:root {
    color-scheme: light dark;
    --page: #eef4f3;
    --surface: #ffffff;
    --surface-muted: #e5efed;
    --text: #18302f;
    --text-muted: #58706e;
    --heading: #0c5654;
    --accent: #d9664a;
    --accent-hover: #b94f38;
    --header-start: #087f79;
    --header-end: #075454;
    --footer: #123b3a;
    --border: #c9ddda;
    --shadow: rgba(12, 64, 62, 0.14);
    --focus: #f1a24e;
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html {
    scroll-behavior: smooth;
}

body {
    font-family: "Avenir Next", "Segoe UI", sans-serif;
    line-height: 1.7;
    color: var(--text);
    background: var(--page);
    min-height: 100vh;
    padding: clamp(16px, 4vw, 48px) clamp(12px, 3vw, 28px);
    -webkit-font-smoothing: antialiased;
}

body::before {
    background: linear-gradient(135deg, rgba(8, 127, 121, 0.09), transparent 42%);
    content: "";
    inset: 0;
    pointer-events: none;
    position: fixed;
    z-index: -1;
}

.container {
    max-width: 1024px;
    margin: 0 auto;
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: 20px;
    box-shadow: 0 24px 70px var(--shadow);
    overflow: hidden;
}

header {
    background: linear-gradient(120deg, var(--header-start), var(--header-end));
    color: #f5fffd;
    padding: clamp(30px, 5vw, 54px) clamp(22px, 6vw, 72px);
    position: relative;
}

header::after {
    border: 1px solid rgba(255, 255, 255, 0.2);
    border-radius: 50%;
    content: "";
    height: 180px;
    position: absolute;
    right: -70px;
    top: -90px;
    width: 180px;
}

.header-content {
    align-items: center;
    display: flex;
    gap: 18px;
    max-width: 680px;
    position: relative;
    z-index: 1;
}

.app-icon {
    border: 3px solid rgba(255, 255, 255, 0.8);
    border-radius: 18px;
    box-shadow: 0 8px 20px rgba(0, 0, 0, 0.18);
    flex: 0 0 auto;
    height: 72px;
    width: 72px;
}

header p {
    color: rgba(245, 255, 253, 0.78);
    margin-bottom: 0;
}

h1,
h2,
h3,
h4 {
    line-height: 1.2;
}

h1 {
    font-size: clamp(1.8rem, 4vw, 2.5rem);
    font-weight: 750;
    letter-spacing: 0;
    margin-bottom: 8px;
}

h2 {
    color: var(--heading);
    font-size: clamp(1.3rem, 2.5vw, 1.7rem);
    margin: 0 0 16px;
    padding-bottom: 10px;
    border-bottom: 2px solid var(--border);
}

h3 {
    color: var(--heading);
    font-size: 1.12rem;
    margin: 26px 0 10px;
}

h4 {
    color: var(--text-muted);
    font-size: 0.98rem;
    margin: 22px 0 8px;
}

main {
    padding: clamp(24px, 5vw, 52px) clamp(20px, 7vw, 80px);
}

nav#table-of-contents {
    background: var(--surface-muted);
    border: 1px solid var(--border);
    border-radius: 14px;
    margin-bottom: 48px;
    padding: 22px 24px;
}

nav#table-of-contents h2 {
    border-bottom: 0;
    font-size: 1.15rem;
    margin: 0 0 14px;
    padding-bottom: 0;
}

nav#table-of-contents ul {
    columns: 2;
    column-gap: 32px;
    list-style: none;
    margin: 0;
}

nav#table-of-contents li {
    break-inside: avoid;
    margin-bottom: 5px;
}

nav#table-of-contents a {
    color: var(--heading);
    display: inline-block;
    font-weight: 650;
    padding: 3px 0;
    text-decoration: none;
    transition: color 160ms ease, transform 160ms ease;
}

nav#table-of-contents a:hover {
    color: var(--accent-hover);
    transform: translateX(3px);
}

nav#table-of-contents.safety-toc {
    margin-bottom: 24px;
}

section {
    border-top: 1px solid var(--border);
    margin-bottom: 42px;
    padding-top: 30px;
    scroll-margin-top: 20px;
}

section:first-of-type {
    border-top: 0;
    padding-top: 0;
}

section.safety-notice {
    background: #fff2d8;
    border: 2px solid #b95427;
    border-left-width: 8px;
    border-radius: 8px;
    margin: 0 0 32px;
    padding: 20px 24px;
}

section.safety-notice h2 {
    border-bottom: 1px solid #e6bd75;
    color: #74320f;
    margin-bottom: 12px;
}

section.safety-notice p {
    color: #402b18;
}

section.safety-notice p:last-child {
    margin-bottom: 0;
}

p {
    color: var(--text);
    margin-bottom: 14px;
    max-width: 78ch;
}

ul {
    margin: 0 0 16px 22px;
    max-width: 78ch;
}

li {
    margin-bottom: 9px;
    padding-left: 4px;
}

strong {
    color: var(--heading);
    font-weight: 700;
}

a {
    color: var(--accent-hover);
    text-decoration-thickness: 1px;
    text-underline-offset: 3px;
    transition: color 160ms ease;
}

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

a:focus-visible {
    border-radius: 3px;
    outline: 3px solid var(--focus);
    outline-offset: 3px;
}

footer {
    background: var(--footer);
    color: rgba(245, 255, 253, 0.78);
    padding: 20px 28px;
    text-align: center;
    font-size: 0.88rem;
}

footer p {
    color: inherit;
    margin: 0 auto;
}

@media (prefers-color-scheme: dark) {
    :root {
        --page: #0d1f1e;
        --surface: #142827;
        --surface-muted: #1a3533;
        --text: #d9e9e6;
        --text-muted: #9ebbb7;
        --heading: #83d7cd;
        --accent: #f29a69;
        --accent-hover: #ffb181;
        --header-start: #096c68;
        --header-end: #073e40;
        --footer: #0a1919;
        --border: #2b4b48;
        --shadow: rgba(0, 0, 0, 0.35);
        --focus: #ffd166;
    }
}

@media (max-width: 640px) {
    body {
        padding: 0;
    }

    .container {
        border: 0;
        border-radius: 0;
        min-height: 100vh;
    }

    header {
        padding: 28px 20px;
    }

    .header-content {
        align-items: flex-start;
        gap: 14px;
    }

    .app-icon {
        border-radius: 14px;
        height: 56px;
        width: 56px;
    }

    h1 {
        font-size: 1.65rem;
    }

    main {
        padding: 28px 20px;
    }

    nav#table-of-contents {
        margin-bottom: 34px;
        padding: 18px;
    }

    nav#table-of-contents ul {
        columns: 1;
    }

    section {
        margin-bottom: 32px;
        padding-top: 24px;
    }

    p,
    li {
        font-size: 0.97rem;
    }
}

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

    *,
    *::before,
    *::after {
        transition-duration: 0.01ms !important;
    }
}