.about-header { text-align: center; margin-bottom: 40px; }
.about-header h1 { font-size: 2.2em; font-weight: 900; margin-bottom: 10px; color: var(--text-strong); }

.about-tabs { display: flex; justify-content: center; gap: 15px; margin-bottom: 40px; }
.a-tab { padding: 12px 30px; border-radius: 30px; font-weight: 900; font-size: 1.1em; cursor: pointer; border: 2px solid var(--border-main); background: var(--bg-container); color: var(--text-muted); transition: all 0.3s; }
.a-tab:hover { border-color: var(--text-light); color: var(--text-strong); transform: translateY(-2px); }
.a-tab.active { background: var(--c-indigo); color: white; border-color: var(--c-indigo); box-shadow: 0 5px 15px rgba(79, 70, 229, 0.3); transform: none; }

.a-content { display: none; animation: fadeIn 0.5s ease; }
.a-content.active { display: block; }

.timeline-wrap { max-width: 700px; margin: 0 auto; padding: 20px; }
.timeline-track { 
    position: relative; 
    padding-left: 30px; 
}

.timeline-track::before {
    content: '';
    position: absolute;
    left: -9px;
    top: 0;
    bottom: 0;
    width: 20px;
    background-color: var(--border-main);
    -webkit-mask-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='20' height='40' viewBox='0 0 20 40'%3E%3Cline x1='10' y1='0' x2='10' y2='40' stroke='black' stroke-width='2'/%3E%3Cpolyline points='5,18 10,10 15,18' fill='none' stroke='black' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'/%3E%3C/svg%3E");
    mask-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='20' height='40' viewBox='0 0 20 40'%3E%3Cline x1='10' y1='0' x2='10' y2='40' stroke='black' stroke-width='2'/%3E%3Cpolyline points='5,18 10,10 15,18' fill='none' stroke='black' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'/%3E%3C/svg%3E");
    -webkit-mask-repeat: repeat-y;
    mask-repeat: repeat-y;
    -webkit-mask-position: center 0;
    mask-position: center 0;
    z-index: 0;
    animation: arrowFlowUp 2s linear infinite;
}

@keyframes arrowFlowUp {
    from { 
        -webkit-mask-position: center 0; 
        mask-position: center 0; 
    }
    to { 
        -webkit-mask-position: center -40px; 
        mask-position: center -40px; 
    }
}
.timeline-item { position: relative; margin-bottom: 40px; }
.timeline-item:last-child { margin-bottom: 0; }
.timeline-marker { position: absolute; left: -39px; top: 0; width: 16px; height: 16px; border-radius: 50%; background: var(--c-indigo); border: 4px solid var(--bg-container); box-shadow: 0 0 0 2px rgba(79, 70, 229, 0.2); }
.timeline-date { font-weight: 900; color: var(--c-indigo); font-size: 0.95em; margin-bottom: 8px; letter-spacing: 1px; }
.timeline-title { font-size: 1.2em; font-weight: 900; color: var(--text-strong); margin-bottom: 12px; }
.timeline-body { background: var(--bg-section); padding: 20px; border-radius: 16px; border: 1px solid var(--border-main); color: var(--text-main); font-size: 0.95em; line-height: 1.6; }
.timeline-body ul { margin: 0; padding-left: 20px; }
.timeline-body li { margin-bottom: 6px; }
.timeline-body li:last-child { margin-bottom: 0; }
.tl-group { margin-top: 16px; }
.tl-group:first-child { margin-top: 0; }
.tl-group-label { font-weight: 900; font-size: 0.85em; color: var(--text-muted); letter-spacing: 0.5px; margin: 0 0 8px; padding-bottom: 6px; border-bottom: 1px dashed var(--border-main); }

.intro-section { margin-bottom: 40px; }
.intro-title { font-size: 1.5em; font-weight: 900; color: var(--text-strong); margin-bottom: 20px; }

.intro-card {
    background: var(--bg-container); padding: 30px; border-radius: 20px;
    border: 1px solid var(--border-main); box-shadow: 0 4px 15px rgba(0,0,0,0.02);
    line-height: 1.6; color: var(--text-main); font-size: 1.05em;
}
.intro-card p { margin-top: 0; }
.intro-p-mb { margin-bottom: 25px; }
.intro-p-last { margin-bottom: 0; }

.intro-list { list-style: none; padding: 0; margin: 0 0 25px 0; }
.intro-li { display: flex; gap: 15px; margin-bottom: 20px; }
.intro-li:last-child { margin-bottom: 0; }

.intro-icon {
    color: white; width: 32px; height: 32px; display: flex; align-items: center;
    justify-content: center; border-radius: 50%; font-weight: 900; flex-shrink: 0;
}
.intro-icon.blue { background: var(--c-blue); }
.intro-icon.purple { background: var(--c-purple); }
.intro-icon.red { background: var(--c-red); }
.intro-icon.green { background: var(--c-green); }

.intro-item-title { margin: 0 0 8px 0; color: var(--text-strong); font-size: 1.1em; }
.intro-item-desc { margin: 0; color: var(--text-muted); font-size: 0.95em; }

.about-container { max-width: 850px; margin-top: 40px; }

.about-stats-wrap {
    display: block;
    margin-top: 0;
    padding: 0;
    border: none;
    box-shadow: none;
    background: transparent;
}
.about-stats-wrap .stat-box,
.about-stats-wrap .stat-sub,
.about-stats-wrap .stat-card { border-radius: 20px; }

.stat-hero-dark {
    background: linear-gradient(135deg, #1e293b 0%, #0f172a 100%);
    text-align: center;
    border-radius: 20px;
}
.stat-hero-title {
    color: #fff;
    font-size: 1.8em;
    margin: 0 0 10px 0;
    font-weight: 900;
    letter-spacing: -0.5px;
}
.stat-hero-desc { color: #cbd5e1; font-size: 1.1em; margin: 0; }
.stat-hero-count { color: #38bdf8; font-size: 1.3em; }

.about-deep-stats { margin-top: 40px; }
.stats-section-title {
    text-align: center;
    color: var(--text-strong);
    margin-bottom: 20px;
    font-size: 1.3em;
    font-weight: 900;
}
.about-ranking-section { margin-top: 50px; }
.ranking-board {
    background: var(--bg-card);
    padding: 20px;
    border-radius: 20px;
    border: 1px solid var(--border-main);
}

.marker-indigo { background: var(--c-indigo); }
.marker-teal   { background: var(--c-teal); }
.marker-orange { background: var(--c-orange); }
.marker-purple { background: var(--c-purple); }
.marker-blue   { background: var(--c-blue); }
.marker-green  { background: var(--c-green); }
.marker-muted  { background: var(--text-muted); }

.date-indigo { color: var(--c-indigo); }
.date-teal   { color: var(--c-teal); }
.date-orange { color: var(--c-orange); }
.date-purple { color: var(--c-purple); }
.date-blue   { color: var(--c-blue); }
.date-green  { color: var(--c-green); }
.date-muted  { color: var(--text-muted); }

.footer-copyright-mt { margin-top: 25px; }