/* Reset */
* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

body {
    font-family: 'Inter', 'Pretendard', Arial, sans-serif;
    background: #181a1b;
    color: #e0e0e0;
    min-height: 100vh;
    margin: 24px;
}

header {
    background: linear-gradient(90deg, #232323 60%, #444 100%);
    color: #fff;
    padding: 24px 0 16px 0;
    text-align: center;
    font-size: 2rem;
    letter-spacing: 2px;
    font-weight: 700;
    box-shadow: 0 2px 8px rgba(40, 40, 40, 0.18);
    border-radius: 12px 12px 0 0;
}

nav {
    width: 220px;
    min-height: 100vh;
    background: #202124;
    padding: 32px 0 0 0;
    position: fixed;
    left: 24px;
    top: 24px;
    box-shadow: 2px 0 16px rgba(40, 40, 40, 0.12);
    z-index: 10;
    border-right: 1px solid #333;
    border-radius: 12px 0 0 12px;
}

nav h2 {
    color: #bbb;
    font-size: 1.2rem;
    margin-bottom: 24px;
    padding-left: 32px;
    font-weight: 600;
    letter-spacing: 1px;
}

nav ul {
    list-style: none;
    padding-left: 0;
}

nav a {
    color: #e0e0e0;
    text-decoration: none;
    display: flex;
    align-items: center;
    gap: 10px;
    padding: 12px 32px;
    margin: 6px 0;
    border-radius: 8px;
    font-size: 1.05rem;
    font-weight: 500;
    transition:
        background 0.18s cubic-bezier(.4, 0, .2, 1),
        color 0.18s cubic-bezier(.4, 0, .2, 1),
        transform 0.12s;
    position: relative;
    overflow: hidden;
}

nav a::before {
    content: '';
    display: block;
    position: absolute;
    left: 0;
    top: 0;
    bottom: 0;
    width: 4px;
    background: #888;
    opacity: 0;
    transition: opacity 0.2s;
    border-radius: 4px;
}

nav a:hover,
nav a.active {
    background: linear-gradient(90deg, #292929 70%, #4443 100%);
    color: #fff;
    transform: translateX(4px) scale(1.03);
}

nav a.active::before,
nav a:hover::before {
    opacity: 1;
}

main,
#content {
    margin-left: 264px;
    padding: 40px 32px 32px 32px;
    min-height: 100vh;
    background: #232323;
    border-radius: 0 0 16px 16px;
    box-shadow: 0 4px 24px rgba(40, 40, 40, 0.10);
}

h1,
h2,
h3 {
    font-weight: 700;
    color: #bbb;
    margin-bottom: 16px;
}

p {
    margin-bottom: 16px;
    line-height: 1.7;
    color: #e0e0e0;
}

iframe {
    border: none;
    margin: 24px 0;
    width: 100%;
    min-height: 400px;
    box-shadow: 0 2px 12px rgba(40, 40, 40, 0.10);
}

div.button-box {
    display: flex;
    gap: 12px;
    margin-bottom: 24px;
}

footer {
    text-align: center;
    padding: 18px 0;
    background: #202124;
    color: #bbb;
    font-size: 0.95rem;
    letter-spacing: 1px;
    margin-top: 40px;
    border-radius: 0 0 16px 16px;
    box-shadow: 0 -2px 8px rgba(40, 40, 40, 0.10);
}

@media (max-width: 900px) {
    body {
        margin: 0;
    }

    nav {
        width: 100%;
        min-height: unset;
        position: static;
        box-shadow: none;
        padding: 16px 0 0 0;
        border-right: none;
        border-radius: 12px 12px 0 0;
        left: 0;
        top: 0;
    }

    main,
    #content {
        width: 100%;
        margin-left: 0;
        padding: 24px 4vw 24px 4vw;
        border-radius: 0 0 16px 16px;
    }
}