@media (max-width: 641px) {
    .login_link{width: 100%;}
}
.page-header{background: linear-gradient(rgba(24, 29, 56, .7), rgba(24, 29, 56, .7)), url(../img/front.jpg);background-position: center center;
    background-repeat: no-repeat;
    background-size: cover;}
.wrapper{display: flex;height: auto;min-height: 100%;flex-direction: column;}
html,body{height: 100%;}
main{flex: 1 1 auto}
.login{max-width: 400px;margin: 30px auto;}
.register_link{text-align: center;display: block;margin-top: 30px;text-decoration: underline}