A game based on word scramble , the idea is to find out what the scrambled word is.

DuoJumbles.user.js

// ==UserScript==
// @name         DuoJumbles
// @namespace    http://your.homepage/
// @version      1.0a
// @description  A game based on word scramble , the idea is to find out what the scrambled word is.
// @author       Dessamator
// @include      https://www.duolingo.com/*
// @grant        none
// ==/UserScript==

//Add code to leave double words alone or "au secours".gmatch(/(\S+)\s+(\S+)/)
function inject(f) { //Inject the script into the document
    var script = document.createElement('script');
    script.type = 'text/javascript';
    script.setAttribute('name', 'DuoJumbles');
    script.textContent = '(' + f.toString() + ')(jQuery)';
    document.head.appendChild(script);
}
inject(f);

function f($) {
    var bLoading = false;
    var bNewGame = false;
    var mSndRight = new Audio("https://s3.amazonaws.com/duolingo-data/s3/sounds/right_answer.mp3");
    var mSndWrong = new Audio("https://s3.amazonaws.com/duolingo-data/s3/sounds/wrong_answer.mp3");
    var arrWords ;
    var arrWordsOriginal ;
    var iMaxWordsRound =2;
    var iMaxWordsVal = 6;

    $(document).ajaxComplete(function () {
        try{
            if (!$('#app').hasClass('home')) {
                bLoading = false;
            }
            main();

            if (!$("#DuoJumblesStore").length && $(".store-section").length ) {
                var $StoreItem = '<div class="store-section" id="DuoJumblesStore">'+
                    '<h5 class="gray">Games</h5><ul class="store-shelf">'+
                    '<li><span id="jumblesowlpic2" style="float:left; background-position: -650px 0px;"'+
                    'class="store-icon owl owl-mini"></span><a id="StoreJumblesPurchase" class="item-purchase '+
                    'btn btn-green right" data-type="duojumbles"><span class="margin-right">Get for:</span><span'+
                    'class="icon icon-lingot-small"></span><span class="price">1</span>'+
                    '</a><h4>DuoJumbles</h4><p>Jumbles is a word scramble game.</p></li></ul></div>';

                $(".store-section").parent().prepend($StoreItem);

                $("#StoreJumblesPurchase").on("click", function() {
                    if (duo.user.get("rupees")>1 && $("#jumbles_game").length){
                        var $PiperPayment = payPiper(1,true);
                        $PiperPayment.then(function(data){
                            $("#num_lingots").text($("#num_lingots").text()-1);
                            $("#num_lingots").text( duo.user.get("rupees")); 
                            $('#btnjumblesgame').removeAttr("disabled");
                            $("#StoreJumblesPurchase").attr("disabled","");
                            $("#jumbles_game").show();
                        },function(data){
                            //Piper not paid
                            $("#BotMsg").html("Error. Something went wrong while paying.");
                            return ;
                        });   
                    } else if (!$("#jumbles_game").length){
                        alert("Please refresh the page before playing (you may have switched languages).");
                    }
                    else{
                        alert("You do not have enough $£€¥.");
                    }
                }); 
            }
        }
        catch(e){
            console.log(e);
        }
    });

    function main(){
        if ($('#app').hasClass('home') && (!$("#jumbles_game").length ) && !bLoading) {
            var secondsSince = 0;       
            var startCounterVar;
            var iTry =3;
            var bTimerOn=false;
            var sVer = "1";
            var arrGameWords ={currword:"",scrambledword:""};

            var arrGameStatus;
            var $vocabAJax =$.ajax({dataType: "json", url: "https://www.duolingo.com/vocabulary/overview"});
            bLoading = true;
            bNewGame = false;

