Roblox chat GUI

clone = script.Parent.Default:Clone()

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fontsize = 18
buffer = 3
lines = 6

linesize = fontsize + buffer * 2
script.Parent.Size = UDim2.new(0.3, 0, 0, linesize * lines)
script.Parent.Default.Position = UDim2.new(0, 0, 0, linesize * lines - linesize)
script.Parent.Default.FontSize = "Size"..fontsize
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ranks = {   [1] = "Enlist",
            [2] = "Private",
            [3] = "Corporal",
            [4] = "Sergeant",
            [5] = "Staff Sergeant",
            [6] = "First Sergeant",
            [7] = "Sergeant Major",
            [8] = "Warrant Officer",
            [9] = "Second Lieutenant",
            [10] = "First Lieutenant",
            [11] = "CiT",
            [12] = "DP",
            [12+1] = "Captain",
            [13+1] = "Major",
            [14+1] = "Colonel",
            [15+1] = "Major General",
            [16+1] = "Lieutenant General",
            [17+1] = "General",
            [18+1] = "Commander"
}

function shiftup()
    for _, a in pairs(script.Parent:GetChildren()) do
        if a.Name == "Chat" then
            shared[a].True = shared[a].True + UDim2.new(0, 0, 0, -linesize)
            a:TweenPosition(shared[a].True, "Out", "Quad", 0.157, true)
        end
    end
end
function Chat(msg, plr, rankoverride)
    shiftup()
    local text = clone:Clone()
    text.Visible = true
    text.Text = msg
    text.Name = "Chat"
    if plr:IsInGroup(226584) or rankoverride then
        if not rankoverride then
            local rank = Player:GetRankInGroup(226584)
        else
            rank = rankoverride
        end
        text.Text = "["..ranks[rank].."] "..plr.Name..": "..text.Text
        if rank >= 13 then
            text.TextColor3 = Color3.new(0, 0, 127/225)
        else
            text.TextColor3 = Color3.new(28/225, 43/225, 1)
        end
    else
        text.Text = "[Visitor] "..plr.Name..": "..text.Text
    end
    text.Position = text.Position + UDim2.new(0, 0, 0, linesize)
    text.Parent = script.Parent
    text:TweenPosition(UDim2.new(0, 0, 0, linesize * lines - linesize), "Out", "Quad", 0.157, true)
    shared[text] = {}
    shared[text].True = UDim2.new(0, 0, 0, linesize * lines - linesize)
    Lines = text.TextBounds.Y / fontsize --18 is the font size
    for i = 1, Lines - 1 do
        shiftup()
    end
    text.Size = UDim2.new(1, 0, 0, linesize * Lines)
    game:GetService("Debris"):AddItem(text, 60)
end

game.Players.PlayerAdded:connect(function (plr)
    plr.Chatted:connect(function (m)
        Chat(m, plr)
    end)
end)

for _, plr in pairs(game.Players:GetChildren()) do
    plr.Chatted:connect(function (m)
        Chat(m, plr)
    end)
end

_G.chat = Chat