:root {
    color-scheme: dark;
    --bg: #070a14;
    --ink: #f7f8ff;
    --muted: rgba(238, 242, 255, 0.62);
    --faint: rgba(238, 242, 255, 0.34);
    --line: rgba(255, 255, 255, 0.15);
    --cyan: #7dd3fc;
    --violet: #a5b4fc;
    --coral: #ffb38c;
    --acid: #d9ff83;
    --ease: cubic-bezier(0.22, 0.9, 0.3, 1);
}

* {
    box-sizing: border-box;
}

html {
    min-height: 100%;
    background: var(--bg);
    scroll-behavior: smooth;
}

body {
    min-width: 320px;
    min-height: 100vh;
    margin: 0;
    overflow-x: clip;
    color: var(--ink);
    background: var(--bg);
    font-family: "Inter", "SF Pro Display", "Segoe UI", "Microsoft YaHei", "PingFang SC", sans-serif;
    -webkit-font-smoothing: antialiased;
    text-rendering: optimizeLegibility;
}

a {
    color: inherit;
    text-decoration: none;
}

::selection {
    color: #07111d;
    background: var(--cyan);
}

:focus-visible {
    outline: 2px solid var(--cyan);
    outline-offset: 4px;
}

.sr-only {
    position: absolute;
    width: 1px;
    height: 1px;
    padding: 0;
    margin: -1px;
    overflow: hidden;
    clip: rect(0, 0, 0, 0);
    white-space: nowrap;
    border: 0;
}

.skip-link {
    position: fixed;
    top: 10px;
    left: 12px;
    z-index: 100;
    padding: 10px 15px;
    border-radius: 999px;
    color: #07111d;
    background: #fff;
    transform: translateY(-160%);
    transition: transform 180ms ease;
}

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

.experiment-nav {
    position: fixed;
    top: max(16px, env(safe-area-inset-top));
    left: 50%;
    z-index: 60;
    display: grid;
    grid-template-columns: 1fr auto 1fr;
    align-items: center;
    width: min(1120px, calc(100% - 32px));
    min-height: 54px;
    padding: 7px 10px;
    border: 1px solid var(--line);
    border-radius: 999px;
    background: rgba(8, 12, 24, 0.64);
    box-shadow: inset 0 1px 0 rgba(255, 255, 255, 0.12), 0 18px 48px rgba(0, 0, 0, 0.28);
    backdrop-filter: blur(18px) saturate(1.35);
    -webkit-backdrop-filter: blur(18px) saturate(1.35);
    transform: translateX(-50%);
}

.back-link {
    display: inline-flex;
    width: fit-content;
    min-height: 40px;
    align-items: center;
    gap: 9px;
    padding: 0 14px;
    border-radius: 999px;
    color: rgba(238, 242, 255, 0.76);
    font-size: 0.84rem;
    font-weight: 650;
    transition: color 180ms ease, background 180ms ease, transform 180ms var(--ease);
}

.back-link:hover,
.back-link:focus-visible {
    color: var(--ink);
    background: rgba(255, 255, 255, 0.1);
    transform: translateX(-2px);
}

.nav-title,
.nav-index {
    margin: 0;
    font-size: 0.68rem;
    font-weight: 750;
    letter-spacing: 0.16em;
    text-transform: uppercase;
}

.nav-title {
    display: flex;
    align-items: center;
    gap: 9px;
    color: rgba(238, 242, 255, 0.74);
}

.nav-title i {
    width: 6px;
    height: 6px;
    border-radius: 50%;
    background: var(--cyan);
    box-shadow: 0 0 14px rgba(125, 211, 252, 0.95);
}

.nav-index {
    justify-self: end;
    padding-right: 14px;
    color: var(--faint);
}

.progress-rail {
    position: fixed;
    top: 50%;
    right: max(22px, env(safe-area-inset-right));
    z-index: 55;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 9px;
    color: rgba(255, 255, 255, 0.42);
    font-size: 0.54rem;
    font-weight: 750;
    letter-spacing: 0.12em;
    transform: translateY(-50%);
}

.progress-rail > i {
    position: relative;
    display: block;
    width: 1px;
    height: min(34vh, 230px);
    overflow: hidden;
    background: rgba(255, 255, 255, 0.18);
}

