:root {
    color-scheme: light;

    --color-background: #fff;
    --color-text: #181818;
    --color-heading: #000;
    --color-ink: #111;
    --color-muted: #333;
    --color-border: #ccc;
    --color-border-soft: #d4d4d4;
    --color-border-strong: #777;
    --color-surface: #f5f5f5;
    --color-surface-hover: #ececec;
    --color-code-text: #f5f5f5;

    --font-family-sans: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
    --font-family-mono: "SFMono-Regular", Consolas, "Liberation Mono", monospace;
    --font-size-small: 0.9rem;
    --font-size-code: 0.92em;
    --font-size-card-title: 1.15rem;
    --font-size-site-title: 1.25rem;
    --font-weight-medium: 600;
    --font-weight-semibold: 650;
    --font-weight-bold: 750;

    font-family: var(--font-family-sans);
    color: var(--color-text);
    background: var(--color-background);
    line-height: 1.65;
}

* {
    box-sizing: border-box;
}

body {
    margin: 0;
    padding: 2rem 1rem;
}

.site-shell {
    width: 100%;
}

.site-header {
    display: flex;
    width: min(100%, 52rem);
    margin: 0 auto 1rem;
    align-items: center;
    justify-content: space-between;
    gap: 1rem 2rem;
}

.site-title {
    flex: none;
    color: var(--color-heading);
    font-size: var(--font-size-site-title);
    font-weight: var(--font-weight-bold);
    text-decoration: none;
}

.site-nav {
    display: flex;
    flex-wrap: wrap;
    justify-content: flex-end;
    gap: 0.35rem;
}

.site-nav a {
    padding: 0.4rem 0.65rem;
    color: var(--color-ink);
    border-radius: 0.2rem;
    font-size: var(--font-size-small);
    font-weight: var(--font-weight-medium);
    text-decoration: none;
}

.site-nav a:hover {
    color: var(--color-heading);
    background: var(--color-surface-hover);
}

.site-nav a[aria-current="page"] {
    color: var(--color-background);
    background: var(--color-ink);
}

.document {
    width: min(100%, 52rem);
    margin: 0 auto;
    padding: clamp(1.5rem, 4vw, 3rem);
    background: var(--color-background);
    border: 1px solid var(--color-border-soft);
    border-radius: 0.25rem;
}

h1,
h2,
h3 {
    color: var(--color-heading);
    line-height: 1.25;
}

h1 {
    margin-top: 0;
    padding-bottom: 0.75rem;
    border-bottom: 2px solid var(--color-ink);
}

a {
    color: var(--color-heading);
}

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

.feature-list {
    padding-left: 1.25rem;
}

.resource-list,
.exercise-list {
    display: grid;
    margin: 0;
    padding: 0;
    gap: 0.75rem;
    list-style: none;
}

.resource-list li + li {
    margin-top: 0;
}

.resource-list a,
.exercise-card {
    display: block;
    padding: 1rem 1.1rem;
    border: 1px solid var(--color-border-strong);
    border-radius: 0.25rem;
    background: var(--color-surface);
    box-shadow: 0 3px 0 var(--color-ink);
}

.resource-list a {
    font-weight: var(--font-weight-semibold);
    text-decoration: none;
}

.resource-list a:hover {
    border-color: var(--color-ink);
    background: var(--color-surface-hover);
}

.exercise-card h2 {
    margin-top: 0;
    font-size: var(--font-size-card-title);
}

.exercise-card h2 a {
    text-decoration: none;
}

.exercise-card ul {
    margin-bottom: 0;
}

.empty-state {
    margin: 1.5rem 0 0;
    padding: 1.25rem;
    color: var(--color-muted);
    background: var(--color-background);
    border: 1px dashed var(--color-border-strong);
    border-radius: 0.25rem;
    text-align: center;
}

.contact {
    margin-top: 2rem;
    padding-top: 1.25rem;
    border-top: 1px solid var(--color-border);
}

pre {
    overflow-x: auto;
    padding: 1rem;
    color: var(--color-code-text);
    background: var(--color-ink);
    border-radius: 0.25rem;
}

code {
    font-family: var(--font-family-mono);
    font-size: var(--font-size-code);
}

:not(pre) > code {
    padding: 0.15em 0.35em;
    color: var(--color-ink);
    background: var(--color-surface-hover);
    border-radius: 0.15rem;
}

li + li {
    margin-top: 0.35rem;
}

@media (max-width: 40rem) {
    body {
        padding: 0;
    }

    .site-header {
        margin-bottom: 0;
        padding: 1rem 1.25rem;
        align-items: flex-start;
        flex-direction: column;
    }

    .site-nav {
        justify-content: flex-start;
    }

    .document {
        border: 0;
        border-radius: 0;
        box-shadow: none;
    }
}