* { box-sizing: border-box; }

html, body {
    margin: 0;
    padding: 0;
    height: 100%;
    font-family: system-ui, -apple-system, "Segoe UI", Roboto, Arial, sans-serif;
    background: #f3f4f6;
    color: #111827;
}

.viewer-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 1rem;
    padding: 0.75rem 1.25rem;
    background: #111827;
    color: #ffffff;
    box-shadow: 0 1px 3px rgba(0,0,0,.15);
}

.viewer-header h1 {
    font-size: 1.05rem;
    font-weight: 600;
    margin: 0;
    letter-spacing: .2px;
}

.open-new {
    color: #93c5fd;
    text-decoration: none;
    font-size: .9rem;
    padding: .35rem .75rem;
    border: 1px solid #374151;
    border-radius: 6px;
    transition: background .15s ease;
}
.open-new:hover { background: #1f2937; }

.viewer-body {
    height: calc(100% - 52px);
    width: 100%;
}

.viewer-body iframe {
    width: 100%;
    height: 100%;
    border: 0;
    display: block;
    background: #ffffff;
}

@media (max-width: 600px) {
    .viewer-header { flex-direction: column; align-items: flex-start; }
    .viewer-body   { height: calc(100% - 92px); }
}