$(document).on('click', '.round', function() {
    var score = 0;
    score++;
    $('#result').html(score);
        this.remove();
});

$(document).on('click', '.round', function() {
    var score = 0;
    ^^^^^^^^^^^^^^
    score++;
    $('#result').html(score);
        this.remove();
});

var score = 0;
$(document).on('click', '.round', function() {
    score++;
    $('#result').html(score);
        this.remove();
});