9. 도전과제 - 천천히 등장하는 배경색 구현, 섹션에 도착시 3D 모델이 회전하도록 구현
#a {height: 3000px}
.cube_wrap .cube_box.side {transform: rotateY(90deg) scale(1.5);}
.cube_wrap .cube_box.upper_side {transform: rotateX(90deg) scale(1.1);}
.cube_wrap .cube_box.back {transform: rotateY(-180deg) scale(1.5);}
var parallax = function () {
var scrollHeight = document.querySelector("#a").offsetHeight;
var scrollRealHeight = scrollHeight - innerHeight;
var scrollPercent = winScrollTop / scrollRealHeight;
var opacityValue = Math.min(1, scrollPercent);
document.querySelector(".dim").style.opacity = opacityValue;
}