.chemistry-hub-page {
    --chemistry-hero-alt: color-mix(in srgb, var(--ph-hero) 80%, var(--ph-chrome-accent));
    --chemistry-hero-text: color-mix(in srgb, var(--ph-surface) 96%, transparent);
    --chemistry-hero-muted: color-mix(in srgb, var(--ph-surface) 68%, transparent);
    --chemistry-hero-line: color-mix(in srgb, var(--ph-surface) 13%, transparent);
    min-height: 100vh;
    margin: 0;
    overflow-x: clip;
    background: var(--ph-bg);
    color: var(--ph-ink);
}

html[data-subject-id="chemistry"] { background: var(--ph-hero); }

.chemistry-skip-link {
    position: fixed;
    top: 8px;
    left: 12px;
    z-index: 2000;
    min-height: 40px;
    display: inline-flex;
    align-items: center;
    padding: 0 14px;
    border: 1px solid var(--ph-line-strong);
    border-radius: var(--ph-radius-control);
    background: var(--ph-surface);
    color: var(--ph-chrome-accent-hover);
    box-shadow: var(--ph-shadow-overlay);
    font-size: calc(13px + var(--ph-type-shift));
    font-weight: 750;
    text-decoration: none;
    transform: translateY(calc(-100% - 20px));
    transition: transform var(--ph-motion-fast) var(--ph-motion-ease);
}

.chemistry-skip-link:focus { transform: translateY(0); }

/* Chemistry is a peer Home surface, so its Header follows the Physics Home
 * presentation grammar instead of the denser application-workspace header. */
.chemistry-top-nav {
    --chemistry-nav-control-height: 36px;
    position: fixed;
    inset: 0 0 auto;
    z-index: 1000;
    padding: 13px 24px;
    transition: width .35s ease, top .35s ease, padding .35s ease, border-color .35s ease, background-color .35s ease, box-shadow .35s ease;
}

.chemistry-nav-container {
    width: min(1200px, 100%);
    min-width: 0;
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 6px;
    margin: 0 auto;
}

.chemistry-nav-logo {
    min-width: 0;
    display: inline-flex;
    align-items: center;
    gap: 10px;
    color: var(--chemistry-hero-text);
    text-decoration: none;
    transition: transform var(--ph-motion-fast) var(--ph-motion-ease);
}

.chemistry-nav-logo:hover,
.chemistry-nav-logo:focus-visible { transform: scale(1.02); }

.chemistry-nav-logo .logo-text {
    color: var(--chemistry-hero-text);
    font-size: calc(20px + var(--ph-type-shift));
    font-weight: 700;
    letter-spacing: -.025em;
}

.chemistry-top-nav .app-nav-mark,
.chemistry-brand-lockup .app-nav-mark {
    position: relative;
    isolation: isolate;
    overflow: hidden;
    filter: none !important;
    transition: box-shadow var(--ph-motion-panel) var(--ph-motion-ease), transform var(--ph-motion-panel) var(--ph-motion-ease);
}

.chemistry-top-nav .app-nav-mark::after,
.chemistry-brand-lockup .app-nav-mark::after {
    content: "";
    position: absolute;
    inset: 0;
    z-index: 1;
    border-radius: inherit;
    pointer-events: none;
    background: linear-gradient(145deg, var(--ph-chrome-accent-hover), var(--ph-hero-accent));
    mix-blend-mode: color;
    opacity: .88;
}

.chemistry-top-nav .app-nav-mark {
    width: 23px;
    height: 23px;
    border-radius: 8px;
    box-shadow:
        0 0 0 1px color-mix(in srgb, var(--ph-hero-accent) 30%, transparent),
        0 7px 18px color-mix(in srgb, var(--ph-chrome-accent) 24%, transparent);
}

.chemistry-top-nav > .nav-container > .physics-language-switch,
.chemistry-top-nav > .nav-container > .physics-text-size-switch .physics-text-size-trigger,
.chemistry-top-nav .nav-auth .nav-admin-quick,
.chemistry-top-nav .nav-auth .app-account-chip {
    height: var(--chemistry-nav-control-height);
    min-height: var(--chemistry-nav-control-height);
}

.chemistry-top-nav > .nav-container > .physics-language-switch,
.chemistry-top-nav > .nav-container > .physics-text-size-switch .physics-text-size-trigger,
.chemistry-top-nav .nav-auth .nav-admin-quick {
    border-radius: 11px;
}

.chemistry-top-nav > .nav-container > .physics-language-switch,
.chemistry-top-nav > .nav-container > .physics-text-size-switch .physics-text-size-trigger {
    border-color: var(--chemistry-hero-line);
    background: color-mix(in srgb, var(--ph-surface) 7%, transparent);
    color: var(--chemistry-hero-muted);
    box-shadow: inset 0 1px color-mix(in srgb, var(--ph-surface) 5%, transparent);
}

.chemistry-top-nav .physics-language-switch button { color: var(--chemistry-hero-muted); }
.chemistry-top-nav .physics-language-switch button.is-active {
    background: color-mix(in srgb, var(--ph-surface) 13%, transparent);
    color: var(--chemistry-hero-text);
}

.chemistry-top-nav .physics-text-size-trigger strong { color: var(--chemistry-hero-text); }
.chemistry-top-nav > .nav-container > .physics-text-size-switch { margin-right: 6px; }

.chemistry-top-nav .nav-auth {
    min-width: 0;
    display: flex;
    align-items: center;
    justify-content: flex-end;
    gap: 6px;
}

.chemistry-top-nav .nav-auth .nav-admin-quick {
    width: 110px;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: 0 9px;
    border: 1px solid var(--chemistry-hero-line);
    background: color-mix(in srgb, var(--ph-surface) 5%, transparent);
    color: color-mix(in srgb, var(--ph-surface) 82%, transparent);
    font-size: calc(10px + var(--ph-type-shift));
    font-weight: 690;
    text-decoration: none;
    white-space: nowrap;
    transition: background-color var(--ph-motion-fast) ease, border-color var(--ph-motion-fast) ease, color var(--ph-motion-fast) ease;
}

.chemistry-top-nav .nav-auth .nav-admin-quick:hover,
.chemistry-top-nav .nav-auth .nav-admin-quick:focus-visible {
    border-color: color-mix(in srgb, var(--ph-surface) 24%, transparent);
    background: color-mix(in srgb, var(--ph-surface) 10%, transparent);
    color: var(--chemistry-hero-text);
}

