/* Modern Academic Theme */
:root {
    --color-primary: #8c1515;       /* Stanford cardinal */
    --color-primary-dark: #6e1010;
    --color-primary-light: #f5e6e6;
    --color-accent: #2e5090;        /* Complementary deep blue for links */
    --color-text: #1f2937;          /* Near black */
    --color-text-secondary: #6b7280; /* Medium gray */
    --color-text-light: #9ca3af;    /* Light gray */
    --color-border: #e5e7eb;
    --color-bg: #ffffff;
    --color-bg-page: #f7f5f2;       /* Warm parchment */
    --color-bg-subtle: #faf8f5;
    --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
    --font-serif: 'Merriweather', Georgia, serif;
    --max-width: 960px;
    --content-padding: 0 4rem 4rem 4rem;
}

/* ─── Base ─── */
body {
    font-family: var(--font-sans);
    line-height: 1.7;
    color: var(--color-text);
    background-color: var(--color-bg-page);
    font-size: 14px;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

/* ─── Typography ─── */
h1, h2, h3 {
    font-family: var(--font-sans);
    color: var(--color-text);
    border-bottom: none;
    padding-bottom: 0;
    font-weight: 700;
    letter-spacing: -0.02em;
}

h1 {
    font-size: 1.6rem;
    margin-bottom: 0.25rem;
    margin-top: 0;
    padding-top: 0;
}

#toptitle {
    margin: 0;
    padding: 0.5rem 0 0.25rem 0;
}

#toptitle h1 {
    margin: 0;
    padding: 0;
}

h2 {
    font-size: 1.1rem;
    margin-top: 2rem;
    margin-bottom: 0.75rem;
    padding-bottom: 0.4rem;
    border-bottom: 2px solid var(--color-primary);
    display: inline-block;
    color: var(--color-text);
    letter-spacing: -0.01em;
}

h3 {
    font-size: 0.95rem;
    color: var(--color-text);
}

a {
    color: var(--color-accent);
    text-decoration: none;
    transition: color 0.15s;
}

a:hover {
    color: var(--color-primary);
    text-decoration: underline;
}

/* ─── Navigation ─── */
#layout-menu {
    background: var(--color-bg);
    box-shadow: 0 1px 8px rgba(0,0,0,0.06);
    position: sticky;
    top: 0;
    z-index: 100;
}

.menu-item {
    display: inline-block;
}

.menu-item a {
    font-family: var(--font-sans);
    font-weight: 500;
    font-size: 0.9rem;
    transition: color 0.15s ease;
    display: block;
    padding: 0.9rem 1.4rem;
    color: var(--color-text-secondary);
    border-bottom: 2px solid transparent;
    letter-spacing: 0;
}

.menu-item a:hover {
    color: var(--color-primary);
    background-color: transparent;
    text-decoration: none;
    border-bottom-color: var(--color-primary);
}

.menu-item a.current {
    color: var(--color-primary);
    font-weight: 600;
    border-bottom: 2px solid var(--color-primary);
}

/* ─── Contact Links (Simon Du style) ─── */
.contact-links {
    margin-top: 0.75rem;
    font-size: 0.88rem;
    line-height: 1.8;
    color: var(--color-text);
}

.contact-links a {
    color: var(--color-accent);
    font-weight: 500;
}

.contact-links a:hover {
    color: var(--color-primary);
}

/* ─── Content Area ─── */
#layout-content {
    padding: var(--content-padding);
    background-color: var(--color-bg);
    border-radius: 0;
    box-shadow: none;
    border: none;
    box-sizing: border-box;
}

/* ─── Profile Section ─── */
.profile-section {
    display: flex;
    align-items: flex-start;
    margin-bottom: 1.5rem;
    padding-bottom: 0;
    border-bottom: none;
    gap: 2rem;
}

.profile-image {
    border-radius: 8px;
    box-shadow: 0 4px 16px rgba(0,0,0,0.08);
    max-width: 140px;
    height: auto;
    border: none;
    outline: none;
    flex-shrink: 0;
}

.profile-section p {
    margin: 0.25rem 0 0 0;
    font-size: 0.93rem;
    line-height: 1.75;
    color: var(--color-text);
}

