12,
    },
    CornerRadius = UDim.new(0, 8),
    Padding = UDim.new(0, 12),
}

return Theme

local pool: { Frame } = {}

local function getCard(): Frame
    local card = table.remove(pool)
    if not card then
        card = createNewCard() -- only create if pool is empty
    end
    card.Visible = true
    return card
end

local function returnCard(card: Frame)
    card.Visible = false
    card.Parent = nil
    table.insert(pool, card)
end

-- BAD: breaks on different resolutions
frame.Position = UDim2.new(0, 500, 0, 300)
frame.Size = UDim2.new(0, 400, 0, 200)

-- GOOD: responsive
frame.Position = UDim2.new(0.5, 0, 0.5, 0)
frame.Size = UDim2.new(0.3, 0, 0.25, 0)
frame.AnchorPoint = Vector2.new(0.5, 0.5)

-- BAD: creates garbage every frame, causes lag
RunService.RenderStepped:Connect(function()
    local label = Instance.new("TextLabel")
    label.Text = `Score: ${score}`
    label.Parent = screenGui
end)

-- GOOD: update existing element
RunService.RenderStepped:Connect(function()
    scoreLabel.Text = `Score: ${score}`
end)

-- BAD: connection persists after UI is removed, leaks memory
button.Activated:Connect(function()
    doSomething()
end)

-- GOOD: store and disconnect
local connection = button.Activated:Connect(function()
    doSomething()
end)

-- When done:
connection:Disconnect()

-- OR use :Once() for single-fire events
button.Activated:Once(function()
    doSomething()
end)

-- BAD: freezes the entire UI
button.Activated:Connect(function()
    task.wait(5) -- nothing else can happen for 5 seconds
    label.Text = "Done"
end)

-- GOOD: use task.delay or task.spawn for async work
button.Activated:Connect(function()
    button.Active = false
    task.spawn(function()
        -- do async work
        task.wait(5)
        label.Text = "Done"
        button.Active = true
    end)
end)

-- BAD: client decides if purchase succeeds
button.Activated:Connect(function()
    coins -= item.price  -- client-side deduction, exploitable
end)

-- GOOD: server validates everything
button.Activated:Connect(function()
    local success = purchaseRemote:InvokeServer(itemId)
    if success then
        updateCoinsDisplay()
    end
end)

-- BAD: only works with mouse
button.MouseButton1Click:Connect(handler)

-- GOOD: works on mouse, touch, and gamepad
button.Activated:Connect(handler)

local UserInputService = game:GetService("UserInputService")

local function isTouchDevice(): boolean
    return UserInputService.TouchEnabled and not UserInputService.KeyboardEnabled
end

-- Apply at UI creation time
if isTouchDevice() then
    button.Size = UDim2.new(button.Size.X.Scale * 1.4, 0, button.Size.Y.Scale * 1.4, 0)
end

local preferred = UserInputService.PreferredInput
-- Enum.PreferredInput values:
--   Touch, MouseAndKeyboard, Gamepad, None

if preferred == Enum.PreferredInput.Touch then
    -- enlarge buttons, simplify layout
elseif preferred == Enum.PreferredInput.Gamepad then
    -- highlight focused element, add navigation hints
end

UserInputService:GetPropertyChangedSignal("PreferredInput"):Connect(function()
    -- re-adapt UI when input method changes
end)

local uiScale = Instance.new("UIScale")
uiScale.Scale = math.min(1, camera.ViewportSize.X / 1080) -- reference width
uiScale.Parent = screenGui

local GuiService = game:GetService("GuiService")

-- Set the initially selected object when opening a menu
GuiService.SelectedObject = myButton

-- On menu close, clear selection
GuiService.SelectedObject = nil

-- BAD: text scales to fit, becomes unreadable on small screens
label.TextScaled = true

-- GOOD: label grows/shrinks to fit text at fixed readable size
label.TextSize = 16
label.TextWrapped = true
label.AutomaticSize = Enum.AutomaticSize.Y -- height adjusts to content

local textSizeConstraint = Instance.new("UITextSizeConstraint")
textSizeConstraint.MaxTextSize = 24
textSizeConstraint.MinTextSize = 12 -- NEVER below 9 (official hard rule)
textSizeConstraint.Parent = label

label.TextTruncate = Enum.TextTruncate.AtEnd -- shows "..." when text overflows
label.TextWrapped = true -- wrap instead of truncate for multi-line content

local TextService = game:GetService("TextService")

local bounds = TextService:GetTextSize(
    "Hello World",
    16,                -- TextSize
    Enum.Font.Gotham,
    Vector2.new(200, math.huge) -- max width, unlimited height
)
-- bounds.X = actual width, bounds.Y = actual height

-- Style rules can target by class, tag, name, state, modifier, query
-- Similar to CSS selectors

-- BAD: manually calculating canvas size
scrollFrame.CanvasSize = UDim2.new(0, 0, 0, listLayout.AbsoluteContentSize.Y)

-- GOOD: engine handles it automatically
scrollFrame.AutomaticCanvasSize = Enum.AutomaticSize.Y
scrollFrame.ScrollingDirection = Enum.ScrollingDirection.Y

local scrollFrame = Instance.new("ScrollingFrame")
scrollFrame.Size = UDim2.new(1, 0, 1, 0)
scrollFrame.BackgroundTransparency = 1
scrollFrame.ScrollBarThickness = 6
scrollFrame.AutomaticCanvasSize = Enum.AutomaticSize.Y
scrollFrame.ScrollingDirection = Enum.ScrollingDirection.Y
scrollFrame.Parent = container

local listLayout = Instance.new("UIListLayout")
listLayout.FillDirection = Enum.FillDirection.Vertical
listLayout.Padding = UDim.new(0, 8)
listLayout.SortOrder = Enum.SortOrder.LayoutOrder
listLayout.Parent = scrollFrame

-- Add items as children of scrollFrame
-- They auto-arrange vertically, scrollFrame auto-sizes

local scrollFrame = Instance.new("ScrollingFrame")
scrollFrame.AutomaticCanvasSize = Enum.AutomaticSize.Y
scrollFrame.ScrollingDirection = Enum.ScrollingDirection.Y
scrollFrame.Parent = container

local gridLayout = Instance.new("UIGridLayout")
gridLayout.CellSize = UDim2.new(0, 80, 0, 80)
gridLayout.CellPadding = UDim2.new(0, 8, 0, 8)
gridLayout.FillDirectionMaxCells = 4 -- 4 columns
gridLayout.SortOrder = Enum.SortOrder.LayoutOrder
gridLayout.Parent = scrollFrame

scrollFrame.ElasticBehavior = Enum.ElasticBehavior.Never