CodePlayer

function getRandomColor() {
var letters = "0123456789ABCDEF".split('');
var color = "#";
for (var i = 0; i < 6; i++) {
    color += letters[Math.round(Math.random() * 15)];
}  
    return color;
} 
var clickedTime; var createdTime; var reactionTime;
function makeBox() {
    var time = Math.random();
    time = time * 1000;
    
        setTimeout(function () {
        if (Math.random() > 0.6) {
            document.getElementById("box").style.borderRadius = "100px";
        } else if(Math.random() > 0.3){
            document.getElementById("box").style.borderRadius = "50px";
        } else {
            document.getElementById("box").style.borderRadius = "0px";
        }
        var top = Math.random();
            top = top * 350;
            var left = Math.random();
            left = left * 1000;
    
            document.getElementById("box").style.top = top + "px";
            document.getElementById("box").style.left = left + "px";
            document.getElementById("box").style.backgroundColor = getRandomColor();
            document.getElementById("box").style.display = "block";
            createdTime = Date.now();
        }, time);
    }
    
        document.getElementById("box").onclick = function () {
        clickedTime = Date.now();
        reactionTime = (clickedTime - createdTime) / 1000;
        document.getElementById("reactionTime").innerHTML = "Reaction Time is: " + reactionTime + "seconds";
        this.style.display = "none";
        makeBox();
    }
makeBox();