.chemistry-top-nav .nav-auth .nav-admin-label-compact { display: none; }

.chemistry-top-nav .nav-auth .app-account-chip {
    display: grid;
    grid-template-columns: 26px minmax(0, auto);
    align-items: center;
    gap: 7px;
    padding: 4px 9px 4px 4px;
    border: 1px solid color-mix(in srgb, var(--ph-surface) 18%, transparent);
    border-radius: 12px;
    background: color-mix(in srgb, var(--ph-surface) 9%, transparent);
    color: var(--chemistry-hero-text);
    text-decoration: none;
    box-shadow: inset 0 1px color-mix(in srgb, var(--ph-surface) 8%, transparent);
    transition: background-color var(--ph-motion-fast) ease, border-color var(--ph-motion-fast) ease, transform var(--ph-motion-fast) var(--ph-motion-ease);
}

.chemistry-top-nav .nav-auth .app-account-chip:hover,
.chemistry-top-nav .nav-auth .app-account-chip:focus-visible {
    border-color: color-mix(in srgb, var(--ph-surface) 25%, transparent);
    background: color-mix(in srgb, var(--ph-surface) 13%, transparent);
    transform: translateY(-1px);
}

.chemistry-top-nav .nav-auth .app-account-avatar { width: 26px; height: 26px; border-radius: 9px; font-size: 10px; }
.chemistry-top-nav .nav-auth .app-account-avatar-wrap { width: 26px; height: 26px; }
.chemistry-top-nav .nav-auth .app-account-copy { min-width: 0; display: grid; align-content: center; gap: 1px; line-height: 1.08; }
.chemistry-top-nav .nav-auth .app-account-copy strong {
    max-width: 120px;
    overflow: hidden;
    color: inherit;
    font-size: calc(11.5px + var(--ph-type-shift));
    font-weight: 690;
    text-overflow: ellipsis;
    white-space: nowrap;
}
.chemistry-top-nav .nav-auth .app-account-copy small {
    margin-top: 2px;
    color: var(--chemistry-hero-muted);
    font-size: calc(8px + var(--ph-type-shift));
    font-weight: 650;
    letter-spacing: .07em;
    text-transform: uppercase;
    white-space: nowrap;
}

/* Account roles keep one semantic palette across both Hubs, while the chip
 * surface is mixed with Chemistry's own Hero/Chrome tokens. This preserves
 * role recognition without importing Physics-specific green backgrounds. */
.chemistry-top-nav:not(.scrolled) .nav-auth .app-account-chip:is(.account-type-vip-student, .account-type-teacher, .account-type-admin, .account-type-super-admin) {
    border-color: color-mix(in srgb, var(--account-identity-ring) 82%, var(--chemistry-hero-line));
    background: linear-gradient(135deg,
        color-mix(in srgb, var(--ph-hero) 84%, var(--account-identity-badge)),
        color-mix(in srgb, var(--chemistry-hero-alt) 86%, var(--account-identity-badge)));
    box-shadow: inset 0 1px color-mix(in srgb, var(--ph-surface) 10%, transparent), 0 7px 20px color-mix(in srgb, var(--account-identity-glow) 76%, transparent);
}

.chemistry-top-nav:not(.scrolled) .nav-auth .app-account-chip:is(.account-type-vip-student, .account-type-teacher, .account-type-admin, .account-type-super-admin) .app-account-copy strong {
    color: var(--account-identity-name-on-hero);
}

.chemistry-top-nav:not(.scrolled) .nav-auth .app-account-chip:is(.account-type-vip-student, .account-type-teacher, .account-type-admin, .account-type-super-admin) .account-role-label {
    color: var(--account-identity-label-on-hero);
}

.chemistry-top-nav.scrolled .nav-auth .app-account-chip:is(.account-type-vip-student, .account-type-teacher, .account-type-admin, .account-type-super-admin) {
    border-color: color-mix(in srgb, var(--account-identity-ring) 72%, var(--ph-line));
    background: var(--account-identity-chip);
    box-shadow: inset 0 1px color-mix(in srgb, var(--ph-surface) 84%, transparent), 0 5px 14px var(--account-identity-glow);
}

.chemistry-top-nav.scrolled .nav-auth .app-account-chip:is(.account-type-vip-student, .account-type-teacher, .account-type-admin, .account-type-super-admin) .app-account-copy strong {
    color: var(--account-identity-name-on-surface);
}

.chemistry-top-nav.scrolled .nav-auth .app-account-chip:is(.account-type-vip-student, .account-type-teacher, .account-type-admin, .account-type-super-admin) .account-role-label {
    color: var(--account-identity-label-on-surface);
}

.chemistry-top-nav .nav-auth .login-link {
    min-height: var(--chemistry-nav-control-height);
    display: inline-flex;
    align-items: center;
    padding: 0 18px;
    border: 1px solid var(--chemistry-hero-line);
    border-radius: 11px;
    background: color-mix(in srgb, var(--ph-surface) 8%, transparent);
    color: var(--chemistry-hero-text);
    font-size: calc(13px + var(--ph-type-shift));
    font-weight: 650;
    text-decoration: none;
}

.chemistry-top-nav.scrolled {
    width: min(1180px, calc(100% - 32px));
    top: 12px;
    right: 0;
    left: 0;
    margin: 0 auto;
    padding: 6px 12px;
    border: 1px solid var(--ph-line);
    border-radius: 18px;
    background: var(--ph-chrome);
    box-shadow: 0 14px 44px color-mix(in srgb, var(--ph-ink) 9%, transparent), inset 0 1px color-mix(in srgb, var(--ph-surface) 80%, transparent);
    -webkit-backdrop-filter: blur(24px) saturate(1.18);
    backdrop-filter: blur(24px) saturate(1.18);
}

.chemistry-top-nav.scrolled .logo-text,
.chemistry-top-nav.scrolled .nav-auth .app-account-chip { color: var(--ph-ink); }
.chemistry-top-nav.scrolled .nav-auth .app-account-copy small { color: var(--ph-ink-tertiary); }
.chemistry-top-nav.scrolled .nav-auth .nav-admin-quick,
.chemistry-top-nav.scrolled > .nav-container > .physics-language-switch,
.chemistry-top-nav.scrolled > .nav-container > .physics-text-size-switch .physics-text-size-trigger {
    border-color: var(--ph-line);
    background: color-mix(in srgb, var(--ph-surface) 58%, transparent);
    color: var(--ph-ink-secondary);
}
.chemistry-top-nav.scrolled .physics-language-switch button { color: var(--ph-ink-secondary); }
.chemistry-top-nav.scrolled .physics-language-switch button.is-active {
    background: var(--ph-chrome-accent);
    color: var(--ph-surface);
}
.chemistry-top-nav.scrolled .physics-text-size-trigger strong { color: var(--ph-ink); }
.chemistry-top-nav.scrolled .nav-auth .login-link {
    border-color: var(--ph-line-strong);
    background: var(--ph-chrome-accent);
    color: var(--ph-surface);
    box-shadow: 0 7px 18px color-mix(in srgb, var(--ph-chrome-accent) 18%, transparent);
}