.progress-rail b {
    position: absolute;
    inset: 0;
    display: block;
    background: linear-gradient(180deg, var(--cyan), var(--violet), var(--coral));
    transform: scaleY(0);
    transform-origin: top;
    will-change: transform;
}

.progress-readout {
    position: fixed;
    right: max(52px, calc(env(safe-area-inset-right) + 30px));
    bottom: max(24px, env(safe-area-inset-bottom));
    z-index: 55;
    color: rgba(255, 255, 255, 0.56);
    font-size: 0.66rem;
    font-weight: 760;
    letter-spacing: 0.15em;
    font-variant-numeric: tabular-nums;
}

.chapter {
    position: relative;
    height: 210svh;
}

.stage {
    position: sticky;
    top: 0;
    display: grid;
    place-items: center;
    width: 100%;
    height: 100svh;
    min-height: 620px;
    overflow: hidden;
    isolation: isolate;
}

.stage::before,
.stage::after {
    content: "";
    position: absolute;
    z-index: -3;
    border-radius: 50%;
    filter: blur(3px);
    pointer-events: none;
}

.stage::before {
    width: min(60vw, 780px);
    aspect-ratio: 1;
    top: -33%;
    right: -12%;
    opacity: 0.3;
    background: radial-gradient(circle, var(--glow-a), transparent 68%);
}

.stage::after {
    width: min(48vw, 620px);
    aspect-ratio: 1;
    bottom: -30%;
    left: -9%;
    opacity: 0.22;
    background: radial-gradient(circle, var(--glow-b), transparent 68%);
}

.chapter-velocity .stage {
    --glow-a: rgba(92, 220, 255, 0.7);
    --glow-b: rgba(107, 92, 255, 0.68);
    background: radial-gradient(circle at 24% 70%, #0d2139, transparent 38%), #070a14;
}

.chapter-tension .stage {
    --glow-a: rgba(165, 180, 252, 0.72);
    --glow-b: rgba(240, 171, 252, 0.65);
    background: radial-gradient(circle at 82% 28%, #251937, transparent 42%), #080912;
}

.chapter-grid .stage {
    --glow-a: rgba(255, 179, 140, 0.72);
    --glow-b: rgba(255, 104, 98, 0.55);
    background: radial-gradient(circle at 46% 56%, #2b161a, transparent 45%), #09090e;
}

.chapter-rhythm .stage {
    --glow-a: rgba(217, 255, 131, 0.62);
    --glow-b: rgba(125, 211, 252, 0.58);
    background: radial-gradient(circle at 50% 48%, #1b291f, transparent 44%), #070b0b;
}

.stage-grid {
    position: absolute;
    inset: 0;
    z-index: -2;
    opacity: 0.28;
    pointer-events: none;
    background-image:
        linear-gradient(rgba(255, 255, 255, 0.07) 1px, transparent 1px),
        linear-gradient(90deg, rgba(255, 255, 255, 0.07) 1px, transparent 1px);
    background-size: clamp(54px, 7vw, 108px) clamp(54px, 7vw, 108px);
    mask-image: linear-gradient(180deg, transparent 4%, #000 28%, #000 72%, transparent 96%);
    -webkit-mask-image: linear-gradient(180deg, transparent 4%, #000 28%, #000 72%, transparent 96%);
}

.chapter-meta {
    position: absolute;
    top: clamp(108px, 15vh, 154px);
    left: max(28px, calc((100vw - 1120px) / 2));
    right: max(58px, calc((100vw - 1120px) / 2));
    display: flex;
    justify-content: space-between;
    gap: 24px;
    color: var(--muted);
}

.chapter-meta p {
    margin: 0;
    font-size: clamp(0.64rem, 0.8vw, 0.76rem);
    font-weight: 650;
    letter-spacing: 0.12em;
    text-transform: uppercase;
}

.chapter-meta span {
    margin-right: 12px;
    color: var(--chapter-accent, var(--cyan));
}

.chapter-note {
    position: absolute;
    left: max(28px, calc((100vw - 1120px) / 2));
    bottom: clamp(34px, 7vh, 72px);
    width: min(360px, calc(100% - 100px));
    margin: 0;
    color: var(--muted);
    font-size: clamp(0.85rem, 1.1vw, 1rem);
    line-height: 1.75;
}

