* {
	margin: 0;
	padding: 0;
	box-sizing: border-box;
	font-family: sans-serif;
}

ul,
li {
	padding: 0;
	margin: 0;
	list-style: none;
}

a {
	text-decoration: none;
	color: #000;
}

.iconnav i {
	color: #fff;
	font-size: 20px;
	display: none;
}

.topnav {
	background-color: #000;
	position: relative;
}

.topnav ul {
	display: flex;
	justify-content: center;
	align-items: center;
}

.topnav a {
	display: block;
	padding: 10px 20px;
	color: #fff;
}

.topnav a:hover {
	background-color: aqua;
}

@media (max-width: 600px) {
	.topnav ul {
		flex-direction: column;
		justify-content: flex-start;
	}

	.topnav li {
		width: 100%;
		text-align: left;
	}

	.iconnav {
		position: absolute;
		top: 0;
		right: 0;
		display: block;
		padding: 10px;
	}

	.iconnav i {
		display: block;
	}
}

.wrapper {
	display: flex;
	/* kich hoat flex box*/
	flex-flow: row wrap;
	font-weight: bold;
	text-align: center;
}

.wrapper>* {
	padding: 10px;
	flex: 1 100%;
	/* cho tất cả phần tử bên trong có độ dà i 100% và tỉ lệ chiếm không gian trống là như nhau*/
}

.header-flex-2 {
	background: tomato;
}

.footer-flex-2 {
	background: lightgreen;
	order: 4;
}

.main {
	text-align: left;
	background: deepskyblue;
	flex: 3 0px;
	order: 2;
}

.aside {
	flex: 1 0 0;
}

.aside-1 {
	background: gold;
	order: 1;
}

.aside-2 {
	background: hotpink;
	order: 3;
}

.container-img {
	display: flex;
	justify-content: center;
	align-items: center;
}

.img-responsive {
	max-width: 100%;
	height: auto;
}

@media (max-width: 1200px) {
	.main {
		order: 1;
		flex: 1 100%
	}
}

@media (max-width: 600px) {
	body {
		font-size: 20px;
	}

	.wrapper {
		flex-direction: column;
	}

	.main {
		order: 1;
	}

	.aside-1 {
		order: 2;
	}
}