@charset "UTF-8";

body {
font-family: sans-serif;
background-color: #b0e0e6;
font-size: 16px;
line-height: 1.8;
color:#252525;
}

.container {
margin: 0 auto 0 auto;
max-width: 900px;
background-color: #fff;
}

header{
background-color:#00bfff;
padding: 20px;
}

footer{
background-color:#00bfff;
padding: 10px;
text-align: center;
}

section {
display: flex;
flex-flow: column;
}

main {
padding: 20px;
}

aside {
padding: 20px;
}

@media only screen and (min-width: 768px) {
section {
flex-flow: row;
}
main {
flex: 1 1 auto;
order: 2;
}
aside {
flex: 0 0 200px;
order: 1;
}
}

h1 {
text-align: center;
}

h2 {
margin-top: 20px;
padding-bottom: 5px;
border-bottom: 2px solid #87ceeb;
}

h3 {
color:deepskyblue;
text-align: center;
}

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


.btn {
margin: 0;
padding: 0;
list-style-type: none;
}
.btn li a {
display: block;
background: #ff6347;
padding: 10px 8px;
color: #fff;
text-decoration: none;
text-align: center;
margin-bottom: 15px;
border-radius: 10px;
}
.btn li a:hover {
background: #b22222;
color: #fff;
}

.naka{
text-align: center;
} 

#page_top{
width: 100px;
height: 40px;
position: fixed;
right: 0;
bottom: 10px;
background: #007ab5;
opacity: 0.6;
}
#page_top a{
position: relative;
display: block;
width: 100px;
height: 40px;
text-decoration: none;
}

#page_top a::after{
content: '↑ PAGE TOP';
font-size: 14px;
font-weight: bold;
color: #fff;
position: absolute;
top: 10px;
bottom: 0;
right: 0;
left: 0;
margin: auto;
text-align: center;
}

html{
scroll-behavior: smooth;
}