当玩家加入服务器时，Garry's Mod MOTD弹出所有人的屏幕

您可以使用以下代码：

function openLobby()
    local frame = vgui.Create("DFrame")
    frame:SetSize(ScrW(), ScrH())
    frame:Center()
    frame:SetVisible(true)
    frame:ShowCloseButton(false)
    frame:SetDraggable(false)
    frame:SetTitle("")

    frame.Paint = function(s, w, h)
        draw.RoundedBox(0, 0, 0, w, h, Color(0, 0, 0, 255))
    end

    frame:MakePopup()
    local startBut = vgui.Create("DButton", frame)
    startBut:SetSize(200, 75)
    startBut:SetPos(ScrW() / 2 - 100, ScrH() / 2 - (75 / 2))
    startBut:SetText("开始游戏")

    startBut.DoClick = function()
        net.Start("start_game")
        net.SendToServer()
        frame:Close()
    end
end

hook.Add("InitPostEntity", "onJoinStartGameWindow", function()
    timer.Simple(5, function()
        openLobby()
    end)
end)