            if (!$("#jumbles_game").length ) {
                $("section.sidebar-left > div.inner")
                .prepend('<div id="jumbles_game" class="box-colored bg-white" style="display:none">'+
                         '<span id="jumblesowlpic" style="float:right" class="owl owl-mini"></span>'+
                         '<h2><span data-toggle="tooltip" title="" class="right" data-original-title="Close"'+
                         'id="jumbles_close">x</span>Jumbles</h2><div id="newjumbledword"></div><div id="BotMsg"></div>'+
                         '<a id="btnjumblesgame" href="javascript:;" class="btn btn-primary ">New game</a>'+
                         '<textarea type="text"  name="jumblesinputbox" value="" style="display:none ; overflow: hidden;'+
                         'word-wrap: break-word; resize: none; height: 30px;" class="textarea-block" id="jumblesinput"></textarea>'+
                         '<a id="btncheckanswer" href="javascript:;" class="btn btn-primary" style="display:none">Check</span></div>');
            }

            $('#btnjumblesgame').on("click", function(){
                setOwl("sporty");

                $('#btnjumblesgame').hide();
                $("#jumblesinput").val("");
                $("#jumblesinput").show();
                bLoading = true;
                main();

                arrGameStatus = {iScore:0,iWordCount:0,iMaxWords:iMaxWordsVal,iTries:iTry,iRound:1,iTotRounds:3};

                $("#newjumbledword").html("Loading words ...");
                if (!arrWords) {
                    $vocabAJax.then(function(data){

                        arrWordsOriginal = data.vocab_overview;
                        arrWords = arrWordsOriginal.slice();
                        if (arrWords.length>14){
                            arrGameStatus.iTotRounds = 3;
                        }
                        arrGameWords=startGame(arrGameWords,arrGameStatus);
                        $("#btncheckanswer").show();
                    });
                }
                else{
                    arrWords = arrWordsOriginal.slice();
                    if (arrWords.length>14){
                        arrGameStatus.iTotRounds = 3;
                    }
                    arrGameWords=startGame(arrGameWords,arrGameStatus);
                    $("#btncheckanswer").show();

                }
                $("#jumblesinput").focus();
                $("#BotMsg").html("");

            });

            $("#jumbles_close").on("click",function(){
                $("#StoreJumblesPurchase").removeAttr("disabled");
                $("#jumbles_game").fadeOut();
            });

            $('#btncheckanswer').on("click", function(){
                checkAnswer(arrGameWords,arrGameStatus);
            });

            $('#jumblesinput').keydown(function(e) {
                try{
                    if (e.which === 13) {
                        var sMsg = $('#jumblesinput').val();
                        if (!arrGameWords || sMsg.length<1 || sMsg==="\n") {
                            $('#jumblesinput').val("");
                            return ;
                        }
                        checkAnswer(arrGameWords,arrGameStatus);
                        event.preventDefault();
                        return;
                    }
                }
                catch(error){
                    console.log(error);
                }
            });
        }
    }

    function startGame(arrGameWords,arrGameStatus){
        sendUserMsg("",arrGameStatus);        
        return newWord(arrGameWords,arrGameStatus);
    }

    function setOwl (sType){
        if (sType=="sad"){
            $("#jumblesowlpic.owl").css("background-position","-80px -300px");
        }
        else if (sType=="sporty"){
            $("#jumblesowlpic.owl").css("background-position","-650px 0");   
        }
        else if (sType=="winner"){
            $("#jumblesowlpic.owl").css("background-position","-80px -80px");
        }
    }
    function newWord(arrGameWords,arrGameStatus){  
        if (arrGameWords.currword !=="") {   
            sendUserMsg("The last word was: "+arrGameWords.currword,arrGameStatus );
        }

        arrGameWords = scramble(arrWords,arrGameWords,arrGameStatus);
        $("#newjumbledword").html("New word is: <strong>"+ arrGameWords.scrambledword+"</strong>");
        return arrGameWords;
    }

    function checkAnswer(arrGameWords,arrGameStatus){
        if (arrWords && arrWords.length>0){
            var sMsg = $('#jumblesinput').val();