@media (min-width: 769px) {
    .chemistry-top-nav .nav-auth .app-account-avatar-wrap,
    .chemistry-top-nav .nav-auth .app-account-copy { transform: translateY(-1px); }
}

.chemistry-main { min-width: 0; }
.chemistry-main:focus { outline: 0; }

.chemistry-hero-wrapper {
    position: fixed;
    inset: 0;
    z-index: 1;
    height: 100svh;
    min-height: 650px;
    contain: paint;
}

.chemistry-hero {
    position: relative;
    isolation: isolate;
    width: 100%;
    height: 100%;
    display: flex;
    align-items: center;
    justify-content: center;
    overflow: hidden;
    background:
        radial-gradient(circle at 66% 28%, var(--ph-hero-halo), transparent 32%),
        radial-gradient(circle at 28% 76%, color-mix(in srgb, var(--ph-chrome-accent) 14%, transparent), transparent 37%),
        linear-gradient(150deg, var(--ph-hero), var(--chemistry-hero-alt));
    color: var(--chemistry-hero-text);
}

.chemistry-hero::before {
    content: "";
    position: absolute;
    inset: -12%;
    z-index: 0;
    pointer-events: none;
    background:
        radial-gradient(circle at 48% 24%, color-mix(in srgb, var(--ph-hero-accent) 12%, transparent), transparent 24%),
        radial-gradient(circle at 74% 60%, color-mix(in srgb, var(--ph-chrome-accent) 12%, transparent), transparent 28%);
    animation: chemistry-ambient-breathe 12s ease-in-out infinite alternate;
}

.chemistry-hero::after {
    content: "";
    position: absolute;
    inset: 0;
    z-index: 0;
    pointer-events: none;
    background:
        linear-gradient(180deg, color-mix(in srgb, var(--ph-surface) 2%, transparent), transparent 18%),
        linear-gradient(0deg, color-mix(in srgb, var(--ph-hero) 52%, transparent), transparent 36%);
}

@keyframes chemistry-ambient-breathe {
    from { opacity: .58; transform: scale(1) translate3d(-1%, 0, 0); }
    to { opacity: 1; transform: scale(1.08) translate3d(1%, -1%, 0); }
}

.chemistry-hero-ambient {
    position: absolute;
    width: min(76vw, 980px);
    aspect-ratio: 1;
    top: 44%;
    left: 50%;
    z-index: 1;
    border-radius: 50%;
    pointer-events: none;
    background: conic-gradient(from 120deg, transparent 0 22%, color-mix(in srgb, var(--ph-chrome-accent) 17%, transparent) 35%, transparent 48% 67%, color-mix(in srgb, var(--ph-hero-accent) 14%, transparent) 78%, transparent 92%);
    filter: blur(70px);
    transform: translate(-50%, -50%);
    animation: chemistry-ambient-turn 24s linear infinite;
}

@keyframes chemistry-ambient-turn {
    to { transform: translate(-50%, -50%) rotate(1turn); }
}

.chemistry-hero-inner {
    position: relative;
    z-index: 2;
    width: min(1040px, calc(100% - 64px));
    margin: 0 auto;
    padding: 102px 0 30px;
    text-align: center;
    will-change: transform, opacity;
}

.chemistry-hero-layout {
    position: relative;
    isolation: isolate;
    display: grid;
    place-items: center;
    min-height: clamp(430px, 58vh, 535px);
}

.chemistry-hero-layout::after {
    content: "";
    position: absolute;
    inset: 2% 7% 4%;
    z-index: 2;
    pointer-events: none;
    background: radial-gradient(
        ellipse 57% 67% at 50% 47%,
        color-mix(in srgb, var(--ph-hero) 62%, transparent) 0 28%,
        color-mix(in srgb, var(--ph-hero) 38%, transparent) 48%,
        color-mix(in srgb, var(--ph-hero) 10%, transparent) 66%,
        transparent 78%
    );
}

.chemistry-hero-copy {
    position: relative;
    z-index: 3;
    width: min(100%, 780px);
    min-width: 0;
    margin: 0 auto;
    text-align: center;
}

.chemistry-subject-switcher {
    width: fit-content;
    max-width: 100%;
    display: inline-flex;
    align-items: center;
    gap: 3px;
    margin: 0 auto 24px;
    padding: 3px;
    border: 1px solid var(--chemistry-hero-line);
    border-radius: var(--ph-radius-pill);
    background: color-mix(in srgb, var(--ph-surface) 5%, transparent);
    box-shadow: inset 0 1px color-mix(in srgb, var(--ph-surface) 5%, transparent);
    animation: chemistry-enter-up .85s var(--ph-motion-ease) .16s both;
}

.chemistry-subject-switcher :where(span, a) {
    min-height: 36px;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: 0 12px;
    border: 1px solid transparent;
    border-radius: var(--ph-radius-pill);
    color: var(--chemistry-hero-muted);
    font-size: calc(12.5px + var(--ph-type-shift));
    font-weight: 680;
    line-height: 1;
    text-decoration: none;
    white-space: nowrap;
}

.chemistry-subject-switcher > span {
    gap: 8px;
    padding-inline: 9px;
    font-size: calc(11px + var(--ph-type-shift));
    font-weight: 690;
    letter-spacing: .11em;
    text-transform: uppercase;
}

.chemistry-subject-switcher > span::before {
    content: "";
    width: 5px;
    height: 5px;
    flex: 0 0 5px;
    border-radius: 50%;
    background: var(--ph-hero-accent);
    box-shadow: 0 0 0 4px color-mix(in srgb, var(--ph-hero-accent) 12%, transparent), 0 0 13px color-mix(in srgb, var(--ph-hero-accent) 58%, transparent);
}

.chemistry-subject-switcher a:hover,
.chemistry-subject-switcher a:focus-visible {
    border-color: color-mix(in srgb, var(--ph-surface) 11%, transparent);
    background: color-mix(in srgb, var(--ph-surface) 8%, transparent);
    color: var(--chemistry-hero-text);
}

.chemistry-subject-switcher a.is-current {
    border-color: color-mix(in srgb, var(--ph-hero-accent) 18%, transparent);
    background: color-mix(in srgb, var(--ph-surface) 12%, transparent);
    color: var(--chemistry-hero-text);
    box-shadow: inset 0 1px color-mix(in srgb, var(--ph-surface) 7%, transparent);
}

.chemistry-brand-lockup {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 14px;
    margin: 0 auto 24px;
}

.chemistry-brand-lockup .app-nav-mark {
    width: 50px;
    height: 50px;
    flex: 0 0 auto;
    border-radius: 15px;
    box-shadow:
        0 18px 38px color-mix(in srgb, var(--ph-hero) 48%, transparent),
        0 0 0 1px color-mix(in srgb, var(--ph-hero-accent) 34%, transparent),
        0 0 30px color-mix(in srgb, var(--ph-chrome-accent) 22%, transparent);
    animation: chemistry-enter-up .85s var(--ph-motion-ease) .28s both;
}