/* ─── Social Links (legacy) ─── */
.social-links {
    margin-top: 0.75rem;
}

.social-links a {
    text-decoration: none;
    font-weight: 500;
    font-size: 0.95rem;
    color: var(--color-accent);
    display: inline;
}

.social-links a:hover {
    color: var(--color-primary);
    text-decoration: underline;
}

/* ─── News Section ─── */
.news-section {
    background-color: transparent;
    padding: 0;
    margin: 0.5rem 0 1.5rem 0;
    border-left: none;
    padding-left: 0;
}

.news-item {
    margin-bottom: 0;
    padding: 0.65rem 0;
    border-bottom: 1px solid var(--color-border);
    font-size: 0.92rem;
    line-height: 1.65;
}

.news-item:last-child {
    border-bottom: none;
    padding-bottom: 0;
}

.news-date {
    font-weight: 600;
    color: var(--color-primary);
    margin-right: 0.5rem;
    font-family: var(--font-sans);
    font-size: 0.85rem;
}

.badge {
    display: inline-block;
    padding: 0.1rem 0.45rem;
    background-color: var(--color-primary-light);
    color: var(--color-primary);
    border-radius: 4px;
    font-size: 0.7rem;
    font-weight: 600;
    margin-left: 0.4rem;
    text-transform: uppercase;
    letter-spacing: 0.04em;
}

.new-badge {
    background-color: var(--color-primary-light);
    color: var(--color-primary);
}

/* ─── Publications (Home - with images) ─── */
.publication-list {
    margin-top: 1rem;
}

.publication-item {
    margin-bottom: 1.75rem;
    padding: 1.5rem;
    background-color: var(--color-bg);
    border: 1px solid var(--color-border);
    border-radius: 8px;
    border-left: none;
    transition: box-shadow 0.2s ease;
}

.publication-item:hover {
    box-shadow: 0 2px 12px rgba(0,0,0,0.06);
}

.imgtable {
    margin-bottom: 0;
    width: 100%;
}

.imgtable td {
    vertical-align: top;
    padding: 0;
    border: none;
}

.imgtable td:first-child {
    width: 280px;
    padding-right: 1.5rem;
}

.imgtable img {
    border-radius: 6px;
    box-shadow: none;
    max-width: 260px;
    height: auto;
    border: 1px solid var(--color-border);
}

.imgtable p {
    margin: 0 0 0.5rem 0;
}

.imgtable a {
    font-family: var(--font-sans);
    font-weight: 600;
    font-size: 0.93rem;
    color: var(--color-text);
    line-height: 1.5;
}

.imgtable a:hover {
    color: var(--color-primary);
}

/* ─── Publications (List page) ─── */
ul.publication-list {
    list-style: none;
    padding: 0;
    margin-top: 1rem;
}

li.publication-item {
    margin-bottom: 0;
    padding: 1.15rem 0;
    background: none;
    border: none;
    border-bottom: 1px solid var(--color-border);
    border-radius: 0;
}

li.publication-item:hover {
    box-shadow: none;
}

li.publication-item:last-child {
    border-bottom: none;
}

li.publication-item > a {
    font-weight: 600;
    font-size: 0.93rem;
    color: var(--color-text);
    line-height: 1.5;
}

li.publication-item > a:hover {
    color: var(--color-primary);
}

.publication-authors {
    margin: 0.3rem 0 0.15rem;
    font-size: 0.85rem;
    color: var(--color-text-secondary);
}

.publication-venue {
    font-style: italic;
    color: var(--color-text-secondary);
    font-size: 0.83rem;
}

/* ─── Notes page ─── */
.notes-list {
    list-style-type: none;
    padding: 0;
    margin-top: 1rem;
}

.note-item {
    background-color: transparent;
    padding: 1rem 0;
    margin-bottom: 0;
    border: none;
    border-bottom: 1px solid var(--color-border);
    border-left: none;
    border-radius: 0;
}

.note-item:last-child {
    border-bottom: none;
}

.note-item:hover {
    border-left-color: transparent;
}

.note-item > a {
    font-weight: 600;
    font-size: 0.93rem;
    color: var(--color-text);
}

.note-item > a:hover {
    color: var(--color-primary);
}

.chapter-links {
    margin-top: 0.6rem;
    display: flex;
    flex-wrap: wrap;
    gap: 0.4rem;
}

