var btn = document.getElementById("btn");
var box = document.querySelector(".box");
console.log(box);
btn.onclick = function() {
    box.style.background = 'red';
    box.style.left = 200 + 'px';
}
// var a = document.getElementById("a");
var b = document.getElementById("b");
var c = document.getElementById("c");
var d = document.getElementById("d");

var a = document.querySelector(".list #a");
var changeBtn = document.querySelector(".changeBtn");
changeBtn.onclick = function() {
    a.style.background = 'red';
    b.style.background = 'yellow';
    c.style.background = 'blue';
    d.style.background = 'green';
}