.chemistry-brand-lockup h1 {
    width: max-content;
    max-width: 100%;
    margin: -.06em auto -.1em;
    padding: .06em .1em .12em;
    color: var(--chemistry-hero-text);
    font-family: var(--ph-font-display);
    font-size: clamp(60px, 6.7vw, 88px);
    font-weight: 690;
    line-height: 1.08;
    letter-spacing: -.055em;
    animation: chemistry-enter-up .85s var(--ph-motion-ease) .34s both;
}

.chemistry-hero-kicker {
    max-width: 660px;
    margin: 0 auto 28px;
    color: var(--chemistry-hero-text);
    font-size: clamp(22px, 2.4vw, 34px);
    font-weight: 620;
    line-height: 1.14;
    letter-spacing: -.035em;
    animation: chemistry-enter-up .85s var(--ph-motion-ease) .52s both;
}

.chemistry-hero-actions {
    width: fit-content;
    display: inline-flex;
    align-items: center;
    gap: 6px;
    margin: 0 auto;
    padding: 5px;
    border: 1px solid color-mix(in srgb, var(--ph-surface) 10%, transparent);
    border-radius: 19px;
    background: color-mix(in srgb, var(--ph-surface) 4%, transparent);
    box-shadow: inset 0 1px color-mix(in srgb, var(--ph-surface) 5%, transparent), 0 20px 50px color-mix(in srgb, var(--ph-hero) 38%, transparent);
    -webkit-backdrop-filter: blur(16px) saturate(1.08);
    backdrop-filter: blur(16px) saturate(1.08);
    animation: chemistry-enter-up .9s var(--ph-motion-ease) .7s both;
}

.ph-system-page .chemistry-hero-action {
    min-width: 184px;
    min-height: 46px !important;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: 0 21px !important;
    border: 1px solid transparent !important;
    border-radius: 14px !important;
    color: var(--chemistry-hero-text);
    font-size: calc(13px + var(--ph-type-shift));
    font-weight: 680;
    letter-spacing: -.005em;
    text-decoration: none;
    white-space: nowrap;
    transition: transform var(--ph-motion-panel) var(--ph-motion-ease), background-color var(--ph-motion-panel) ease, border-color var(--ph-motion-panel) ease, box-shadow var(--ph-motion-panel) ease;
}

.ph-system-page .chemistry-hero-action.is-primary {
    border-color: color-mix(in srgb, var(--ph-hero-accent) 18%, transparent) !important;
    background: linear-gradient(145deg, var(--ph-chrome-accent-hover), var(--ph-chrome-accent)) !important;
    color: var(--ph-surface) !important;
    box-shadow: 0 11px 28px color-mix(in srgb, var(--ph-chrome-accent) 25%, transparent), inset 0 1px color-mix(in srgb, var(--ph-surface) 17%, transparent);
}

.ph-system-page .chemistry-hero-action.is-secondary {
    border-color: color-mix(in srgb, var(--ph-surface) 9%, transparent) !important;
    background: color-mix(in srgb, var(--ph-surface) 5%, transparent) !important;
    color: color-mix(in srgb, var(--ph-surface) 83%, transparent) !important;
}

.chemistry-hero-action:hover,
.chemistry-hero-action:focus-visible {
    transform: translateY(-2px);
    border-color: color-mix(in srgb, var(--ph-surface) 24%, transparent) !important;
}

.ph-system-page .chemistry-hero-action.is-secondary:hover {
    background: color-mix(in srgb, var(--ph-surface) 9%, transparent) !important;
    color: var(--chemistry-hero-text) !important;
}

.chemistry-scene {
    --chemistry-scene-opacity: .52;
    position: absolute;
    inset: -7% -10%;
    z-index: 1;
    overflow: hidden;
    color: var(--ph-hero-accent);
    opacity: var(--chemistry-scene-opacity);
    pointer-events: none;
    animation: chemistry-scene-enter 1s var(--ph-motion-ease) .44s both;
    -webkit-mask-image: radial-gradient(ellipse 82% 80% at 50% 50%, rgba(0,0,0,.82) 20%, rgba(0,0,0,.64) 62%, transparent 100%);
    mask-image: radial-gradient(ellipse 82% 80% at 50% 50%, rgba(0,0,0,.82) 20%, rgba(0,0,0,.64) 62%, transparent 100%);
}

@keyframes chemistry-scene-enter {
    from { opacity: 0; transform: translateY(18px); }
    to { opacity: var(--chemistry-scene-opacity); transform: translateY(0); }
}

.chemistry-scene::before {
    content: "";
    position: absolute;
    inset: 10% 4% 8% 2%;
    border-radius: 50%;
    background:
        radial-gradient(circle at 24% 64%, color-mix(in srgb, var(--ph-hero-accent) 13%, transparent), transparent 29%),
        radial-gradient(circle at 76% 38%, color-mix(in srgb, var(--ph-chrome-accent) 17%, transparent), color-mix(in srgb, var(--ph-chrome-accent) 5%, transparent) 38%, transparent 70%);
    filter: blur(18px);
}

.chemistry-scene svg {
    width: 100%;
    height: 100%;
    overflow: visible;
    will-change: transform;
}

.chemistry-scene :where(path, circle) { vector-effect: non-scaling-stroke; }
.chemistry-scene-grid { opacity: .42; }
.chemistry-scene-grid path { fill: none; stroke: color-mix(in srgb, var(--ph-surface) 6%, transparent); stroke-width: 1; }
.chemistry-reaction-trails path {
    fill: none;
    stroke-linecap: round;
}
.chemistry-reaction-trail-ghost {
    stroke: color-mix(in srgb, var(--ph-hero-accent) 20%, transparent);
    stroke-width: 1;
    stroke-dasharray: 2 10;
}
.chemistry-reaction-trail-live {
    stroke: var(--ph-hero-accent);
    stroke-width: 1.8;
    stroke-dasharray: 10 126;
    filter: drop-shadow(0 0 6px color-mix(in srgb, var(--ph-hero-accent) 72%, transparent));
    animation: chemistry-reaction-travel 6.8s linear infinite;
}
.chemistry-reaction-trail-live.trail-right { animation-delay: -3.2s; }

@keyframes chemistry-reaction-travel {
    to { stroke-dashoffset: -272; }
}

.chemistry-glow-point {
    fill: var(--ph-hero-accent);
    stroke: color-mix(in srgb, var(--ph-surface) 58%, transparent);
    stroke-width: .8;
    transform-box: fill-box;
    transform-origin: center;
    filter: drop-shadow(0 0 8px color-mix(in srgb, var(--ph-hero-accent) 78%, transparent));
    animation: chemistry-point-breathe 3.6s ease-in-out infinite;
}
.chemistry-glow-point.point-two { animation-delay: -.9s; }
.chemistry-glow-point.point-three { animation-delay: -1.8s; }
.chemistry-glow-point.point-four { animation-delay: -2.7s; }

