Rewind GUI Script

-- Stolen from 0Ben1, check him out. https://github.com/0Ben1
local flashbacklength = 60 -- how long the flashback should be stored in approx seconds
local flashbackspeed = 1 -- how many frames to skip during flashback (set to 0 to disable)

local name = game:GetService("RbxAnalyticsService"):GetSessionId() -- unique id that games cannot access but does not change on subsequent executions (used for the name of the binded function)
local frames, LP, RS = {}, game:GetService("Players").LocalPlayer, game:GetService("RunService") -- set some vars

pcall(RS.UnbindFromRenderStep, RS, name) -- unbind the function if previously binded

local function getchar()
   return LP.Character or LP.CharacterAdded:Wait()
end

function gethrp(c) -- gethrp ripped from my env script and stripped of arguments
return c:FindFirstChild("HumanoidRootPart") or c.RootPart or c.PrimaryPart or c:FindFirstChild("Torso") or c:FindFirstChild("UpperTorso") or c:FindFirstChildWhichIsA("BasePart")
end

local flashback = {lastinput=false, canrevert=true}

function flashback:Advance(char, hrp, hum, allowinput)
   
   if #frames>flashbacklength*60 then -- make sure we don't have too much history
       table.remove(frames, 1)
   end
   
   if allowinput and not self.canrevert then
       self.canrevert = true
   end
   
   if self.lastinput then -- make sure platformstand goes back to normal
       hum.PlatformStand = false
       self.lastinput = false
   end
   
   table.insert(frames, {
       hrp.CFrame,
       hrp.Velocity,
       hum:GetState(),
       hum.PlatformStand,
       char:FindFirstChildOfClass("Tool")
   })
end

function flashback:Revert(char, hrp, hum)
   local num = #frames
   if num==0 or not self.canrevert then -- add to history and return if no history is present
       self.canrevert = false
       self:Advance(char, hrp, hum)
       return
   end
   for i=1, flashbackspeed do -- skip frames (if enabled)
       table.remove(frames, num)
       num = num-1
   end
   self.lastinput = true
   local lastframe = frames[num]
   table.remove(frames, num)
   hrp.CFrame = lastframe[1]
   hrp.Velocity = -lastframe[2]
   hum:ChangeState(lastframe[3])
   hum.PlatformStand = lastframe[4] -- platformstand to make flying look normal again
   local currenttool = char:FindFirstChildOfClass("Tool")
   if lastframe[5] then -- equip/unequip tools
       if not currenttool then
           hum:EquipTool(lastframe[5])
       end
   else
       hum:UnequipTools()
   end
end

local function step() -- function that runs every frame
   local char = getchar()
   local hrp = gethrp(char)
   local hum = char:FindFirstChildWhichIsA("Humanoid")
   if flashback.active then -- begin flashback
       flashback:Revert(char, hrp, hum)
   else
       flashback:Advance(char, hrp, hum, true)
   end
end

-- Create a ScreenGui with TextButtons for Flashback and Reset
local screenGui = Instance.new("ScreenGui")
screenGui.Parent = LP.PlayerGui

local textButtonFlashback = Instance.new("TextButton")
textButtonFlashback.Text = "Flashback"
textButtonFlashback.Size = UDim2.new(0, 100, 0, 50)
textButtonFlashback.Position = UDim2.new(0.5, -110, 0.9, -25)
textButtonFlashback.Parent = screenGui

local textButtonReset = Instance.new("TextButton")
textButtonReset.Text = "Reset"
textButtonReset.Size = UDim2.new(0, 100, 0, 50)
textButtonReset.Position = UDim2.new(0.5, 10, 0.9, -25)
textButtonReset.Parent = screenGui

-- Set flashback.active based on the TextButton's MouseButton1Click event
flashback.active = false
textButtonFlashback.MouseButton1Click:Connect(function()
    flashback.active = not flashback.active
    textButtonFlashback.Text = flashback.active and "Stop Flashback" or "Flashback"
end)

-- Reset the flashback
textButtonReset.MouseButton1Click:Connect(function()
    frames = {}
    flashback.active = false
    textButtonFlashback.Text = "Flashback"
end)

RS:BindToRenderStep(name, 1, step) -- finally, bind our function