/* ==================== CSS VARIABLES ==================== */
:root {
    --color-bg: #f2f6fc;
    --color-bg-alt: #e8f0f8;
    --color-text: #1a2333;
    --color-text-light: #3d5470;
    --color-text-muted: #7a93b0;

    --color-primary: #2563a8;
    --color-primary-hover: #1a4d8a;
    --color-accent-warm: #4a8fd4;

    --color-secondary: #3a7a9c;
    --color-secondary-hover: #2d6080;

    --color-border: #c2d4e8;
    --color-card-bg: #f8fbff;
    --color-accent-bg: #deeaf6;

    --shadow-sm: 0 1px 3px rgba(20, 40, 80, 0.08);
    --shadow-md: 0 2px 8px rgba(20, 40, 80, 0.12);

    --radius: 3px;
    --radius-lg: 6px;

    --max-width: 1100px;
    --font-serif: 'Georgia', 'Times New Roman', serif;
    --font-sans: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    --font-mono: 'SF Mono', Monaco, 'Cascadia Code', Consolas, monospace;
}

/* ==================== RESET & BASE ==================== */
*, *::before, *::after {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

html { scroll-behavior: smooth; }

body {
    font-family: var(--font-sans);
    background-color: var(--color-bg);
    color: var(--color-text);
    line-height: 1.6;
    font-size: 15px;
    -webkit-font-smoothing: antialiased;
}

a {
    color: var(--color-primary);
    text-decoration: none;
    transition: color 0.2s;
}

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

img { max-width: 100%; height: auto; display: block; }

section { padding: 48px 0; }
section:nth-child(even) { background-color: var(--color-bg-alt); }

/* ==================== LAYOUT ==================== */
.container {
    max-width: var(--max-width);
    margin: 0 auto;
    padding: 0 28px;
}

/* ==================== HEADER ==================== */
.site-header {
    background: linear-gradient(180deg, #ffffff 0%, var(--color-bg) 100%);
    padding: 64px 0 48px;
    text-align: center;
    border-bottom: 1px solid var(--color-border);
}

.paper-title {
    font-family: var(--font-serif);
    font-size: clamp(1.8rem, 4vw, 2.8rem);
    font-weight: 700;
    color: var(--color-text);
    line-height: 1.25;
    margin-bottom: 28px;
    letter-spacing: -0.01em;
}

.authors {
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    gap: 6px 18px;
    margin-bottom: 12px;
}

.author { font-size: 1rem; }

.author a {
    color: var(--color-text);
    font-weight: 500;
}

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

.author sup {
    color: var(--color-text-muted);
    font-size: 0.68em;
    margin-left: 2px;
}

.affiliations {
    color: var(--color-text-light);
    font-size: 0.88rem;
    margin-bottom: 32px;
    line-height: 1.6;
}

.affiliations sup {
    color: var(--color-text-muted);
    font-size: 0.7em;
}

/* ==================== BUTTON BAR ==================== */
.button-bar {
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    gap: 10px;
}

.btn {
    display: inline-flex;
    align-items: center;
    gap: 7px;
    padding: 9px 20px;
    border-radius: var(--radius);
    font-size: 0.92rem;
    font-weight: 500;
    transition: all 0.15s ease;
    border: 1px solid var(--color-border);
    cursor: pointer;
    background: transparent;
    color: var(--color-text);
    text-decoration: none;
}

.btn:hover { text-decoration: none; }

.btn-primary {
    background-color: var(--color-primary);
    border-color: var(--color-primary);
    color: #fff;
}

.btn-primary:hover {
    background-color: var(--color-primary-hover);
    border-color: var(--color-primary-hover);
    color: #fff;
}

.btn-secondary:hover {
    background-color: var(--color-accent-bg);
    border-color: var(--color-text-muted);
}

.btn .icon {
    width: 16px;
    height: 16px;
    flex-shrink: 0;
}

/* ==================== SECTION HEADINGS ==================== */
.abstract-section h2,
.comparison-section h2,
.control-section h2,
.citation-section h2,
.acknowledgements-section h2 {
    font-family: var(--font-serif);
    font-size: 1.65rem;
    font-weight: 700;
    margin-bottom: 20px;
    color: var(--color-text);
    border-bottom: 2px solid var(--color-border);
    padding-bottom: 10px;
}

.section-desc {
    color: var(--color-text-light);
    font-size: 0.95rem;
    margin-bottom: 14px;
    line-height: 1.6;
}

.section-highlights {
    list-style: none;
    padding: 0;
    margin: 0 0 28px 0;
    display: flex;
    flex-direction: column;
    gap: 10px;
}

.section-highlights li {
    padding: 12px 16px 12px 46px;
    border: 1px solid var(--color-border);
    border-radius: var(--radius-lg);
    background: var(--color-card-bg);
    font-size: 0.94rem;
    color: var(--color-text);
    line-height: 1.6;
    position: relative;
}

.section-highlights li:first-child::before {
    content: "①";
    position: absolute;
    left: 14px;
    top: 12px;
    font-size: 1.05rem;
    color: var(--color-primary);
    font-weight: 700;
}

.section-highlights li:last-child::before {
    content: "②";
    position: absolute;
    left: 14px;
    top: 12px;
    font-size: 1.05rem;
    color: #5a7a6a;
    font-weight: 700;
}

/* Single-item robot highlight (used in comparisons section) */
.section-highlights li.highlight-robot {
    padding-left: 52px;
    border-color: #b8d4c8;
    background: #f2f8f5;
}

.section-highlights li.highlight-robot::before {
    content: "🤖";
    font-size: 1.1rem;
    color: unset;
    top: 11px;
}

/* Override :last-child rule when it is also the only child */
.section-highlights li.highlight-robot:last-child::before {
    content: "🤖";
    color: unset;
}

