/* ===== Reset & Base ===== */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

body {
    font-family: system-ui, -apple-system, 'Segoe UI', Roboto, sans-serif;
    line-height: 1.6;
    color: #1a1a2e;
    background: #f8f9fa;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

/* ===== Header / Nav ===== */
header {
    background: #1a1a2e;
    color: #fff;
    padding: 1rem 2rem;
}

nav {
    max-width: 900px;
    margin: 0 auto;
    display: flex;
    align-items: center;
    gap: 2rem;
}

.logo {
    font-size: 1.25rem;
    font-weight: 700;
    color: #fff;
    text-decoration: none;
    letter-spacing: -0.02em;
}

.nav-links {
    display: flex;
    gap: 1.25rem;
}

.nav-links a {
    color: #a8b2d1;
    text-decoration: none;
    font-size: 0.925rem;
    transition: color 0.2s;
}

.nav-links a:hover { color: #fff; }

/* ===== Main content ===== */
main {
    flex: 1;
    max-width: 900px;
    margin: 0 auto;
    padding: 2rem;
    width: 100%;
}

/* ===== Hero ===== */
.hero {
    text-align: center;
    padding: 4rem 0 3rem;
}

.hero h1 {
    font-size: 2.5rem;
    font-weight: 700;
    margin-bottom: 0.75rem;
}

.subtitle {
    font-size: 1.15rem;
    color: #555;
    margin-bottom: 2rem;
}

.btn {
    display: inline-block;
    padding: 0.7rem 1.8rem;
    background: #4361ee;
    color: #fff;
    text-decoration: none;
    border-radius: 6px;
    font-weight: 600;
    transition: background 0.2s;
}

.btn:hover { background: #3a56d4; }

/* ===== Card grid ===== */
.cards {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
    gap: 1.5rem;
    margin: 2rem 0;
}

.card {
    background: #fff;
    border-radius: 8px;
    padding: 1.5rem;
    box-shadow: 0 1px 3px rgba(0,0,0,0.08);
    border: 1px solid #e9ecef;
}

.card h2 {
    font-size: 1.1rem;
    margin-bottom: 0.5rem;
}

.card p {
    font-size: 0.925rem;
    color: #555;
}

/* ===== Topic list ===== */
.topic-list {
    display: flex;
    flex-direction: column;
    gap: 1rem;
    margin-top: 1.5rem;
}

.topic-card {
    display: block;
    background: #fff;
    border: 1px solid #e9ecef;
    border-radius: 8px;
    padding: 1.25rem 1.5rem;
    text-decoration: none;
    color: inherit;
    transition: box-shadow 0.2s, border-color 0.2s;
}

.topic-card:hover {
    border-color: #4361ee;
    box-shadow: 0 2px 8px rgba(67,97,238,0.12);
}

.topic-card h2 {
    font-size: 1.1rem;
    margin: 0.35rem 0 0.35rem;
}

.topic-card p {
    font-size: 0.9rem;
    color: #555;
}

/* ===== Badge ===== */
.badge {
    display: inline-block;
    font-size: 0.75rem;
    font-weight: 600;
    padding: 0.2rem 0.6rem;
    background: #eef0ff;
    color: #4361ee;
    border-radius: 4px;
    text-transform: uppercase;
    letter-spacing: 0.04em;
}

/* ===== Generic page ===== */
.page h1 {
    font-size: 2rem;
    margin-bottom: 0.75rem;
}

.page p { margin-bottom: 1rem; color: #444; }

.page ul { margin: 1rem 0 1rem 1.5rem; }
.page li { margin-bottom: 0.35rem; }

.back-link {
    display: inline-block;
    margin-bottom: 1rem;
    color: #4361ee;
    text-decoration: none;
    font-size: 0.925rem;
}

.back-link:hover { text-decoration: underline; }

/* ===== Footer ===== */
footer {
    text-align: center;
    padding: 1.5rem;
    font-size: 0.85rem;
    color: #888;
    border-top: 1px solid #e9ecef;
}