.research-toc {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 2rem;
    padding: 2rem 0;
    border-bottom: 1px solid var(--line);
}
.research-toc ol,
.research-rail ol {
    list-style: none;
    margin: 0;
    padding: 0;
}
.research-toc a {
    display: flex;
    align-items: center;
    gap: 1rem;
    min-height: 44px;
    text-decoration: none;
    border-top: 1px solid var(--line);
    color: var(--soft);
}
.research-toc span {
    font: 0.8rem var(--mono);
    color: var(--accent);
}
.research-reading-layout {
    display: grid;
    grid-template-columns: minmax(0, 1fr) 170px;
    gap: 3rem;
}
.research-rail-track {
    grid-column: 2;
    grid-row: 1;
    min-width: 0;
}
.research-body {
    grid-column: 1;
    grid-row: 1;
    min-width: 0;
}
.research-rail {
    position: sticky;
    top: 2rem;
    padding-top: 2rem;
    font: 0.78rem/1.5 var(--mono);
}
.research-rail p {
    color: var(--accent);
    margin: 0 0 1rem;
}
.research-rail a {
    display: flex;
    align-items: center;
    min-height: 44px;
    padding: 0.5rem 0 0.5rem 1rem;
    border-left: 2px solid var(--line);
    color: var(--soft);
    text-decoration: none;
    transition:
        color 0.15s,
        border-color 0.15s;
}
.research-rail a[aria-current="location"] {
    border-color: var(--accent);
    color: var(--ink);
    font-weight: 500;
}
.research-toc a[aria-current="location"] {
    color: var(--accent);
}
.research-section {
    scroll-margin-top: 2rem;
}
.research-body .feature {
    gap: 2rem;
    grid-template-columns: minmax(0, 1fr) minmax(180px, 0.55fr);
}
.research-body .two-col {
    gap: 2rem;
}
@media (max-width: 1000px) {
    .research-reading-layout {
        gap: 1.5rem;
        grid-template-columns: minmax(0, 1fr) 150px;
    }
    .research-body .feature,
    .research-body .two-col,
    .research-body .image-story {
        grid-template-columns: 1fr;
    }
}
@media (max-width: 650px) {
    .research-toc {
        grid-template-columns: 1fr;
        gap: 1rem;
    }
    .research-reading-layout {
        display: block;
    }
    .research-rail-track {
        position: sticky;
        top: 0;
        z-index: 5;
        background: var(--paper);
        border-bottom: 1px solid var(--line);
    }
    .research-rail {
        position: static;
        padding: 0.5rem 0;
    }
    .research-rail p {
        margin: 0;
        font-size: 0.7rem;
    }
    .research-rail ol {
        display: flex;
        overflow-x: auto;
        gap: 0.75rem;
    }
    .research-rail li {
        flex: 0 0 auto;
    }
    .research-rail a {
        border-left: 0;
        border-bottom: 2px solid var(--line);
        padding: 0.4rem 0.1rem;
    }
    .research-section {
        scroll-margin-top: 100px;
    }
}