/* ==================== ABSTRACT ==================== */
.abstract-section p {
    font-size: 0.97rem;
    margin-bottom: 12px;
    color: var(--color-text);
    text-align: justify;
}

/* ==================== TEASER FIGURE ==================== */
.teaser-figure {
    margin: 36px 0 0;
    text-align: center;
}

.teaser-img {
    width: 100%;
    height: auto;
    display: block;
    border-radius: var(--radius-lg);
}

.teaser-figure figcaption {
    margin-top: 14px;
    color: var(--color-text-light);
    font-size: 0.9rem;
    line-height: 1.55;
    text-align: left;
}

/* ==================== COMPARISON SECTION ==================== */
.comparison-section { background-color: var(--color-bg-alt); }

.comparison-group {
    margin-bottom: 28px;
    border: 1px solid var(--color-border);
    border-radius: var(--radius-lg);
    overflow: hidden;
    box-shadow: var(--shadow-sm);
}

.comparison-label-row {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 1px;
    background: var(--color-border);
}

.method-label {
    text-align: center;
    font-size: 0.8rem;
    font-weight: 700;
    padding: 9px 4px;
    letter-spacing: 0.04em;
    text-transform: uppercase;
}

.label-wanmove { background: #dce8f8; color: #1a4080; }  /* steel blue  */
.label-wanfun  { background: #fde8d0; color: #8a3a00; }  /* warm amber  */
.label-ours    { background: #d0f0e4; color: #0f5c38; }  /* teal green  */
.label-gt      { background: #e8d8f8; color: #52108a; }  /* soft violet */

.comparison-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 1px;
    background: var(--color-border);
}

.comparison-item {
    background: #000;
    overflow: hidden;
    position: relative;
}

.comparison-item video {
    width: 100%;
    display: block;
    object-fit: cover;
    aspect-ratio: 16 / 9;
}

/* ==================== CONTROL SECTION ==================== */
.control-section { background-color: var(--color-bg); }

.control-cases-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 24px;
}

.control-case {
    border: 1px solid var(--color-border);
    border-radius: var(--radius-lg);
    overflow: hidden;
    box-shadow: var(--shadow-sm);
    background: var(--color-card-bg);
}

.control-case-header {
    display: flex;
    align-items: center;
    gap: 10px;
    padding: 12px 16px;
    background: var(--color-accent-bg);
    border-bottom: 1px solid var(--color-border);
}

.control-id {
    background: var(--color-primary);
    color: white;
    font-size: 0.72rem;
    font-weight: 700;
    padding: 3px 10px;
    border-radius: 20px;
    letter-spacing: 0.03em;
    text-transform: uppercase;
    white-space: nowrap;
    flex-shrink: 0;
}

.control-case-title {
    font-size: 0.92rem;
    font-weight: 600;
    color: var(--color-text);
    line-height: 1.35;
}

.control-pair {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 1px;
    background: var(--color-border);
}

.control-item { background: #000; overflow: hidden; }

.control-item-label {
    text-align: center;
    font-size: 0.78rem;
    font-weight: 600;
    padding: 6px;
    background: #f8f8f8;
    color: var(--color-text-light);
    letter-spacing: 0.04em;
    text-transform: uppercase;
    border-bottom: 1px solid var(--color-border);
}

.control-item video {
    width: 100%;
    display: block;
    aspect-ratio: 16 / 9;
    object-fit: cover;
}


/* ==================== CITATION ==================== */
.citation-section { background-color: var(--color-bg-alt); }

.citation-section p {
    font-size: 0.95rem;
    color: var(--color-text-light);
    margin-bottom: 16px;
}

.bibtex-box {
    position: relative;
    background: var(--color-card-bg);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-lg);
    overflow: hidden;
}

.bibtex-box pre {
    padding: 20px 24px;
    overflow-x: auto;
    font-family: var(--font-mono);
    font-size: 0.83rem;
    line-height: 1.6;
    color: var(--color-text);
    white-space: pre;
}

.copy-btn {
    position: absolute;
    top: 12px;
    right: 12px;
    background: var(--color-accent-bg);
    border: 1px solid var(--color-border);
    color: var(--color-text-light);
    font-size: 0.8rem;
    font-weight: 500;
    padding: 5px 12px;
    border-radius: var(--radius);
    cursor: pointer;
    transition: all 0.15s;
    font-family: var(--font-sans);
}

.copy-btn:hover {
    background: var(--color-border);
    color: var(--color-text);
}

/* ==================== ACKNOWLEDGEMENTS ==================== */
.acknowledgements-section p {
    font-size: 0.93rem;
    color: var(--color-text-light);
    margin-bottom: 8px;
    line-height: 1.6;
}

/* ==================== FOOTER ==================== */
.site-footer {
    text-align: center;
    padding: 24px;
    font-size: 0.82rem;
    color: var(--color-text-muted);
    border-top: 1px solid var(--color-border);
    background: var(--color-bg);
}

.site-footer a { color: var(--color-text-muted); }
.site-footer a:hover { color: var(--color-primary); }

/* ==================== RESPONSIVE ==================== */
@media (max-width: 900px) {
    .comparison-label-row,
    .comparison-grid {
        grid-template-columns: repeat(2, 1fr);
    }

    .control-cases-grid {
        grid-template-columns: 1fr;
    }
}

@media (max-width: 600px) {
    .paper-title { font-size: 1.6rem; }

    .comparison-label-row,
    .comparison-grid {
        grid-template-columns: repeat(2, 1fr);
    }

    .control-pair {
        grid-template-columns: 1fr;
    }

    /* aspect-ratio already handles responsive sizing; no override needed */

    .btn { padding: 8px 14px; font-size: 0.85rem; }
}