See players in server through walls

-- // AETHER ECHO-LOCATOR v2.0 (TEACHER-CORRECTED) \\ --
-- Applied Fixes: ~=, FillTransparency, :Connect, pcall logic

local Players = game:GetService("Players")
local TweenService = game:GetService("TweenService")
local UserInputService = game:GetService("UserInputService")

local player = Players.LocalPlayer
-- Fix: Targeting PlayerGui instead of StarterGui
local pGui = player:WaitForChild("PlayerGui")

-- // UI CONSTRUCTION \\ --
local sg = Instance.new("ScreenGui")
sg.Name = "MasterUniqueSystem"
sg.ResetOnSpawn = false -- Fix: Persists through death
sg.Parent = pGui

local main = Instance.new("Frame")
main.Size = UDim2.fromOffset(200, 100)
main.Position = UDim2.new(0.5, -100, 0.2, 0)
main.BackgroundColor3 = Color3.fromRGB(20, 20, 25)
main.Active = true -- Fix: Required for dragging
main.Parent = sg

Instance.new("UICorner", main).CornerRadius = UDim.new(0, 8)

-- // DRAGGABLE ENGINE \\ --
local function MakeDraggable(obj)
	local dragging, dragInput, dragStart, startPos
	obj.InputBegan:Connect(function(input)
		if input.UserInputType == Enum.UserInputType.MouseButton1 or input.UserInputType == Enum.UserInputType.Touch then
			dragging = true
			dragStart = input.Position
			startPos = obj.Position
			input.Changed:Connect(function()
				if input.UserInputState == Enum.UserInputState.End then dragging = false end
			end)
		end
	end)
	obj.InputChanged:Connect(function(input)
		if dragging and (input.UserInputType == Enum.UserInputType.MouseMovement or input.UserInputType == Enum.UserInputType.Touch) then
			local delta = input.Position - dragStart
			obj.Position = UDim2.new(startPos.X.Scale, startPos.X.Offset + delta.X, startPos.Y.Scale, startPos.Y.Offset + delta.Y)
		end
	end)
end
MakeDraggable(main)

-- // THE ECHO COMMAND \\ --
local function RunEchoPing()
	-- Fix: for loop with ipairs for GetPlayers result
	for _, p in ipairs(Players:GetPlayers()) do
		-- Fix: Use ~= instead of !=
		if p ~= player then
			local char = p.Character
			-- Fix: if char then check to avoid indexing nil
			if char then
				-- Cleanup old pings
				local old = char:FindFirstChild("EchoPing")
				if old then old:Destroy() end
				
				-- Fix: Use pcall for potential Instance errors
				local success, highlight = pcall(function()
					local h = Instance.new("Highlight")
					h.Name = "EchoPing"
					h.FillColor = Color3.fromRGB(0, 255, 150)
					h.OutlineColor = Color3.new(1, 1, 1)
					-- Fix: Correct property names (Transparency, not Alpha)
					h.FillTransparency = 0.4 
					h.OutlineTransparency = 0
					h.DepthMode = Enum.HighlightDepthMode.AlwaysOnTop
					h.Parent = char
					return h
				end)
				
				if success and highlight then
					task.spawn(function()
						local info = TweenInfo.new(1.5, Enum.EasingStyle.Sine, Enum.EasingDirection.Out)
						local tween = TweenService:Create(highlight, info, {
							FillTransparency = 1,
							OutlineTransparency = 1
						})
						tween:Play()
						tween.Completed:Wait()
						if highlight then highlight:Destroy() end
					end)
				end
			end
		end
	end
end

local btn = Instance.new("TextButton")
btn.Size = UDim2.new(0.9, 0, 0.6, 0)
btn.Position = UDim2.new(0.05, 0, 0.2, 0)
btn.Text = "PING PLAYERS"
btn.BackgroundColor3 = Color3.fromRGB(40, 40, 60)
btn.TextColor3 = Color3.new(1, 1, 1)
btn.Font = Enum.Font.GothamBold
btn.Parent = main
Instance.new("UICorner", btn)

-- Fix: Ensure :Connect() is called
btn.MouseButton1Click:Connect(RunEchoPing)

print("Echo System v2.0 Online. All teacher fixes applied.")