body {
    margin: 0;
    padding: 0;
    font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
    background: #f5f5f7;
    color: #222222;
}

/* top bar */

.topbar {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 14px 24px;
    border-bottom: 1px solid rgba(0, 0, 0, 0.06);
    background: #ffffff;
    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.04);
}

.brand {
    display: flex;
    align-items: center;
    gap: 10px;
}

.logoCircle {
    width: 32px;
    height: 32px;
    border-radius: 999px;
    background: radial-gradient(circle at 30% 20%, #48c78e, #1a9c5e);
    display: flex;
    justify-content: center;
    align-items: center;
    color: #ffffff;
    font-weight: 700;
    font-size: 18px;
    box-shadow: 0 6px 16px rgba(0, 0, 0, 0.18);
}

.brandName {
    font-weight: 600;
    font-size: 16px;
    letter-spacing: 0.04em;
    text-transform: uppercase;
    color: #111827;
}

.tagline {
    font-size: 12px;
    color: #6b7280;
}

.badge {
    padding: 6px 12px;
    border-radius: 999px;
    background: #ecfdf3;
    color: #15803d;
    font-size: 11px;
    letter-spacing: 0.08em;
    text-transform: uppercase;
    border: 1px solid #bbf7d0;
}

/* layout */

.content {
    max-width: 980px;
    margin: 0 auto;
    padding: 24px 16px 40px;
}

.uploadSection {
    margin-bottom: 28px;
    background: #ffffff;
    border-radius: 14px;
    padding: 18px 18px 20px;
    box-shadow: 0 10px 30px rgba(15, 23, 42, 0.06);
    border: 1px solid rgba(148, 163, 184, 0.25);
}

.uploadSection h1 {
    font-size: 22px;
    margin: 0 0 8px;
    color: #111827;
}

.introText {
    margin: 0 0 14px;
    font-size: 14px;
    color: #4b5563;
}

.uploadForm {
    display: flex;
    flex-wrap: wrap;
    gap: 10px;
    align-items: center;
    margin-top: 4px;
}

.uploadForm input[type="file"] {
    font-size: 13px;
    max-width: 260px;
    color: #111827;
}

.btnPrimary {
    background: linear-gradient(135deg, #22c55e, #16a34a);
    border: none;
    border-radius: 999px;
    padding: 8px 20px;
    font-size: 13px;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    cursor: pointer;
    color: #ffffff;
    box-shadow: 0 10px 24px rgba(22, 163, 74, 0.35);
}

.btnPrimary:hover {
    filter: brightness(1.04);
}

.errorMsg {
    margin-top: 10px;
    font-size: 13px;
    color: #b91c1c;
}

/* viewer */

.viewerSection {
    margin-top: 12px;
}

.viewerSection h2 {
    margin: 0 0 4px;
    font-size: 18px;
    color: #111827;
}

.viewerHint {
    font-size: 12px;
    color: #6b7280;
    margin-bottom: 8px;
}

.viewerArea {
    width: 100%;
    height: 380px;
    background: radial-gradient(circle at 0 0, #ffffff, #e5e7eb);
    border-radius: 16px;
    border: 1px solid rgba(148, 163, 184, 0.45);
    overflow: hidden;
    box-shadow: 0 18px 40px rgba(15, 23, 42, 0.08);
}

/* responsive */

@media (max-width: 720px) {
    .topbar {
        flex-direction: column;
        align-items: flex-start;
        gap: 8px;
    }

    .content {
        padding: 20px 12px 32px;
    }

    .uploadSection {
        padding: 16px 14px 18px;
    }

    .viewerArea {
        height: 320px;
    }
}