@keyframes chemistry-point-breathe {
    0%, 100% { opacity: .28; transform: scale(.78); }
    48% { opacity: 1; transform: scale(1.2); }
}
.chemistry-molecule { fill: color-mix(in srgb, currentColor 20%, transparent); stroke: color-mix(in srgb, currentColor 55%, transparent); stroke-width: 1.4; stroke-linecap: round; stroke-linejoin: round; }
.chemistry-molecule circle { fill: color-mix(in srgb, currentColor 74%, var(--ph-hero)); stroke: color-mix(in srgb, var(--ph-surface) 30%, transparent); }
.chemistry-molecule .chemistry-atom-hot { fill: var(--ph-hero-accent); filter: drop-shadow(0 0 11px color-mix(in srgb, var(--ph-hero-accent) 62%, transparent)); }
.chemistry-molecule .chemistry-atom-cool { fill: color-mix(in srgb, var(--ph-chrome-accent) 80%, var(--ph-surface)); }
.chemistry-molecule-main {
    transform-box: fill-box;
    transform-origin: center;
    opacity: .76;
    animation: chemistry-molecule-float 9s ease-in-out infinite alternate;
}

.chemistry-electron-orbit {
    fill: none;
    stroke: color-mix(in srgb, var(--ph-hero-accent) 42%, transparent);
    stroke-width: 1;
    stroke-dasharray: 4 8;
    opacity: .72;
}
.chemistry-electron-orbit .chemistry-electron-satellite {
    transform-box: view-box;
    transform-origin: 705px 306px;
    animation: chemistry-electron-turn 10s linear infinite;
}
.chemistry-electron-orbit .chemistry-electron-satellite circle {
    fill: var(--ph-hero-accent);
    stroke: color-mix(in srgb, var(--ph-surface) 66%, transparent);
    stroke-width: 1;
    filter: drop-shadow(0 0 7px color-mix(in srgb, var(--ph-hero-accent) 82%, transparent));
}

@keyframes chemistry-electron-turn {
    to { transform: rotate(1turn); }
}

@keyframes chemistry-molecule-float {
    from { transform: translate3d(132px, 20px, 0) scale(.82) rotate(-.35deg); }
    to { transform: translate3d(138px, 8px, 0) scale(.82) rotate(.55deg); opacity: .68; }
}

.chemistry-vessel {
    fill: none;
    stroke: color-mix(in srgb, var(--ph-surface) 30%, transparent);
    stroke-width: 1.5;
    stroke-linecap: round;
    stroke-linejoin: round;
    transform-box: fill-box;
    transform-origin: center;
    transform: translate3d(-116px, 34px, 0) scale(.84);
    opacity: .62;
}
.chemistry-vessel .chemistry-liquid { fill: color-mix(in srgb, var(--ph-chrome-accent) 22%, transparent); stroke: color-mix(in srgb, var(--ph-hero-accent) 44%, transparent); }
.chemistry-vessel circle { fill: var(--ph-hero-accent); stroke: none; opacity: .58; }
.chemistry-bubble { animation: chemistry-bubble-rise 4.6s ease-in infinite; transform-origin: center; }
.chemistry-bubble.bubble-two { animation-delay: 1.3s; }
.chemistry-bubble.bubble-three { animation-delay: 2.4s; }

@keyframes chemistry-bubble-rise {
    0% { opacity: 0; transform: translateY(8px) scale(.7); }
    30% { opacity: .62; }
    100% { opacity: 0; transform: translateY(-56px) scale(1.05); }
}

.chemistry-bond-route { display: none; }

.chemistry-hero-stats {
    position: relative;
    z-index: 3;
    width: min(100%, 880px);
    display: grid;
    grid-template-columns: repeat(4, minmax(0, 1fr));
    margin: 10px auto 0;
    padding: 5px;
    border: 1px solid var(--chemistry-hero-line);
    border-radius: 19px;
    background: color-mix(in srgb, var(--ph-surface) 5%, transparent);
    box-shadow: inset 0 1px color-mix(in srgb, var(--ph-surface) 4%, transparent), 0 16px 44px color-mix(in srgb, var(--ph-hero) 32%, transparent);
    -webkit-backdrop-filter: blur(16px);
    backdrop-filter: blur(16px);
    animation: chemistry-enter-up 1s var(--ph-motion-ease) .9s both;
}

.chemistry-hero-stats > div {
    min-width: 0;
    padding: 10px 12px 9px;
    text-align: center;
}

.chemistry-hero-stats > div + div { border-left: 1px solid color-mix(in srgb, var(--ph-surface) 8%, transparent); }
.chemistry-hero-stats strong {
    display: block;
    color: var(--ph-hero-accent);
    font-size: clamp(27px, 3vw, 34px);
    font-weight: 650;
    line-height: 1.1;
    letter-spacing: -.045em;
}
.chemistry-hero-stats span {
    display: block;
    margin-top: 5px;
    color: color-mix(in srgb, var(--ph-surface) 43%, transparent);
    font-size: calc(11px + var(--ph-type-shift));
    font-weight: 650;
    line-height: 1.35;
    letter-spacing: .11em;
    text-transform: uppercase;
}

@keyframes chemistry-enter-up {
    from { opacity: 0; transform: translateY(30px); }
    to { opacity: 1; transform: translateY(0); }
}

.chemistry-hero-fade-overlay {
    position: fixed;
    inset: 0;
    z-index: 5;
    height: 100svh;
    pointer-events: none;
    background: linear-gradient(180deg, transparent 0%, color-mix(in srgb, var(--ph-hero) 2%, transparent) 58%, color-mix(in srgb, var(--ph-bg) 38%, transparent) 100%);
    opacity: 0;
}

.chemistry-course-wrapper {
    position: relative;
    z-index: 10;
    margin-top: 100svh;
    border-radius: 34px 34px 0 0;
    isolation: isolate;
    background:
        radial-gradient(circle at 10% 18%, var(--ph-accent-halo), transparent 38rem),
        radial-gradient(circle at 88% 72%, color-mix(in srgb, var(--ph-chrome-accent) 8%, transparent), transparent 44rem),
        linear-gradient(155deg, color-mix(in srgb, var(--ph-bg) 86%, var(--ph-surface)), var(--ph-bg));
    box-shadow: 0 -1px color-mix(in srgb, var(--ph-surface) 36%, transparent), 0 -24px 80px rgba(0,0,0,.19);
}

.chemistry-section-kicker {
    color: var(--ph-chrome-accent);
    font-size: calc(10px + var(--ph-type-shift));
    font-weight: 820;
    letter-spacing: .1em;
    text-transform: uppercase;
}

