/* ============================================================
   LAYOUT STRUCTURES
   ============================================================ */

#header {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    z-index: 1000;
    padding: 0 40px;
    height: 68px;
    display: flex;
    align-items: center;
    justify-content: space-between;
    background: var(--header-bg);
    backdrop-filter: blur(12px) saturate(180%);
    -webkit-backdrop-filter: blur(12px) saturate(180%);
    border-bottom: 1px solid var(--header-border);
    transition: all 0.35s ease;
}

#header.scrolled {
    background: var(--surface-elev);
    border-bottom-color: var(--accent-border-soft);
    box-shadow: 0 12px 28px color-mix(in srgb, var(--bg) 68%, transparent);
}

.logo {
    font-family: var(--font-display);
    font-size: 1.2rem;
    font-weight: 700;
    letter-spacing: -.02em;
    background: var(--grad);
    -webkit-background-clip: text;
    background-clip: text;
    -webkit-text-fill-color: transparent;
}

.nav-links {
    display: flex;
    align-items: center;
    gap: 8px;
}

.nav-links a {
    font-size: .88rem;
    font-weight: 600;
    letter-spacing: 0.01em;
    padding: 8px 14px;
    border-radius: 999px;
    color: var(--text-muted);
    transition: var(--transition);
    border: 1px solid transparent;
    position: relative;
}

/* T2-E: Sliding underline on nav links */
.nav-links a::after {
    content: '';
    position: absolute;
    bottom: 4px;
    left: 14px;
    right: 14px;
    height: 2px;
    background: var(--accent);
    border-radius: 2px;
    transform: scaleX(0);
    transform-origin: left;
    transition: transform 0.2s ease;
}

.nav-links a:hover::after,
.nav-links a.active::after {
    transform: scaleX(1);
}

.nav-links.active {
    display: flex !important;
    position: fixed;
    top: 68px;
    left: 0;
    right: 0;
    bottom: 0;
    background: var(--bg);
    flex-direction: column;
    padding: 40px;
    gap: 20px;
    z-index: 1001;
    animation: fadeIn 0.3s ease;
}

.nav-links.active a {
    font-size: 1.5rem;
    width: 100%;
    text-align: center;
}

.header-actions {
    display: flex;
    align-items: center;
    gap: 12px;
}

.mobile-menu-toggle {
    display: none;
    flex-direction: column;
    gap: 5px;
    background: none;
    border: none;
    cursor: pointer;
    padding: 5px;
}

.mobile-menu-toggle .bar {
    width: 25px;
    height: 2px;
    background: var(--text);
    border-radius: 2px;
    transition: 0.3s ease;
}

.mobile-menu-toggle.active .bar:nth-child(1) {
    transform: translateY(7px) rotate(45deg);
}

.mobile-menu-toggle.active .bar:nth-child(2) {
    opacity: 0;
}

.mobile-menu-toggle.active .bar:nth-child(3) {
    transform: translateY(-7px) rotate(-45deg);
}

#main {
    padding-top: 100px;
    padding-bottom: 120px;
}

.tab-pane>.section:first-of-type {
    padding-top: clamp(6.2rem, 9vw, 7.5rem);
}

/* --- TAB SWITCHER LOGIC --- */
.tab-switcher {
    display: flex;
    justify-content: center;
    gap: 15px;
    margin-bottom: 30px;
}

.tab-switcher.bottom-dock {
    position: fixed;
    bottom: 30px;
    left: 50%;
    transform: translateX(-50%);
    background: var(--surface-elev);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    padding: 10px 15px;
    border-radius: 40px;
    border: 1px solid var(--card-border);
    box-shadow: 0 14px 36px color-mix(in srgb, var(--bg) 72%, transparent);
    z-index: 1000;
    margin-bottom: 0;
    overflow: hidden;
}

.tab-switcher-indicator {
    position: absolute;
    top: 10px;
    height: calc(100% - 20px);
    background: var(--grad);
    border-radius: 30px;
    box-shadow: 0 8px 20px color-mix(in srgb, var(--glow) 52%, transparent);
    transition: left 0.3s cubic-bezier(0.4, 0, 0.2, 1), width 0.3s cubic-bezier(0.4, 0, 0.2, 1);
    pointer-events: none;
    z-index: 0;
}

.tab-btn {
    padding: 10px 24px;
    border-radius: 30px;
    background: transparent;
    border: 1px solid transparent;
    color: var(--text-muted);
    font-size: 0.95rem;
    font-weight: 600;
    cursor: pointer;
    transition: color var(--motion-fast) ease;
    position: relative;
    z-index: 1;
}

.tab-btn:hover {
    color: var(--text);
    border-color: transparent;
    transform: none;
}

.tab-btn.active {
    background: transparent;
    color: #fff;
    border-color: transparent;
    box-shadow: none;
}

.tab-pane {
    display: none;
    opacity: 0;
    transition: opacity 0.4s ease;
}

.tab-pane.active {
    display: block;
    opacity: 1;
}

.section-inner {
    width: min(1160px, 100%);
    margin: 0 auto;
    padding: 0 20px;
    display: grid;
    gap: var(--space-content);
}

.highlights-grid,
.expertise-grid,
.projects-grid {
    display: grid;
    gap: 24px;
}

