body {
	font-family: Arial, sans-serif;
	margin: 0;
	padding: 0;
	background-color: #f4f4f4;
}
.container {
	width: 80%;
	margin: auto;
	overflow: hidden;
}
header {
	background: #0186ba;
	color: #ffffff;
	padding-top: 30px;
	min-height: 70px;
	border-bottom: #e8491d 3px solid;
}
header a {
	color: #ffffff;
	text-decoration: none;
	text-transform: uppercase;
	font-size: 16px;
}
header ul {
	padding: 0;
	list-style: none;
}
header li {
	float: left;
	display: inline;
	padding: 0 20px 0 20px;
}
header #branding {
	float: left;
}
header #branding h1 {
	margin: 0;
}
header nav {
	float: right;
	margin-top: 10px;
}
.main-content {
	display: flex;
	margin-top: 20px;
}
.topics {
	flex: 1;
	background: #ffffff;
	padding: 20px;
	margin-right: 20px;
	box-shadow: 0 0 10px rgba(0, 0, 0, 0.1);
}
.topics h2 {
	margin-top: 0;
}
.topics ul {
	list-style: none;
	padding: 0;
}
.topics li {
	background: #e4e4e4;
	margin-bottom: 10px;
	padding: 10px;
	border-radius: 5px;
}
.topics li a {
	text-decoration: none;
	color: #000;
}
.posts {
	flex: 3;
}
.post {
	background: #ffffff;
	padding: 20px;
	margin-bottom: 20px;
	box-shadow: 0 0 10px rgba(0, 0, 0, 0.1);
}
.post img {
	max-width: 100%;
}
.post h2 {
	margin-top: 0;
}
@media (max-width: 600px) {
	.main-content {
		flex-direction: column;
	}
	.topics {
		margin: 0 0 20px 0;
	}
}
/* トップへ戻るボタンのスタイル */
#back-to-top {
	display: none;
	position: fixed;
	bottom: 30px;
	right: 30px;
	z-index: 100;
	background: #e8491d;
	color: #ffffff;
	padding: 10px 15px;
	border-radius: 5px;
	text-align: center;
	cursor: pointer;
}