.chemistry-course-shell {
    scroll-margin-top: 76px;
    background: transparent;
}

.chemistry-level-tabs {
    position: sticky;
    top: 76px;
    z-index: 80;
    padding: 25px 16px 12px;
    background: transparent;
}

.chemistry-level-tabs-inner {
    width: fit-content;
    max-width: calc(100vw - 32px);
    display: flex;
    justify-content: center;
    gap: 4px;
    margin: 0 auto;
    padding: 5px;
    border: 1px solid var(--ph-line);
    border-radius: 16px;
    background: var(--ph-chrome);
    box-shadow: 0 12px 32px color-mix(in srgb, var(--ph-ink) 8%, transparent), inset 0 1px color-mix(in srgb, var(--ph-surface) 78%, transparent);
    -webkit-backdrop-filter: blur(20px) saturate(1.14);
    backdrop-filter: blur(20px) saturate(1.14);
}

.chemistry-level-tab {
    min-height: 38px;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
    padding: 8px 18px;
    border-radius: 11px;
    color: var(--ph-ink-secondary);
    font-size: calc(13px + var(--ph-type-shift));
    font-weight: 650;
    letter-spacing: -.01em;
    text-decoration: none;
    transition: color var(--ph-motion-panel) ease, background-color var(--ph-motion-panel) ease, box-shadow var(--ph-motion-panel) ease;
}

.chemistry-level-tab::before {
    content: "";
    width: 5px;
    height: 5px;
    flex: 0 0 5px;
    border-radius: 50%;
    background: currentColor;
    opacity: .62;
}

.chemistry-level-tab:hover,
.chemistry-level-tab:focus-visible { background: var(--ph-chrome-accent-soft); color: var(--ph-chrome-accent-hover); }
.chemistry-level-tab.is-active {
    background: linear-gradient(145deg, var(--ph-chrome-accent-hover), var(--ph-chrome-accent));
    color: var(--ph-surface);
    box-shadow: 0 7px 17px color-mix(in srgb, var(--ph-chrome-accent) 19%, transparent), inset 0 1px color-mix(in srgb, var(--ph-surface) 12%, transparent);
}
.chemistry-level-tab.is-active::before {
    background: var(--ph-hero-accent);
    box-shadow: 0 0 0 3px color-mix(in srgb, var(--ph-hero-accent) 13%, transparent);
    opacity: 1;
}

.chemistry-course-intro,
.chemistry-level {
    width: min(1120px, calc(100% - 40px));
    margin-inline: auto;
}

.chemistry-course-intro {
    display: grid;
    grid-template-columns: minmax(0, 1fr) minmax(300px, .72fr);
    align-items: end;
    gap: 40px;
    padding: 58px 0 44px;
}

.chemistry-course-intro h2 {
    max-width: 680px;
    margin: 8px 0 0;
    font-size: clamp(32px, 4.5vw, 52px);
    line-height: 1.07;
    letter-spacing: -.05em;
}
.chemistry-course-intro p { margin: 0; color: var(--ph-ink-secondary); font-size: calc(15px + var(--ph-type-shift)); line-height: 1.72; }

.chemistry-level {
    scroll-margin-top: 138px;
    padding: 28px 0 44px;
}

.chemistry-level + .chemistry-level { border-top: 1px solid var(--ph-line); }

.chemistry-level-heading {
    display: flex;
    align-items: end;
    justify-content: space-between;
    gap: 24px;
    margin-bottom: 22px;
}

.chemistry-level-heading h2 { margin: 6px 0 0; font-size: clamp(27px, 4vw, 42px); letter-spacing: -.045em; }
.chemistry-level-heading > span { color: var(--ph-ink-tertiary); font-size: calc(12px + var(--ph-type-shift)); font-weight: 740; }

.chemistry-domain {
    --chemistry-domain-accent: var(--ph-chrome-accent);
    position: relative;
    overflow: hidden;
    margin-top: 18px;
    padding: 20px;
    border: 1px solid color-mix(in srgb, var(--chemistry-domain-accent) 14%, var(--ph-line));
    border-radius: var(--ph-radius-panel);
    background:
        radial-gradient(circle at 100% 0, color-mix(in srgb, var(--chemistry-domain-accent) 7%, transparent), transparent 18rem),
        color-mix(in srgb, var(--ph-surface) 84%, transparent);
    box-shadow: var(--ph-shadow-card);
}

.chemistry-domain[data-chemistry-domain="inorganic"] {
    --chemistry-domain-accent: color-mix(in srgb, var(--ph-info) 66%, var(--ph-chrome-accent));
}
.chemistry-domain[data-chemistry-domain="organic"] {
    --chemistry-domain-accent: color-mix(in srgb, var(--ph-warning) 64%, var(--ph-chrome-accent));
}
.chemistry-domain[data-chemistry-domain="analysis"] {
    --chemistry-domain-accent: color-mix(in srgb, var(--ph-positive) 62%, var(--ph-chrome-accent));
}
.chemistry-domain[data-chemistry-domain="practical"] {
    --chemistry-domain-accent: color-mix(in srgb, var(--ph-ink-secondary) 76%, var(--ph-chrome-accent));
}

.chemistry-domain-heading {
    display: grid;
    grid-template-columns: 8px minmax(0, 1fr) auto;
    align-items: center;
    gap: 12px;
    padding: 0 2px 14px;
    border-bottom: 1px solid var(--ph-line);
}

.chemistry-domain-mark {
    width: 8px;
    height: 8px;
    border-radius: var(--ph-radius-pill);
    background: var(--chemistry-domain-accent);
    box-shadow: 0 0 0 5px color-mix(in srgb, var(--chemistry-domain-accent) 8%, transparent);
}
.chemistry-domain-heading h3 { margin: 0; color: var(--chemistry-domain-accent); font-size: calc(15px + var(--ph-type-shift)); letter-spacing: -.01em; }
.chemistry-domain-heading > span:last-child {
    min-width: 26px;
    min-height: 26px;
    display: grid;
    place-items: center;
    border-radius: var(--ph-radius-pill);
    background: color-mix(in srgb, var(--chemistry-domain-accent) 7%, var(--ph-surface));
    color: color-mix(in srgb, var(--chemistry-domain-accent) 72%, var(--ph-ink-secondary));
    font-size: calc(10px + var(--ph-type-shift));
    font-weight: 800;
}

.chemistry-topic-grid {
    display: grid;
    grid-template-columns: repeat(3, minmax(0, 1fr));
    gap: 11px;
    margin-top: 14px;
}

.chemistry-topic-card {
    min-width: 0;
    min-height: 148px;
    padding: 17px;
    border: 1px solid color-mix(in srgb, var(--ph-ink-tertiary) 22%, transparent);
    border-radius: var(--ph-radius-card);
    background: linear-gradient(145deg, color-mix(in srgb, var(--ph-ink-tertiary) 5%, var(--ph-surface)), var(--ph-surface-subtle));
    color: var(--ph-ink-secondary);
    box-shadow: var(--ph-shadow-control);
    cursor: not-allowed;
    filter: saturate(.28);
    opacity: .78;
}