.chapter-links a {
    display: inline-block;
    padding: 0.25rem 0.65rem;
    background-color: var(--color-bg-subtle);
    border: 1px solid var(--color-border);
    border-radius: 5px;
    font-size: 0.83rem;
    transition: all 0.15s;
    color: var(--color-text-secondary);
}

.chapter-links a:hover {
    background-color: var(--color-accent);
    color: white;
    text-decoration: none;
    border-color: var(--color-accent);
}

.new-badge {
    background-color: var(--color-primary-light);
    color: var(--color-primary);
}

/* ─── Publication action links ─── */
.publication-item a[style*="display: inline-block"] {
    font-family: var(--font-sans) !important;
    font-weight: 500 !important;
    font-size: 0.83rem !important;
    color: var(--color-text-secondary) !important;
    padding: 0.25rem 0.6rem;
    border: 1px solid var(--color-border);
    border-radius: 5px;
    margin-right: 0.3rem;
    margin-top: 0.5rem;
    background-color: var(--color-bg-subtle);
    transition: all 0.15s ease;
}

.publication-item a[style*="display: inline-block"]:hover {
    background-color: var(--color-primary);
    color: white !important;
    border-color: var(--color-primary);
    text-decoration: none;
}

.imgtable td:last-child {
    font-size: 0.92rem;
    line-height: 1.65;
}

/* ─── About paragraph ─── */
#layout-content > p {
    text-align: left;
    line-height: 1.8;
    color: var(--color-text);
}

/* ─── Contact section ─── */
h2 + p:last-of-type {
    font-size: 1rem;
    color: var(--color-text-secondary);
}

/* ─── Sudoku widget ─── */
.sudoku-section {
    background: var(--color-bg-subtle);
    border-radius: 8px;
    padding: 1.25rem;
    margin: 2rem 0;
    border: 1px solid var(--color-border);
}

.sdk-wrap {
    max-width: 720px;
}

.sdk-header {
    display: flex;
    align-items: center;
    gap: 12px;
    font-weight: 600;
    color: var(--color-text);
    margin-bottom: 10px;
    font-family: var(--font-sans);
}
.sdk-header .sdk-best { color: #059669; font-weight: 500; }
.sdk-header .sdk-restart {
    margin-left: auto;
    background: var(--color-bg);
    border: 1px solid var(--color-border);
    color: var(--color-text);
    padding: 6px 10px;
    border-radius: 5px;
    cursor: pointer;
    font-size: 0.85rem;
}
.sdk-header .sdk-restart:hover { background: var(--color-bg-subtle); }

.sdk-body { display: flex; gap: 16px; align-items: flex-start; }

.sdk-grid {
    display: grid;
    grid-template-columns: repeat(6, 54px);
    grid-auto-rows: 54px;
    gap: 0;
    background: var(--color-bg);
    border-radius: 6px;
    padding: 8px;
    border: 2px solid var(--color-text);
}

.sdk-row { display: contents; }

.sdk-cell {
    display: flex;
    align-items: center;
    justify-content: center;
    font-family: var(--font-sans);
    font-size: 20px;
    width: 54px; height: 54px;
    border: 1px solid var(--color-border);
    color: var(--color-text);
    background: var(--color-bg);
    user-select: none;
}
.sdk-cell.fixed { background: var(--color-bg-subtle); font-weight: 700; color: var(--color-text); }
.sdk-cell.editable { cursor: pointer; }
.sdk-cell.selected { outline: 2px solid var(--color-primary); outline-offset: -2px; }
.sdk-cell.conflict { background: #fef2f2; color: #dc2626; }
.sdk-cell.notes { font-size: 12px; color: var(--color-text-light); }

.sdk-cell.thick-top { border-top: 3px solid #6b7280; }
.sdk-cell.thick-left { border-left: 3px solid #6b7280; }
.sdk-cell.thick-bottom { border-bottom: 3px solid #6b7280; }
.sdk-cell.thick-right { border-right: 3px solid #6b7280; }

.sdk-controls { display: flex; flex-direction: column; gap: 10px; }
.sdk-keypad { display: grid; grid-template-columns: repeat(3, 64px); gap: 8px; }
.sdk-btn {
    background: var(--color-bg);
    border: 1px solid var(--color-border);
    border-radius: 5px;
    padding: 10px 0;
    font-weight: 600;
    cursor: pointer;
    transition: all .15s ease;
    font-family: var(--font-sans);
}
.sdk-btn:hover { background: var(--color-bg-subtle); }
.sdk-btn.secondary { background: var(--color-bg-subtle); }