.scroll-hint {
    position: absolute;
    right: max(56px, calc((100vw - 1120px) / 2));
    bottom: clamp(34px, 7vh, 72px);
    display: flex;
    align-items: center;
    gap: 10px;
    margin: 0;
    color: var(--faint);
    font-size: 0.58rem;
    font-weight: 750;
    letter-spacing: 0.16em;
}

.scroll-hint i {
    position: relative;
    width: 42px;
    height: 1px;
    overflow: hidden;
    background: rgba(255, 255, 255, 0.18);
}

.scroll-hint i::after {
    content: "";
    position: absolute;
    inset: 0;
    background: var(--cyan);
    animation: scan 1.5s ease-in-out infinite;
}

@keyframes scan {
    from { transform: translateX(-105%); }
    to { transform: translateX(105%); }
}

.type-stack {
    position: relative;
    z-index: 2;
    display: flex;
    width: 100%;
    flex-direction: column;
    align-items: center;
    font-weight: 900;
    line-height: 0.75;
    letter-spacing: -0.075em;
    text-align: center;
    text-transform: uppercase;
}

.type-stack span {
    display: block;
    white-space: nowrap;
    transform-origin: center;
    will-change: transform, letter-spacing, opacity;
}

.velocity-stack {
    font-size: clamp(4.6rem, 15.5vw, 15.5rem);
}

.velocity-stack span:nth-child(1) {
    color: var(--ink);
}

.velocity-stack span:nth-child(2) {
    color: transparent;
    -webkit-text-stroke: 1.5px rgba(125, 211, 252, 0.72);
}

.velocity-stack span:nth-child(3) {
    color: var(--cyan);
}

.chapter-tension {
    --chapter-accent: var(--violet);
}

.tension-stack {
    font-size: clamp(4rem, 13.8vw, 14rem);
}

.tension-stack span:nth-child(1) {
    color: var(--violet);
}

.tension-stack span:nth-child(2) {
    color: transparent;
    -webkit-text-stroke: 1.5px rgba(247, 248, 255, 0.82);
}

.tension-stack span:nth-child(3) {
    color: var(--ink);
}

.axis-readout {
    position: absolute;
    right: max(56px, calc((100vw - 1120px) / 2));
    bottom: clamp(38px, 7vh, 76px);
    display: grid;
    grid-template-columns: auto minmax(100px, 14vw) 34px;
    align-items: center;
    gap: 10px;
    color: var(--faint);
    font-size: 0.58rem;
    font-weight: 760;
    letter-spacing: 0.12em;
    font-variant-numeric: tabular-nums;
}

.axis-readout i {
    display: block;
    height: 2px;
    overflow: hidden;
    background: rgba(255, 255, 255, 0.18);
}

.axis-readout b {
    display: block;
    width: 100%;
    height: 100%;
    background: linear-gradient(90deg, var(--violet), #f0abfc);
    transform: scaleX(0.5);
    transform-origin: left;
    will-change: transform;
}

.chapter-grid {
    --chapter-accent: var(--coral);
}

.scatter-field {
    position: relative;
    z-index: 2;
    width: min(1160px, 94vw);
    height: min(58vh, 590px);
}

.scatter-field span {
    position: absolute;
    top: 50%;
    left: 50%;
    display: block;
    color: var(--ink);
    font-size: clamp(4.5rem, 15vw, 14.5rem);
    font-weight: 900;
    line-height: 0.75;
    letter-spacing: -0.08em;
    text-transform: uppercase;
    transform: translate(-50%, -50%);
    transform-origin: center;
    will-change: transform, color, opacity;
}

.scatter-field span:nth-child(2) {
    color: transparent;
    -webkit-text-stroke: 1.5px var(--coral);
}

.scatter-field span:nth-child(3) {
    color: var(--coral);
}

.orbit-mark {
    position: absolute;
    left: 50%;
    top: 50%;
    z-index: 1;
    width: min(52vw, 660px);
    aspect-ratio: 1;
    border: 1px solid rgba(255, 179, 140, 0.18);
    border-radius: 50%;
    transform: translate(-50%, -50%);
}

.orbit-mark::before,
.orbit-mark::after {
    content: "";
    position: absolute;
    background: rgba(255, 179, 140, 0.2);
}