.chemistry-topic-card-head {
    display: flex;
    align-items: start;
    justify-content: space-between;
    gap: 9px;
}

.chemistry-topic-number {
    color: var(--ph-ink-tertiary);
    font-size: calc(10px + var(--ph-type-shift));
    font-weight: 820;
    letter-spacing: .07em;
    text-transform: uppercase;
}

.chemistry-topic-status {
    flex: 0 0 auto;
    padding: 4px 7px;
    border: 1px solid color-mix(in srgb, var(--ph-ink-tertiary) 22%, transparent);
    border-radius: var(--ph-radius-pill);
    background: color-mix(in srgb, var(--ph-ink-tertiary) 7%, var(--ph-surface));
    color: var(--ph-ink-tertiary);
    font-size: calc(9px + var(--ph-type-shift));
    font-weight: 760;
    white-space: nowrap;
}

.chemistry-topic-card h4 {
    display: grid;
    gap: 4px;
    margin: 22px 0 0;
    color: var(--ph-ink-secondary);
    font-size: calc(17px + var(--ph-type-shift));
    line-height: 1.28;
    letter-spacing: -.02em;
}

.chemistry-topic-card h4 > span[lang="zh-CN"] {
    display: none;
    color: var(--ph-ink-tertiary);
    font-size: calc(13px + var(--ph-type-shift));
    font-weight: 620;
    letter-spacing: 0;
}

html[lang^="zh"] .chemistry-topic-card h4 > span[lang="zh-CN"] { display: block; }
.chemistry-topic-card p { margin: 11px 0 0; color: var(--ph-ink-tertiary); font-size: calc(12px + var(--ph-type-shift)); line-height: 1.55; }

.chemistry-footer {
    padding: 40px 20px;
    background: var(--ph-hero);
    color: var(--chemistry-hero-muted);
    text-align: center;
}

.chemistry-footer p { margin: 0; font-size: calc(12px + var(--ph-type-shift)); }

.chemistry-footer .site-filing { margin-top: 10px; }

.chemistry-footer .site-filing-link {
    color: inherit;
    text-decoration: none;
    text-underline-offset: 3px;
}

.chemistry-footer .site-filing-link:hover,
.chemistry-footer .site-filing-link:focus-visible {
    color: color-mix(in srgb, var(--chemistry-hero-muted) 58%, var(--ph-surface));
    text-decoration: underline;
}

body.chemistry-hero-resting .chemistry-hero::before,
body.chemistry-hero-resting .chemistry-hero-ambient,
body.chemistry-hero-resting .chemistry-molecule-main,
body.chemistry-hero-resting .chemistry-bubble,
body.chemistry-hero-resting .chemistry-reaction-trail-live,
body.chemistry-hero-resting .chemistry-glow-point,
body.chemistry-hero-resting .chemistry-electron-satellite { animation-play-state: paused; }

@media (max-width: 940px) {
    .chemistry-topic-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); }
    .chemistry-course-intro { grid-template-columns: minmax(0, 1fr); gap: 18px; }
    .chemistry-scene { --chemistry-scene-opacity: .4; inset-inline: -18%; }
}

@media (max-width: 768px) {
    .chemistry-hero-wrapper { min-height: 720px; }
    .chemistry-hero { align-items: flex-start; }
    .chemistry-hero-inner { width: calc(100% - 28px); max-width: 520px; padding: 76px 0 18px; }
    .chemistry-hero-layout { min-height: 500px; }
    .chemistry-hero-layout::after { inset: 2% -4% 1%; }
    .chemistry-scene { --chemistry-scene-opacity: .29; inset: 1% -26px -2%; }
    .chemistry-subject-switcher { width: 100%; margin-bottom: 17px; }
    .chemistry-subject-switcher :where(span, a) { min-width: 0; min-height: 40px; flex: 1 1 auto; padding-inline: 8px; }
    .chemistry-subject-switcher > span { flex: 0 0 auto; gap: 6px; padding-inline: 7px; letter-spacing: .08em; }
    .chemistry-brand-lockup { gap: 12px; margin-bottom: 13px; }
    .chemistry-brand-lockup .app-nav-mark { width: 40px; height: 40px; border-radius: 12px; }
    .chemistry-brand-lockup h1 { font-size: clamp(43px, 12.5vw, 54px); }
    .chemistry-hero-kicker { margin-bottom: 20px; font-size: clamp(20px, 6.1vw, 27px); }
    .chemistry-hero-actions { width: min(100%, 374px); display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 3px; }
    .ph-system-page .chemistry-hero-action { min-width: 0; min-height: 44px !important; padding: 0 9px !important; border-radius: 12px !important; line-height: 1.3; white-space: normal; }
    .chemistry-hero-stats { grid-template-columns: repeat(2, minmax(0, 1fr)); margin-top: 13px; border-radius: 17px; }
    .chemistry-hero-stats > div { padding: 8px 4px; }
    .chemistry-hero-stats > div:nth-child(3) { border-left: 0; }
    .chemistry-hero-stats > div:nth-child(n + 3) { border-top: 1px solid color-mix(in srgb, var(--ph-surface) 8%, transparent); }
    .chemistry-hero-stats strong { font-size: 25px; }
    .chemistry-hero-stats span { font-size: calc(9.5px + var(--ph-type-shift)); line-height: 1.3; letter-spacing: .07em; }
    .chemistry-course-wrapper { margin-top: 100svh; border-radius: 26px 26px 0 0; }
    .chemistry-level-tabs { top: 62px; padding: 18px 10px 8px; }
    .chemistry-level-tabs-inner { max-width: calc(100vw - 20px); padding: 4px; }
    .chemistry-level-tab { min-height: 42px; padding: 8px 12px; }
    .chemistry-course-intro,
    .chemistry-level { width: calc(100% - 20px); }
    .chemistry-course-intro { padding: 48px 0 30px; }
    .chemistry-course-intro h2 { font-size: 34px; }
    .chemistry-level { padding: 24px 0 35px; }
    .chemistry-level-heading { display: grid; gap: 9px; }
    .chemistry-domain { padding: 14px; border-radius: 17px; }
    .chemistry-topic-grid { grid-template-columns: minmax(0, 1fr); gap: 8px; }
    .chemistry-topic-card { min-height: 130px; padding: 15px; }
    .chemistry-topic-card h4 { margin-top: 18px; }