.sdk-submit {
    margin-top: 8px;
    background: var(--color-primary);
    color: #fff;
    border: none;
    padding: 12px 16px;
    border-radius: 5px;
    font-weight: 600;
    cursor: pointer;
    font-family: var(--font-sans);
}
.sdk-submit:hover { background: var(--color-primary-dark); }

.sdk-footnote { margin-top: 8px; color: var(--color-text-light); font-size: 12px; }

/* ─── Responsive ─── */
@media screen and (max-width: 768px) {
    #tlayout {
        display: block;
        width: 100%;
    }

    #layout-menu, #layout-content {
        display: block;
        width: 100%;
        max-width: 100%;
        float: none;
        box-sizing: border-box;
    }

    #layout-menu {
        padding: 0;
        border: none;
        border-bottom: none;
        margin-bottom: 0;
        text-align: center;
        background-color: var(--color-bg);
        overflow-x: auto;
        white-space: nowrap;
        -webkit-overflow-scrolling: touch;
    }

    .menu-item {
        display: inline-block;
        margin: 0;
    }

    .menu-item a {
        padding: 0.7rem 1rem;
        font-size: 0.85rem;
    }

    #layout-content {
        padding: 1.5rem;
        border: none;
    }

    .profile-section {
        flex-direction: column;
        align-items: center;
        text-align: center;
        padding-bottom: 1.5rem;
    }

    .profile-section > div {
        display: flex;
        flex-direction: column;
        align-items: center;
    }

    .profile-image {
        margin-bottom: 1.25rem;
    }

    #toptitle {
        text-align: center;
    }

    .social-links {
        justify-content: center;
        flex-wrap: wrap;
    }

    .imgtable, .imgtable tr, .imgtable td {
        display: block;
        width: 100%;
        text-align: center;
    }

    .imgtable td:first-child {
        width: 100%;
        padding-right: 0;
        padding-bottom: 1rem;
        display: flex;
        justify-content: center;
    }

    .imgtable img {
        max-width: 100%;
        height: auto;
    }

    .imgtable td:last-child p {
        text-align: center;
    }

    h1 {
        font-size: 1.4rem;
        text-align: center;
    }

    h2 {
        font-size: 1rem;
        display: block;
    }

    #layout-content {
        text-align: center;
    }

    #layout-content > p {
        text-align: left;
    }

    .news-section {
        text-align: left;
    }

    .sdk-body { flex-direction: column; align-items: center; }
    .sdk-grid { grid-template-columns: repeat(6, 44px); grid-auto-rows: 44px; }
    .sdk-cell { width: 44px; height: 44px; font-size: 18px; }
    .sdk-keypad { grid-template-columns: repeat(3, 64px); }
}

@media screen and (max-width: 480px) {
    .menu-item a {
        padding: 0.6rem 0.7rem;
        font-size: 0.82rem;
    }

    #layout-content {
        padding: 1rem;
    }

    .publication-item {
        padding: 1rem;
    }

    h1 {
        font-size: 1.25rem;
    }

    h2 {
        font-size: 0.95rem;
    }

    .profile-image {
        max-width: 140px;
    }

    .sdk-grid { grid-template-columns: repeat(6, 38px); grid-auto-rows: 38px; }
    .sdk-cell { width: 38px; height: 38px; font-size: 16px; }
    .sdk-keypad { grid-template-columns: repeat(3, 56px); }
}

/* Subgrid completion animation */
.sdk-finish-pop {
    animation: sdkPop 0.6s ease both;
}

@keyframes sdkPop {
    0% { transform: scale(1); background: #dbeafe; }
    35% { transform: scale(1.06); background: #bbf7d0; }
    100% { transform: scale(1); background: #fff; }
}

/* ─── Research page ─── */
.research-intro {
    text-align: left;
    max-width: 46rem;
    margin: 0.9rem 0 0;
    font-size: 0.95rem;
    line-height: 1.85;
    color: var(--color-text);
}

