@media screen and (min-width:0px){
  /*0px以上で適用する内容*/
}

@media screen and (min-width:300px){
  /*300px以上で適用する内容*/
}

@media screen and (min-width:769px){
	#contents{
		display: -webkit-flex;
		display: flex;
		-webkit-flex-direction: row-reverse;
		flex-direction: row-reverse;
	}
	main{
		width: 100%;
		padding-left: 300px;
		margin-left: auto;
	}
	aside{
		width: 100%;
    	max-width: 300px;
	}
}