body{
    background: antiquewhite;
    margin-left: 1em;
    margin-right: 1em;
}

h1{
    color: saddlebrown;
    text-align: center;
    border-radius: 15px;
}

h2{
    color: cadetblue;
    margin-top: 1.5em;
}

*,
*:before,
*:after {
    -webkit-box-sizing: inherit;
    box-sizing: inherit;
}

html {
    -webkit-box-sizing: border-box;
    box-sizing: border-box;
    font-size: 62.5%;/*rem算出をしやすくするために*/
}

.btn,
a.btn,
button.btn {
    font-size: 1.6rem;
    font-weight: 700;
    line-height: 1.5;
    position: relative;
    display: inline-block;
    padding: 1rem 4rem;
    cursor: pointer;
    -webkit-user-select: none;
    -moz-user-select: none;
    -ms-user-select: none;
    user-select: none;
    -webkit-transition: all 0.3s;
    transition: all 0.3s;
    text-align: center;
    vertical-align: middle;
    text-decoration: none;
    letter-spacing: 0.1em;
    color: #212529;
    border-radius: 0.5rem;
    margin: 0.5em;
}

.btn--orange,
a.btn--orange {
    color: #fff;
    background-color: salmon;
}
.btn--orange:hover,
a.btn--orange:hover {
    color: #fff;
    background: tomato;
}

a.btn--radius {
    border-radius: 100vh;
}