:root {
    --bg: #ffffff;
    --surface: #f6f8fa;
    --text: #1f2328;
    --muted: #656d76;
    --accent: #c2653a;
    --accent2: #0969da;
    --border: #d0d7de;
    color-scheme: light;
}

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

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Helvetica, Arial, sans-serif;
    background: var(--bg);
    color: var(--text);
    line-height: 1.7;
    padding: 1.5rem;
    transition: background 0.2s ease, color 0.2s ease;
}

@media (min-width: 640px) {
    body { padding: 3rem 2rem; }
}

.container {
    max-width: 640px;
    margin: 0 auto;
}

/* Navigation */
nav {
    display: flex;
    gap: 1.2rem;
    margin-bottom: 1.2rem;
    font-size: 0.8rem;
    flex-wrap: wrap;
    align-items: center;
}


nav a {
    color: var(--muted);
    text-decoration: none;
    transition: color 0.2s;
    padding: 0.2rem 0;
}

nav a:hover, nav a.active {
    color: var(--accent);
}

/* Banner */
.banner {
    margin-bottom: 1.5rem;
    border-radius: 8px;
    overflow: hidden;
}

.banner img {
    width: 100%;
    display: block;
    height: 120px;
    object-fit: cover;
    object-position: center;
    opacity: 0.85;
}

@media (min-width: 640px) {
    .banner img { height: auto; }
}

/* Header */
header {
    margin-bottom: 2rem;
    padding-bottom: 1.2rem;
    border-bottom: 1px solid var(--border);
}

h1 {
    font-size: 1.5rem;
    font-weight: 600;
    color: var(--accent);
    letter-spacing: -0.03em;
}

@media (min-width: 640px) {
    h1 { font-size: 2rem; }
}

.subtitle {
    color: var(--muted);
    font-size: 0.85rem;
    margin-top: 0.2rem;
}

@media (min-width: 640px) {
    .subtitle { font-size: 0.95rem; }
}


/* Sections */
section {
    margin-bottom: 2rem;
}

h2 {
    font-size: 0.7rem;
    text-transform: uppercase;
    letter-spacing: 0.1em;
    color: var(--accent2);
    margin-bottom: 0.75rem;
    font-weight: 600;
}

p {
    color: var(--muted);
    margin-bottom: 0.75rem;
    font-size: 0.9rem;
}

@media (min-width: 640px) {
    p { font-size: 0.95rem; }
}

a {
    color: var(--accent2);
    text-decoration: none;
}

a:hover {
    text-decoration: underline;
}

/* Lists */
ul {
    list-style: none;
}

ul li {
    padding: 0.4rem 0;
    color: var(--muted);
    font-size: 0.9rem;
}

ul li a {
    color: var(--text);
    font-weight: 500;
}

ul li .meta {
    font-size: 0.75rem;
    color: var(--muted);
    display: block;
    margin-top: 0.1rem;
}

@media (min-width: 640px) {
    ul li .meta {
        display: inline;
        margin-top: 0;
        margin-left: 0.5rem;
    }
}

/* Back link (for sub-pages) */
.back {
    margin-bottom: 1.5rem;
    display: inline-block;
    font-size: 0.85rem;
}

/* Presentation pages */
.presentation-container {
    max-width: 100%;
    margin: 0;
    padding: 0;
}

.back-link {
    display: inline-block;
    padding: 1rem 2rem;
    color: var(--accent2);
    font-size: 0.9rem;
}

/* Tables — mobile overflow */
table {
    width: 100%;
    border-collapse: collapse;
    font-size: 0.9rem;
}

.container table {
    display: block;
    overflow-x: auto;
    -webkit-overflow-scrolling: touch;
}

th, td {
    padding: 0.4rem 0.75rem;
    text-align: left;
    border-bottom: 1px solid var(--border);
}

th {
    font-weight: 600;
    font-size: 0.85rem;
    color: var(--muted);
}