:root {
    --bg: #f4f6f8;
    --card: #ffffff;
    --text: #1f2937;
    --muted: #6b7280;
    --primary: #0b4ea2;
    --secondary: #146c43;
    --border: #d8dee6;
}

* {
    box-sizing: border-box;
}

body {
    margin: 0;
    font-family: "Segoe UI", Tahoma, Geneva, Verdana, sans-serif;
    background: linear-gradient(180deg, #eef3f8 0%, #f8fafc 100%);
    color: var(--text);
}

.viewer-shell {
    max-width: 1100px;
    margin: 0 auto;
    padding: 1rem;
}

.viewer-card {
    background: var(--card);
    border: 1px solid var(--border);
    border-radius: 12px;
    box-shadow: 0 8px 20px rgba(15, 23, 42, 0.06);
    overflow: hidden;
}

.viewer-header {
    padding: 1.2rem;
    border-bottom: 1px solid var(--border);
    background: linear-gradient(90deg, #ffffff 0%, #f7fafc 100%);
}

.viewer-title {
    margin: 0;
    font-size: 1.35rem;
    line-height: 1.3;
}

.viewer-subtitle {
    margin: 0.45rem 0 0 0;
    color: var(--muted);
    font-size: 0.95rem;
}

.viewer-actions {
    padding: 1rem 1.2rem;
    display: flex;
    flex-wrap: wrap;
    gap: 0.6rem;
    border-bottom: 1px solid var(--border);
}

.viewer-btn {
    display: inline-block;
    border: 0;
    border-radius: 8px;
    padding: 0.62rem 0.95rem;
    text-decoration: none;
    color: #fff;
    background: var(--primary);
    font-weight: 600;
    font-size: 0.92rem;
}

.viewer-btn-secondary {
    background: var(--secondary);
}

.viewer-btn-muted {
    background: #475569;
}

.viewer-frame-wrap {
    background: #fff;
}

.viewer-frame {
    width: 100%;
    min-height: 82vh;
    border: 0;
    display: block;
    background: #fff;
}

@media (max-width: 700px) {
    .viewer-title {
        font-size: 1.1rem;
    }

    .viewer-subtitle {
        font-size: 0.88rem;
    }

    .viewer-actions {
        padding: 0.85rem;
    }

    .viewer-btn {
        width: 100%;
        text-align: center;
    }

    .viewer-frame {
        min-height: 76vh;
    }
}