.highlights-grid {
    grid-template-columns: repeat(4, minmax(0, 1fr));
}

.expertise-grid {
    grid-template-columns: repeat(3, minmax(0, 1fr));
}

.projects-grid {
    grid-template-columns: repeat(2, minmax(0, 1fr));
}

#prof-pane .section {
    padding-block: clamp(4.5rem, 8vw, 6rem);
}

#prof-pane .section:first-child {
    padding-top: clamp(6.2rem, 9vw, 7.6rem);
}

#prof-pane .section-label {
    margin-bottom: 8px;
}

#prof-pane .section-title {
    margin-bottom: 22px;
}

#hero-prof .hero-inner {
    align-items: center;
    gap: 52px;
}

#hero-prof .hero-visual {
    flex: 0.9;
}

#hero-prof .hero-content {
    flex: 1.1;
    max-width: 630px;
}

#hero-prof .hero-image-container {
    max-width: 360px;
}

#hero-prof .hero-ctas {
    margin-top: 20px;
}

/* --- SECTION STRUCTURE --- */
.section {
    padding: var(--section-gap) 0;
    position: relative;
}

.section.bg2 {
    background: linear-gradient(180deg,
            color-mix(in srgb, var(--bg2) 88%, transparent),
            color-mix(in srgb, var(--bg) 94%, transparent));
}

/* --- HERO SECTIONS --- */
.hero {
    display: flex;
    align-items: center;
    padding: clamp(6.6rem, 9vw, 8.2rem) 0 clamp(4rem, 7vw, 5.2rem);
    position: relative;
    overflow: hidden;
}

.hero::after {
    content: '';
    position: absolute;
    top: -50%;
    left: -50%;
    width: 200%;
    height: 200%;
    background: radial-gradient(circle at 75% 25%, var(--accent) 0%, transparent 40%),
        radial-gradient(circle at 25% 75%, var(--accent2) 0%, transparent 40%);
    z-index: -1;
    filter: blur(80px);
    opacity: 0.15;
    animation: mesh-float 20s infinite alternate ease-in-out;
}

@keyframes mesh-float {
    0% {
        transform: rotate(0deg) scale(1);
    }

    100% {
        transform: rotate(10deg) scale(1.1);
    }
}

.hero-inner {
    max-width: 1100px;
    margin: 0 auto;
    display: flex;
    align-items: center;
    gap: 60px;
    z-index: 1;
}

.hero-visual {
    flex: 1;
    position: relative;
}

.hero-image-container {
    position: relative;
    aspect-ratio: 1;
    max-width: 400px;
    margin: 0 auto;
}

.hero-main-img {
    width: 100%;
    height: auto;
    object-fit: cover;
    border-radius: var(--radius-lg);
}

.hero-content {
    flex: 1.2;
}

.highlights {
    margin-top: -8px;
}

@media (max-width: 900px) {
    .nav-links {
        display: none;
    }

    .mobile-menu-toggle {
        display: flex;
    }

    .hero-inner {
        flex-direction: column;
        text-align: center;
        gap: 40px;
    }

    .highlights-grid {
        grid-template-columns: repeat(2, minmax(0, 1fr));
    }

    .expertise-grid,
    .projects-grid {
        grid-template-columns: 1fr;
    }

    #prof-pane .section {
        padding-block: clamp(3.8rem, 10vw, 4.8rem);
    }

    #hero-prof .hero-content {
        max-width: 100%;
    }
}

/* T1-C: Per-section gradient mesh shifts */
#expertise::before {
    content: '';
    position: absolute;
    inset: 0;
    background: radial-gradient(ellipse 70% 50% at 80% 20%, color-mix(in srgb, var(--accent) 7%, transparent), transparent 70%);
    pointer-events: none;
    z-index: 0;
}

#projects::before {
    content: '';
    position: absolute;
    inset: 0;
    background: radial-gradient(ellipse 60% 50% at 10% 80%, color-mix(in srgb, var(--accent2) 8%, transparent), transparent 70%);
    pointer-events: none;
    z-index: 0;
}

#experience::before {
    content: '';
    position: absolute;
    inset: 0;
    background: radial-gradient(ellipse 80% 40% at 90% 50%, color-mix(in srgb, var(--accent) 6%, transparent), transparent 65%);
    pointer-events: none;
    z-index: 0;
}

#research::before {
    content: '';
    position: absolute;
    inset: 0;
    background: radial-gradient(ellipse 55% 60% at 20% 30%, color-mix(in srgb, var(--accent2) 7%, transparent), transparent 70%);
    pointer-events: none;
    z-index: 0;
}

/* T1-D: Orbit chip wrapper */
.orbit-ring {
    position: absolute;
    inset: -28px;
    border-radius: 50%;
    pointer-events: none;
    z-index: 2;
}

.orbit-chip {
    position: absolute;
    top: 50%;
    left: 50%;
    padding: 5px 11px;
    border-radius: 999px;
    background: var(--surface-elev);
    border: 1px solid var(--accent-border-soft);
    color: var(--accent);
    font-size: 0.68rem;
    font-weight: 700;
    font-family: var(--font-mono);
    white-space: nowrap;
    box-shadow: 0 4px 14px color-mix(in srgb, var(--glow) 30%, transparent);
    animation: orbit-chip var(--orbit-dur, 12s) linear infinite;
    animation-delay: var(--orbit-delay, 0s);
    transform-origin: center;
}

@media (prefers-reduced-motion: reduce) {
    .orbit-chip {
        display: none;
    }

    .tab-switcher-indicator {
        transition: none;
    }

    .nav-links a::after {
        transition: none;
    }
}

@media (max-width: 900px) {
    .orbit-ring {
        display: none;
    }
}