.orbit-mark::before {
    top: 50%;
    left: -8%;
    width: 116%;
    height: 1px;
}

.orbit-mark::after {
    top: -8%;
    left: 50%;
    width: 1px;
    height: 116%;
}

.orbit-mark i,
.orbit-mark b {
    position: absolute;
    width: 7px;
    height: 7px;
    border-radius: 50%;
    background: var(--coral);
    box-shadow: 0 0 18px rgba(255, 179, 140, 0.9);
}

.orbit-mark i {
    top: 18%;
    left: 6%;
}

.orbit-mark b {
    right: 6%;
    bottom: 18%;
}

.chapter-rhythm {
    --chapter-accent: var(--acid);
}

.rhythm-field {
    position: relative;
    z-index: 2;
    width: min(1180px, 94vw);
    height: min(60vh, 610px);
}

.rhythm-field span {
    position: absolute;
    top: 50%;
    left: 50%;
    display: block;
    color: var(--ink);
    font-size: clamp(3.8rem, 12.5vw, 12rem);
    font-weight: 900;
    line-height: 0.8;
    letter-spacing: -0.075em;
    white-space: nowrap;
    text-transform: uppercase;
    transform: translate(-50%, -50%);
    transform-origin: center;
    will-change: transform, opacity, color;
}

.rhythm-field span:nth-child(2) {
    color: transparent;
    -webkit-text-stroke: 1.5px rgba(217, 255, 131, 0.9);
}

.rhythm-field span:nth-child(3) {
    color: var(--acid);
}

.rhythm-beat {
    position: absolute;
    right: max(56px, calc((100vw - 1120px) / 2));
    bottom: clamp(38px, 7vh, 76px);
    margin: 0;
    color: rgba(217, 255, 131, 0.48);
    font-size: 0.62rem;
    font-weight: 760;
    letter-spacing: 0.22em;
}

.next-experiment {
    display: grid;
    grid-template-columns: minmax(0, 0.9fr) minmax(340px, 1.1fr);
    gap: clamp(44px, 9vw, 130px);
    align-content: center;
    min-height: 100svh;
    padding: 140px max(28px, calc((100vw - 1120px) / 2)) 72px;
    border-top: 1px solid var(--line);
    background:
        radial-gradient(circle at 86% 48%, rgba(125, 211, 252, 0.15), transparent 32%),
        radial-gradient(circle at 16% 70%, rgba(165, 180, 252, 0.13), transparent 35%),
        #070a14;
}

.eyebrow {
    margin: 0 0 20px;
    color: var(--cyan);
    font-size: 0.65rem;
    font-weight: 760;
    letter-spacing: 0.18em;
}

.next-experiment h2 {
    margin: 0;
    font-size: clamp(2.8rem, 6.2vw, 6.7rem);
    font-weight: 820;
    line-height: 0.96;
    letter-spacing: -0.065em;
}

.next-experiment h2 span {
    color: rgba(247, 248, 255, 0.42);
}

.next-link {
    align-self: center;
    display: grid;
    gap: 18px;
    padding: clamp(28px, 4vw, 50px);
    border: 1px solid rgba(125, 211, 252, 0.28);
    border-radius: 28px;
    background: rgba(255, 255, 255, 0.045);
    box-shadow: inset 0 1px 0 rgba(255, 255, 255, 0.08);
    transition: border-color 240ms ease, background 240ms ease, transform 240ms var(--ease);
}

.next-link:hover,
.next-link:focus-visible {
    border-color: rgba(125, 211, 252, 0.65);
    background: rgba(125, 211, 252, 0.08);
    transform: translateY(-5px);
}

.next-link > span,
.next-link em {
    color: var(--muted);
    font-size: 0.65rem;
    font-style: normal;
    font-weight: 700;
    letter-spacing: 0.15em;
}

.next-link strong {
    color: var(--ink);
    font-size: clamp(3rem, 7.5vw, 7.5rem);
    font-weight: 900;
    line-height: 0.8;
    letter-spacing: -0.075em;
}

.next-link em {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.next-link em i {
    color: var(--cyan);
    font-size: 1.25rem;
    font-style: normal;
    transition: transform 220ms var(--ease);
}