            if (sMsg===arrGameWords.currword  ) {
                if (arrGameStatus.iWordCount<arrGameStatus.iMaxWords){
                    arrGameStatus.iTries=3;
                }
                $('#jumblesinput').val("");
                mSndRight.play();
                setOwl("sporty");
                arrGameStatus.iScore =arrGameStatus.iScore + 1;
                arrGameWords = newWord(arrGameWords,arrGameStatus);
                sendUserMsg("Right!",arrGameStatus);

                if (arrGameStatus.iWordCount % iMaxWordsRound ===0 &&
                    arrGameStatus.iScore <arrGameStatus.iMaxWords -1) {
                    arrGameStatus.iRound++;
                }
            }else{  
                setOwl("sad");
                arrGameStatus.iTries= arrGameStatus.iTries-1;
                if (arrGameStatus.iTries<1 && (arrGameStatus.iWordCount<arrGameStatus.iMaxWords)){
                    arrGameStatus.iTries=3;
                    arrGameWords = newWord(arrGameWords,arrGameStatus);
                }
                else{
                    sendUserMsg(arrGameStatus.iTries + " tries left.",arrGameStatus );                       
                }
                mSndWrong.play();
            }

            if (arrGameStatus.iWordCount > arrGameStatus.iMaxWords ){
                var iTotScore = arrGameStatus.iScore / arrGameStatus.iMaxWords  ;

                sendUserMsg("Game over!",arrGameStatus);
                $("#jumblesinputbox").html("");
                $("#newjumbledword").html("");
                $("#jumblesinput").hide();
                $("#btncheckanswer").hide();
                $('#btnjumblesgame').attr("disabled","disabled");
                $('#btnjumblesgame').show();

                if(iTotScore== 1){
                    setOwl("winner");
                    sendUserMsg("Perfection, well done.",arrGameStatus);
                }else if(iTotScore> 0.5){
                    setOwl("winner");
                    sendUserMsg("Not bad!",arrGameStatus);
                }

                bLoading =false;
                $("#StoreJumblesPurchase").removeAttr("disabled");
                return arrGameWords;

            }
            $("#jumblesinput").val("");
            return arrGameWords;
        }
    }

    function scramble(arrWords,arrGameWords,arrGameStatus) {
        var x= Math.floor(Math.random() * arrWords.length);
        var sSentence="";   
        arrGameStatus.iWordCount += 1;

        if (x>arrWords.length){
            x=0;
        }
        else if (arrWords.length===0){
            return ; 
        }
        arrGameWords.currword =arrWords[x].word_string.toLowerCase();
        var arrSentenceWords = arrGameWords.currword.match(/(\S+)/g);

        arrWords.splice(x, 1);

        function scrambleEachWord(currword) {
            var sText =[];
            var sTmp,sTmp1 ="";

            sText = currword.split("");  
            for (var i=0;i<sText.length;i++ ) {
                var iRand = Math.floor((Math.random() * sText.length) +1);

                if(sText[iRand]){
                    sTmp = sText[i];
                    sTmp1 = sText[iRand];
                    sText[i] = sTmp1;
                    sText[iRand] =  sTmp;
                }
            }
            var oTmp = sText.toString();
            var scrambledword=oTmp.replace(/,/g, "").toLowerCase();
            return scrambledword;
        }
        for (var j = 0; j < arrSentenceWords.length; j ++){
            sSentence =sSentence+scrambleEachWord(arrSentenceWords[j]) + " ";
        }
        arrGameWords.scrambledword = sSentence;
        return arrGameWords;
    }

    function sendUserMsg(sMsg,arrGameStatus){
        var sScoreText = "Score :"+arrGameStatus.iScore +"/"+arrGameStatus.iMaxWords +"<br>"+
            "Round: "+ arrGameStatus.iRound +"<br>";
        $("#BotMsg").html(sScoreText + sMsg);
    }

    function payPiper(iLingots,bDebug){
        var URL = "https://www.duolingo.com/comments/1059877/love";
        var $PiperPayment =$.ajax({dataType: "json",type:"post", url: URL});
        return $PiperPayment;
    }
}