Introduction to skewers

Code

//Please feel welcome to copy this code for your own creations.
fromFen("5k1r/p1p3pp/2bp1p1q/2n1p3/2P1P3/B1NP4/P1P1QPPP/1R3RK1 w k - 0 1");

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

steps.push(function() {
    info("Skewers are similar to pins, except in reverse.\
    <br>A skewer threatens a valuable piece, forcing it to move, and exposing another piece to attack.\
    <br>Play Rb8+ to skewer the opponent's king and rook.");

    targetMove = "Rb8+";
});

steps.push(function() {
   performMove("Kf7");
   nextDelayed();
});

steps.push(function() {
   info("You are now free to take the opponent's rook.");
   targetMove = "Rxh8";
});

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

steps.push(function() {
   fromFen("2Q5/1p4q1/p4k2/6p1/P3b3/6BP/5PP1/6K1 w - - 0 1");
   
   info("In \"Nigel Short vs. Rafael Vaganian, Barcelona World Cup (1989)\" skewers are used to capture the black queen.\
   <br>First we use our bishop to skewer the king and queen.");
   targetMove = "Be5+";
});

steps.push(function() {
   performMove("Kxe5");
   nextDelayed();
});

steps.push(function() {
    info("Now that the black king is not defending the queen anymore, we can skewer it with our queen");
    targetMove = "Qc3+";
});

steps.push(function() {
   performMove("Kf5"); 
   nextDelayed();
});

steps.push(function() {
    targetMove = "Qxg7";
});

steps.push(function() {
   info("Correct!");
   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();