.next-link:hover em i,
.next-link:focus-visible em i {
    transform: translateX(6px);
}

.all-link {
    width: fit-content;
    color: var(--muted);
    font-size: 0.74rem;
    font-weight: 650;
    text-decoration: underline;
    text-decoration-color: rgba(255, 255, 255, 0.28);
    text-underline-offset: 5px;
}

.noscript {
    position: fixed;
    inset: auto 16px 16px;
    z-index: 100;
    margin: 0;
    padding: 12px 16px;
    border: 1px solid var(--line);
    border-radius: 12px;
    color: var(--ink);
    background: #111525;
    font-size: 0.8rem;
    text-align: center;
}

@media (max-width: 760px) {
    .experiment-nav {
        width: calc(100% - 22px);
        min-height: 50px;
        padding: 5px 7px;
    }

    .back-link {
        min-height: 38px;
        padding: 0 10px;
        font-size: 0.75rem;
    }

    .nav-title {
        font-size: 0;
    }

    .nav-title i {
        width: 7px;
        height: 7px;
    }

    .nav-index {
        padding-right: 10px;
        font-size: 0.62rem;
    }

    .progress-rail {
        right: 10px;
    }

    .progress-readout {
        right: 24px;
        bottom: max(18px, env(safe-area-inset-bottom));
    }

    .chapter {
        height: 190svh;
    }

    .stage {
        min-height: 540px;
    }

    .chapter-meta {
        top: 102px;
        left: 20px;
        right: 34px;
    }

    .chapter-meta p:last-child {
        display: none;
    }

    .chapter-note {
        left: 20px;
        bottom: max(28px, calc(env(safe-area-inset-bottom) + 18px));
        width: min(290px, calc(100% - 70px));
        font-size: 0.8rem;
    }

    .scroll-hint,
    .axis-readout,
    .rhythm-beat {
        display: none;
    }

    .velocity-stack {
        font-size: clamp(4rem, 21vw, 8.8rem);
    }

    .tension-stack {
        font-size: clamp(3.6rem, 18.5vw, 8rem);
    }

    .scatter-field,
    .rhythm-field {
        width: calc(100vw - 28px);
        height: 54vh;
    }

    .scatter-field span {
        font-size: clamp(4rem, 22vw, 8rem);
    }

    .rhythm-field span {
        font-size: clamp(3.5rem, 18.5vw, 7rem);
    }

    .orbit-mark {
        width: min(78vw, 520px);
    }

    .next-experiment {
        grid-template-columns: 1fr;
        gap: 44px;
        padding: 126px 20px 58px;
    }

    .next-link {
        padding: 28px 24px;
        border-radius: 22px;
    }

    .next-link strong {
        font-size: clamp(3rem, 16vw, 5.2rem);
    }
}

@media (max-height: 620px) and (orientation: landscape) {
    .experiment-nav {
        top: 10px;
    }

    .stage {
        min-height: 0;
    }

    .chapter-meta {
        top: 80px;
    }

    .chapter-note {
        bottom: 22px;
    }

    .velocity-stack,
    .tension-stack {
        font-size: min(17vh, 8.7rem);
        line-height: 0.78;
    }

    .scatter-field,
    .rhythm-field {
        height: 48vh;
    }

    .scatter-field span,
    .rhythm-field span {
        font-size: min(20vh, 8rem);
    }

    .progress-rail {
        display: none;
    }
}

@media (prefers-reduced-motion: reduce) {
    html {
        scroll-behavior: auto;
    }

    *,
    *::before,
    *::after {
        animation-duration: 0.01ms !important;
        animation-iteration-count: 1 !important;
        transition-duration: 0.01ms !important;
    }

    .chapter {
        height: auto;
    }

    .stage {
        position: relative;
        min-height: 100svh;
    }

    .type-stack span,
    .scatter-field span,
    .rhythm-field span {
        opacity: 1 !important;
        transform: none !important;
    }

    .scatter-field,
    .rhythm-field {
        display: flex;
        height: auto;
        flex-direction: column;
        align-items: center;
        justify-content: center;
        gap: 0.08em;
    }

    .scatter-field span,
    .rhythm-field span {
        position: static;
    }

    .scroll-hint {
        display: none;
    }
}