/* Understand · Generalize · Discover — three parallel directions */
.research-arc {
    display: grid;
    grid-template-columns: repeat(3, minmax(0, 1fr));
    gap: 0.5rem 1.5rem;
    max-width: 38rem;
    margin: 2.25rem auto 0;
    padding: 1.4rem 0;
    border-top: 1px solid var(--color-border);
    border-bottom: 1px solid var(--color-border);
}

.research-arc-item {
    text-align: center;
    text-decoration: none;
}

.research-arc-item:hover {
    text-decoration: none;
}

.research-arc-label {
    display: block;
    font-size: 0.82rem;
    font-weight: 600;
    letter-spacing: 0.16em;
    text-transform: uppercase;
    color: var(--color-primary);
}

.research-arc-sub {
    display: block;
    margin-top: 0.3rem;
    font-size: 0.76rem;
    line-height: 1.45;
    color: var(--color-text-secondary);
}

.research-arc-item:hover .research-arc-sub {
    color: var(--color-primary);
}

/* Alternating text / figure sections.
   The heading owns its own grid row so the figure aligns against the body
   text rather than against the eyebrow, and centres within it. */
.research-direction {
    display: grid;
    grid-template-columns: 1fr 40%;
    grid-template-areas:
        "head ."
        "body fig";
    column-gap: 3rem;
    padding: 3rem 0;
    border-bottom: 1px solid var(--color-border);
    scroll-margin-top: 4rem;
}

.research-direction:last-of-type {
    border-bottom: none;
    padding-bottom: 1rem;
}

.research-direction--reverse {
    grid-template-columns: 40% 1fr;
    grid-template-areas:
        ".   head"
        "fig body";
}

.research-direction-head {
    grid-area: head;
    text-align: left;
}

.research-direction-content {
    grid-area: body;
    min-width: 0;
    text-align: left;
}

.research-direction-figure {
    grid-area: fig;
    align-self: center;
    min-width: 0;
    margin: 0;
}

.research-direction-content p {
    font-size: 0.93rem;
    line-height: 1.8;
}

.research-direction h2 {
    margin-top: 0.4rem;
    margin-bottom: 1rem;
    line-height: 1.4;
}

.research-eyebrow {
    margin: 0;
    font-size: 0.72rem;
    font-weight: 600;
    letter-spacing: 0.14em;
    text-transform: uppercase;
    color: var(--color-text-light);
}

.research-num {
    color: var(--color-primary);
    margin-right: 0.5rem;
}

/* Links to my own work */
.research-related {
    margin-top: 1.5rem;
    text-align: left;
}

.research-related-label {
    display: block;
    margin-bottom: 0.35rem;
    font-size: 0.7rem;
    font-weight: 600;
    letter-spacing: 0.12em;
    text-transform: uppercase;
    color: var(--color-text-light);
}

.research-related ul {
    list-style: none;
    padding: 0;
    margin: 0;
}

.research-related li {
    padding: 0.28rem 0;
    font-size: 0.85rem;
    line-height: 1.6;
}

.research-related li a {
    font-weight: 500;
}

.research-related-venue {
    display: block;
    font-size: 0.78rem;
    font-style: italic;
    color: var(--color-text-light);
}

/* Conceptual figures */
.research-direction-figure img {
    display: block;
    width: 100%;
    height: auto;
    box-sizing: border-box;
    padding: 0.75rem;
    background-color: var(--color-bg);
    border: 1px solid var(--color-border);
    border-radius: 6px;
}

.research-caption {
    margin-top: 0.65rem;
    text-align: left;
    font-size: 0.78rem;
    line-height: 1.55;
    color: var(--color-text-light);
}

@media screen and (max-width: 768px) {
    .research-direction,
    .research-direction--reverse {
        grid-template-columns: minmax(0, 1fr);
        grid-template-areas:
            "head"
            "body"
            "fig";
        padding: 2.25rem 0;
    }

    .research-direction-figure {
        align-self: stretch;
        margin-top: 1.75rem;
    }

    .research-arc {
        gap: 0.5rem 1rem;
    }
}

@media screen and (max-width: 480px) {
    .research-arc {
        gap: 0.4rem 0.6rem;
    }

    .research-arc-label {
        font-size: 0.74rem;
        letter-spacing: 0.08em;
    }

    .research-arc-sub {
        font-size: 0.71rem;
    }
}