html, body {
    height: 100%;
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    background: #fff;
    font-family: Arial, sans-serif;
}
body {
    position: fixed;
    padding-top: 100px;
    height: 100vh;
    display: flex;
    flex-direction: column;
    width: 100%;
}
header {
    font-family: 'Courier New', Courier, monospace;
    background: #111;
    color: #87cefa;
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 0 1.5rem;
    position: fixed;
    width: calc(100% - 3rem);
    height: 100px;
    top: 0;
    z-index: 1000;
}
.title {
    font-weight: bold;
    color: #87cefa;
    .maintitle {
        font-size: 3rem;
        letter-spacing: 1px;
    }
    .subtitle {
        padding-left: 10px;
        font-size: 1rem;
        letter-spacing: 10px;
    }
}
.menu-icon {
    width: 32px;
    height: 32px;
    display: flex;
    flex-direction: column;
    justify-content: center;
    cursor: pointer;
}
.menu-icon span {
    display: block;
    height: 4px;
    width: 100%;
    background: #87cefa;
    margin: 4px 0;
    border-radius: 2px;
    transition: 0.3s;
}
nav {
    position: fixed;
    right: 0;
    background: #111;
    width: 220px;
    max-width: 80vw;
    box-shadow: -2px 0 8px rgba(0,0,0,0.1);
    transform: translateX(100%);
    transition: transform 0.3s;
    z-index: 999;
}
nav.open {
    transform: translateX(0);
}
nav ul {
    list-style: none;
    margin: 0;
    padding: 1rem 0;
}
nav li {
    margin: 0;
    padding: 0;
}
nav a {
    display: block;
    padding: 1rem 2rem;
    color: #87cefa;
    text-decoration: none;
    font-size: 1.1rem;
    transition: background 0.2s;
}
nav a:hover {
    background: #222;
}
main {
    width: calc(100% - 2rem);
    flex: 1;
    padding: 0 1rem;
    margin: 0 auto;
    overflow-y: scroll;
}
section {
    padding-top: 2rem;
}
section h2 {
    color: #111;
    margin-top: 0;
}
@media (min-width: 900px) {
    section {
        width: 900px;
        margin: 0 auto;
    }
}
@media (max-width: 500px) {
    .title {
        font-size: 1.2rem;
    }
}