.topbar {
    position: sticky;
    top: 0;
    z-index: 20;
    display: flex;
    flex-wrap: wrap;
    align-items: center;
    gap: 0.75rem 1.25rem;
    padding: 0.7rem clamp(1rem, 4vw, 2.5rem);
    border-bottom: 1px solid var(--border);
    background: rgba(255, 255, 255, 0.92);
    backdrop-filter: blur(8px);
}

.brand {
    color: var(--text);
    font-size: 1.05rem;
    font-weight: 800;
    letter-spacing: -0.02em;
}

.brand span,
.login-card__brand span {
    color: var(--accent);
}

.brand:hover {
    text-decoration: none;
}

.nav {
    display: flex;
    flex: 1;
    flex-wrap: wrap;
    gap: 0.25rem;
    justify-content: center;
}

.nav a {
    padding: 0.35rem 0.7rem;
    border-radius: 999px;
    color: var(--muted);
    font-weight: 600;
    font-size: 0.92rem;
}

.nav a:hover {
    background: var(--surface-soft);
    color: var(--text);
    text-decoration: none;
}

.nav a.is-active {
    background: var(--surface-soft);
    color: var(--accent);
}

.logout {
    margin: 0;
}

.page {
    width: min(1080px, 100%);
    margin: 0 auto;
    padding: clamp(1.2rem, 3vw, 2.2rem) clamp(1rem, 4vw, 2rem) 4rem;
}

.page--narrow {
    width: min(820px, 100%);
}

.page-head {
    display: flex;
    flex-wrap: wrap;
    align-items: flex-start;
    justify-content: space-between;
    gap: 1rem;
    margin-bottom: 1.2rem;
}

.hero {
    padding: clamp(1.2rem, 3vw, 2rem) 0 1.6rem;
}

.hero h1 {
    max-width: 24ch;
    margin-bottom: 0.7rem;
    font-size: clamp(1.7rem, 4vw, 2.6rem);
    letter-spacing: -0.03em;
}

.hero p {
    max-width: 52ch;
}

.hero__actions {
    display: flex;
    flex-wrap: wrap;
    gap: 0.6rem;
    margin-top: 1rem;
}

.stat-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(140px, 1fr));
    gap: 0.8rem;
    margin-bottom: 1.6rem;
}

.toolbar {
    display: flex;
    flex-wrap: wrap;
    align-items: center;
    gap: 0.5rem;
    margin-bottom: 1.1rem;
}

.topic-lists {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
    gap: 1rem;
    margin-top: 1rem;
}

/* Login */

.login-page {
    display: grid;
    place-items: center;
    padding: 1.5rem;
}

.login-card {
    width: min(420px, 100%);
    padding: clamp(1.4rem, 4vw, 2.2rem);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    background: var(--surface);
    box-shadow: var(--shadow);
}

.login-card__brand {
    margin-bottom: 0.4rem;
    font-size: 1.4rem;
    font-weight: 800;
    letter-spacing: -0.03em;
}

.login-card__hint {
    margin: 1rem 0 0;
    font-size: 0.84rem;
}

@media (max-width: 620px) {
    .topbar {
        padding: 0.6rem 1rem;
    }

    .nav {
        order: 3;
        flex-basis: 100%;
        justify-content: flex-start;
        overflow-x: auto;
        flex-wrap: nowrap;
    }

    .nav a {
        white-space: nowrap;
    }

    .logout {
        margin-left: auto;
    }

    .page {
        padding-bottom: 3rem;
    }
}