body {
    font-family: Lato, Helvetica Neue For Number, -apple-system, BlinkMacSystemFont, Segoe UI, Roboto, PingFang SC, Hiragino Sans GB, "Microsoft JhengHei", "MicrMicrosoft YaHei", Helvetica Neue, Helvetica, Arial, sans-serif;
    line-height: 1.75;
    color: #333;
    margin: 0;
    padding: 20px 16px;
    background: linear-gradient(180deg, #d8e0dc 0%, #c9d2cd 55%, #bdc7c1 100%);
}

.about-layout {
    max-width: 1260px;
    margin: 0 auto;
    display: grid;
    grid-template-columns: minmax(220px, 260px) minmax(0, 1fr);
    gap: 18px;
    align-items: start;
}

.toc-panel {
    position: sticky;
    top: 16px;
    max-height: calc(100vh - 32px);
    overflow: auto;
    padding: 14px 12px;
    background: rgba(241, 246, 243, .9);
    border: 1px solid rgba(94, 113, 104, .22);
    border-radius: 8px;
    box-shadow: 0 8px 18px rgba(27, 39, 35, .1);
}

.toc-title {
    margin: 0 0 8px;
    font-size: 1rem;
    font-weight: 700;
    color: #275842;
}

.toc-list {
    list-style: none;
    margin: 0;
    padding: 0;
}

.toc-item+.toc-item {
    margin-top: 4px;
}

.toc-item.is-sub {
    padding-left: 14px;
}

.toc-link {
    display: block;
    padding: 4px 6px;
    border-radius: 6px;
    color: #25567b;
    font-size: .95rem;
    line-height: 1.35;
    text-decoration: none;
}

.toc-link:hover {
    background: rgba(34, 85, 124, .12);
    text-decoration: none;
}

.page-shell {
    max-width: none;
    margin: 0;
    width: 100%;
    padding: 28px 32px;
    background: rgba(248, 251, 249, .93);
    border-radius: 8px;
    border: 1px solid rgba(94, 113, 104, .22);
    box-shadow: 0 10px 24px rgba(27, 39, 35, .12);
}

h1 {
    text-align: center;
    font-size: 36px;
    font-weight: bold;
    margin-bottom: 30px;
}

h2 {
    font-size: 28px;
    color: #007BFF;
    margin-top: 40px;
    border-bottom: 2px solid #007BFF;
    padding-bottom: 10px;
}

h3 {
    font-size: 22px;
    margin-top: 30px;
    color: #0056b3;
}

p,
ul {
    margin-left: 20px;
}

ul {
    list-style-type: square;
}

a {
    color: #007BFF;
    text-decoration: none;
}

a:hover {
    text-decoration: underline;
}

.lang-switch {
    display: flex;
    gap: 2px;
    width: fit-content;
    margin: 0 0 0 auto;
    padding: 3px;
    background: rgba(94, 113, 104, .12);
    border: 1px solid rgba(94, 113, 104, .22);
    border-radius: 999px;
    font-size: .85rem;
    line-height: 1.2;
}

.lang-option {
    padding: 5px 14px;
    border-radius: 999px;
    color: #4a5a53;
    transition: background-color .15s ease, color .15s ease;
}

a.lang-option:hover,
a.lang-option:focus-visible {
    border-radius: 999px;
    background: rgba(34, 85, 124, .12);
    color: #25567b;
    text-decoration: none;
}

.lang-option.is-active {
    background: #fff;
    color: #275842;
    font-weight: 700;
    box-shadow: 0 1px 3px rgba(27, 39, 35, .18);
}

.contact-info {
    text-align: center;
    margin-bottom: 50px;
}

.contact-info a {
    margin: 0 10px;
}

.section {
    margin-bottom: 40px;
}

.sub-section {
    margin-top: 20px;
}

.bold {
    font-weight: bold;
}

#about-content h2,
#about-content h3 {
    scroll-margin-top: 16px;
}

@media screen and (max-width: 1024px) {
    .about-layout {
        grid-template-columns: 1fr;
        gap: 12px;
    }

    .toc-panel {
        position: static;
        max-height: none;
    }

    .toc-list {
        display: grid;
        grid-template-columns: repeat(2, minmax(0, 1fr));
        gap: 4px 10px;
    }
}

@media screen and (max-width: 768px) {
    .toc-panel {
        display: none;
    }

    .page-shell {
        padding: 20px 16px;
    }

    .toc-list {
        grid-template-columns: 1fr;
    }

    h1 {
        font-size: 30px;
    }

    h2 {
        font-size: 24px;
    }

    h3 {
        font-size: 20px;
    }

    p,
    ul {
        margin-left: 12px;
    }
}