:root {
    color-scheme: light;
    --ink: #172027;
    --muted: #53626b;
    --line: #d8e0e4;
    --paper: #ffffff;
    --canvas: #f3f7f8;
    --teal: #087f78;
    --orange: #d86d1f;
    --dark: #11171b;
}

* {
    box-sizing: border-box;
}

html {
    background: var(--canvas);
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
    color: var(--ink);
    line-height: 1.55;
}

body {
    margin: 0;
}

a {
    color: var(--teal);
    text-underline-offset: 0.18em;
}

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

.site-header {
    background: var(--dark);
    color: #ffffff;
    border-bottom: 4px solid var(--orange);
}

.header-inner,
main,
.footer-inner {
    width: min(100% - 32px, 880px);
    margin-inline: auto;
}

.header-inner {
    min-height: 76px;
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 24px;
}

.brand {
    display: flex;
    align-items: center;
    gap: 12px;
    color: #ffffff;
    text-decoration: none;
    font-weight: 700;
}

.brand img {
    width: 44px;
    height: 44px;
    border-radius: 8px;
}

nav {
    display: flex;
    gap: 20px;
}

nav a {
    color: #e7eef1;
    text-decoration: none;
    font-weight: 600;
}

nav a[aria-current="page"] {
    color: #ffffff;
    border-bottom: 2px solid var(--orange);
}

main {
    padding-block: 56px 72px;
}

.intro {
    display: grid;
    grid-template-columns: 104px 1fr;
    align-items: center;
    gap: 28px;
    margin-bottom: 48px;
}

.intro img {
    width: 104px;
    height: 104px;
    border-radius: 20px;
    box-shadow: 0 12px 28px rgb(23 32 39 / 18%);
}

h1,
h2,
h3 {
    line-height: 1.15;
}

h1 {
    margin: 0 0 8px;
    font-size: clamp(2rem, 5vw, 3.25rem);
}

h2 {
    margin: 0 0 14px;
    font-size: 1.35rem;
}

h3 {
    margin: 0 0 8px;
    font-size: 1.08rem;
}

p {
    margin: 0 0 16px;
}

.lede {
    max-width: 640px;
    color: var(--muted);
    font-size: 1.15rem;
}

.eyebrow {
    margin-bottom: 8px;
    color: var(--orange);
    font-size: 0.82rem;
    font-weight: 800;
    letter-spacing: 0.08em;
    text-transform: uppercase;
}

.section {
    padding-block: 30px;
    border-top: 1px solid var(--line);
}

.section-intro {
    max-width: 680px;
    color: var(--muted);
}

.subject-guide,
.mode-list {
    margin: 22px 0 0;
}

.subject-guide > div,
.mode-list > div {
    display: grid;
    grid-template-columns: minmax(170px, 0.8fr) minmax(0, 2fr);
    gap: 24px;
    padding-block: 18px;
    border-top: 1px solid var(--line);
}

.subject-guide > div:last-child,
.mode-list > div:last-child {
    border-bottom: 1px solid var(--line);
}

.subject-guide dt,
.mode-list dt {
    font-weight: 750;
}

.subject-guide dd,
.mode-list dd {
    margin: 0;
    color: var(--muted);
}

.feature-list article {
    padding-block: 18px;
    border-top: 1px solid var(--line);
}

.feature-list article:last-child {
    border-bottom: 1px solid var(--line);
}

.feature-list p {
    max-width: 760px;
    color: var(--muted);
}

.grid {
    display: grid;
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 16px;
}

.card {
    padding: 22px;
    background: var(--paper);
    border: 1px solid var(--line);
    border-radius: 8px;
}

.card p:last-child,
.section p:last-child {
    margin-bottom: 0;
}

.callout {
    padding: 20px 22px;
    background: #e7f4f2;
    border-left: 4px solid var(--teal);
}

.contact-link {
    display: inline-block;
    margin-top: 6px;
    padding: 11px 16px;
    background: var(--teal);
    color: #ffffff;
    border-radius: 6px;
    font-weight: 700;
    text-decoration: none;
}

.contact-link:hover {
    background: var(--orange);
    color: #ffffff;
}

ul {
    margin: 0;
    padding-left: 1.25rem;
}

li + li {
    margin-top: 9px;
}

footer {
    background: #e6ecef;
    color: var(--muted);
    border-top: 1px solid var(--line);
}

.footer-inner {
    min-height: 92px;
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 24px;
}

.footer-inner p {
    margin: 0;
}

.footer-links {
    display: flex;
    gap: 18px;
}

@media (max-width: 640px) {
    .header-inner,
    .footer-inner {
        align-items: flex-start;
        flex-direction: column;
        padding-block: 18px;
    }

    nav {
        width: 100%;
        justify-content: space-between;
    }

    main {
        padding-top: 36px;
    }

    .intro {
        grid-template-columns: 72px 1fr;
        gap: 18px;
    }

    .intro img {
        width: 72px;
        height: 72px;
        border-radius: 14px;
    }

    .grid {
        grid-template-columns: 1fr;
    }

    .subject-guide > div,
    .mode-list > div {
        grid-template-columns: 1fr;
        gap: 6px;
    }

    .footer-links {
        flex-wrap: wrap;
    }
}