var startButton = document.querySelector('.start-button');
startButton.addEventListener("click", movement);

function movement() {
function markup(i) {
    return function () {
        console.log(i);
        markupLeft[i].classList.toggle('markup-lighting');
    }
}
for(var i = 0;i<markupLeft.length; i++) {
setTimeout(markup(i), i * 100);
}
}