Introduction to forks

Code

fromFen("rnb1kbnr/ppp2ppp/3p4/3Np1q1/4P3/8/PPPP1PPP/R1BQKBNR w KQkq - 0 1");

let steps = [];
let targetMove = "";

steps.push(function() {
   info("A fork is when you attack two pieces at the same time.\
   <br>Play Nxc7+ to attack both the king and rook");
   
   targetMove = "Nxc7+";
});

steps.push(function() {
   performMove("Kd8");
   nextDelayed();
});

steps.push(function() {
   info("Our opponent has had to move their king out of check, leaving us free to take their rook.\
   Take the rook on a8 to continue.");
   
   targetMove = "Nxa8";
});

steps.push(function() {
   info("Perfect!\
   <br>The knight is the perfect piece to create forks, but other pieces can be used too.");
   showNextButton(true);
});

steps.push(function() {
   fromFen("rn1qkb1r/ppp1pppp/3p4/3n1b2/8/3P1N2/PPP1PPPP/RNBQKB1R w KQkq - 0 1");
   info("Find the move that creates a fork in this situation");
   targetMove = "e4";
});

steps.push(function() {
   info("Perfect!");
   showNextButton(true);
});

steps.push(function() {
    fromFen("r2q1rk1/ppp3pp/2n5/1b3Q2/3pP3/2NPnP2/PPP2NPP/2R2RK1 w q - 0 1");
   info("Sometimes it is possible to escape a fork.\
   <br>Move the queen to put our opponent in check, creating extra time to move our rook out of harm.");
   targetMove = "Qe6+";
});

steps.push(function() {
   performMove("Rf7");
   nextDelayed();
});

steps.push(function() {
   info("Now you can move your rook out of threat.");
   targetMove = "Rfe1";
});

steps.push(function() {
   info("Perfect");
   complete();
});

onPieceClicked(function (squareName) {
    if(targetMove == "") {
        return false;
    }

    if (squareName == sourceOfSan(targetMove)) {
        return true;
    } else {
        highlightSquareRed(squareName);
        return false;
    }
});

onMoveAttempted(function (san) {
    if (targetMove != "" && san == targetMove) {
        nextDelayed();
        targetMove = "";
        return true;
    } else {
        return false;
    }
});

onNextClicked(function () {
    showNextButton(false);
    next();
});

function nextDelayed() {
    setTimeout(next, 400);
}

function next() {
    if (steps.length > 0) {
        //remove the first function from the array and call it
        steps.shift()();
    }
}

next();