    .chemistry-top-nav { padding: 8px 14px; }
    .chemistry-top-nav.scrolled { width: calc(100% - 20px); top: 8px; padding: 5px 8px; border-radius: 15px; }
    .chemistry-top-nav .nav-auth .app-account-chip { grid-template-columns: 24px; padding: 3px; }
    .chemistry-top-nav .nav-auth .app-account-avatar { width: 24px; height: 24px; border-radius: 8px; }
    .chemistry-top-nav .nav-auth .app-account-avatar-wrap { width: 24px; height: 24px; }
    .chemistry-top-nav .nav-auth .app-account-copy { display: none; }
    .chemistry-top-nav .nav-auth .app-account-chip.account-type-vip-student {
        grid-template-columns: 24px minmax(0, auto);
        padding-right: 6px;
    }
    .chemistry-top-nav .nav-auth .app-account-chip.account-type-vip-student .app-account-copy { display: block; }
    .chemistry-top-nav .nav-auth .app-account-chip.account-type-vip-student .app-account-copy strong { display: none; }
    .chemistry-top-nav .nav-auth .app-account-chip.account-type-vip-student .account-role-label { font-size: 0; }
    .chemistry-top-nav .nav-auth .app-account-chip.account-type-vip-student .account-role-label::after {
        content: "VIP";
        font-size: 7px;
        line-height: 1;
    }
    .chemistry-top-nav > .nav-container > .physics-text-size-switch .physics-text-size-trigger { width: auto; }
    .chemistry-top-nav .nav-auth { flex: 0 0 auto; max-width: none; overflow: visible; }
    .chemistry-top-nav .nav-auth .nav-admin-quick { width: auto; min-width: 40px; padding: 0 7px; font-size: 9px; }
    .chemistry-top-nav .nav-auth .nav-question-admin { min-width: 48px; }
    .chemistry-top-nav .nav-auth .nav-admin-label { display: none; }
    .chemistry-top-nav .nav-auth .nav-admin-label-compact { display: inline; }
}

@media (max-width: 520px) {
    .chemistry-top-nav .logo-text { display: none; }
}

@media (max-height: 700px) and (min-width: 769px) {
    .chemistry-hero-inner { padding-top: 74px; }
    .chemistry-hero-layout { min-height: 380px; }
    .chemistry-subject-switcher { margin-bottom: 13px; }
    .chemistry-brand-lockup { margin-bottom: 12px; }
    .chemistry-brand-lockup h1 { font-size: 64px; }
    .chemistry-hero-kicker { font-size: 25px; }
    .ph-system-page .chemistry-hero-action { min-height: 41px !important; }
    .chemistry-hero-stats { margin-top: 18px; }
}

@media (prefers-reduced-motion: reduce) {
    .chemistry-hero::before,
    .chemistry-hero-ambient,
    .chemistry-subject-switcher,
    .chemistry-brand-lockup .app-nav-mark,
    .chemistry-brand-lockup h1,
    .chemistry-hero-kicker,
    .chemistry-hero-actions,
    .chemistry-hero-stats {
        animation: none !important;
        opacity: 1;
        transform: none;
    }

    .chemistry-scene {
        animation: none !important;
        opacity: var(--chemistry-scene-opacity);
        transform: none;
    }

    .chemistry-molecule-main {
        animation: none !important;
        opacity: .72;
        transform: translate3d(132px, 14px, 0) scale(.82);
    }

    .chemistry-bubble,
    .chemistry-reaction-trail-live,
    .chemistry-glow-point,
    .chemistry-electron-satellite {
        animation: none !important;
        opacity: .34;
    }

    .chemistry-scene svg { transform: none !important; }
}

.chemistry-learning-nav[hidden],
.chemistry-learning-tab[hidden] { display: none !important; }
.chemistry-learning-nav {
    position: relative;
    display: flex;
    align-items: center;
    gap: 3px;
    margin-left: 5px;
    padding-left: 14px;
}
.chemistry-learning-nav::before {
    content: '';
    position: absolute;
    left: 3px;
    width: 1px;
    height: 22px;
    background: color-mix(in srgb, var(--ph-chrome-accent) 24%, var(--ph-line));
}
.chemistry-learning-tab {
    min-height: 40px;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 7px;
    padding: 8px 12px;
    border-radius: 11px;
    color: var(--ph-chrome-accent-hover);
    font-size: calc(13px + var(--ph-type-shift));
    font-weight: 720;
    letter-spacing: -.01em;
    text-decoration: none;
    white-space: nowrap;
    transition: color var(--ph-motion-panel) ease, background-color var(--ph-motion-panel) ease, box-shadow var(--ph-motion-panel) ease;
}
.chemistry-learning-tab svg {
    width: 24px;
    height: 18px;
    flex: 0 0 24px;
    fill: none;
    stroke: currentColor;
    stroke-width: 1.8;
    stroke-linecap: round;
    stroke-linejoin: round;
}
.chemistry-learning-tab .learning-label-compact { display: none; }
.chemistry-learning-tab:hover {
    color: var(--ph-chrome-accent-hover);
    background: var(--ph-chrome-accent-soft);
    box-shadow: inset 0 0 0 1px color-mix(in srgb, var(--ph-chrome-accent) 13%, transparent);
}
.chemistry-learning-tab:focus-visible {
    outline: 3px solid color-mix(in srgb, var(--ph-chrome-accent) 48%, var(--ph-surface));
    outline-offset: 2px;
}

@media (max-width: 760px) {
    .chemistry-learning-nav { gap: 2px; margin-left: 2px; padding-left: 10px; }
    .chemistry-learning-nav::before { left: 1px; }
    .chemistry-learning-tab { min-height: 44px; padding: 8px 9px; }
}

@media (max-width: 620px) {
    .chemistry-level-tabs-inner {
        width: calc(100vw - 20px);
        max-width: calc(100vw - 20px);
        display: grid;
        grid-template-columns: repeat(6, minmax(0, 1fr));
        gap: 3px;
    }
    .chemistry-level-tab { grid-column: span 2; min-width: 0; padding-inline: 5px; }
    .chemistry-learning-nav {
        grid-column: 1 / -1;
        display: grid;
        grid-template-columns: minmax(0, 1fr);
        gap: 3px;
        margin: 0;
        padding: 5px 0 0;
        border-top: 1px solid color-mix(in srgb, var(--ph-chrome-accent) 15%, var(--ph-line));
    }
    .chemistry-learning-nav::before { display: none; }
    .chemistry-learning-tab { width: 100%; min-width: 0; min-height: 44px; gap: 5px; padding: 7px 4px; font-size: calc(10px + var(--ph-type-shift)); }
    .chemistry-learning-tab svg { width: 23px; height: 18px; flex-basis: 23px; }
    .chemistry-learning-tab .learning-label-full { display: none; }
    .chemistry-learning-tab .learning-label-compact { display: inline; min-width: 0; overflow: hidden; text-overflow: ellipsis; }
    .chemistry-learning-tab { grid-column: 1 / -1; }
    .chemistry-level { scroll-margin-top: 190px; }
}