:root {
    font-family: "Inter", "Segoe UI", system-ui, -apple-system, BlinkMacSystemFont, sans-serif;
    --bg: #f6f7fb;
    --sidebar: #ffffff;
    --preview: #ffffff;
    --border: #e0e6f0;
    --text: #1e293b;
    --muted: #64748b;
    --primary: #2563eb;
    --primary-dark: #1d4ed8;
}

* {
    box-sizing: border-box;
}

body {
    margin: 0;
    background: var(--bg);
    color: var(--text);
}

.topbar {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 1.5rem 2rem;
    border-bottom: 1px solid var(--border);
    background: #fff;
    flex-wrap: wrap;
    gap: 1rem;
}

.topbar h1 {
    margin: 0;
    font-size: clamp(1.6rem, 4vw, 2.2rem);
}

.eyebrow {
    text-transform: uppercase;
    letter-spacing: 0.1em;
    font-size: 0.75rem;
    color: var(--primary);
    margin: 0 0 0.25rem;
}

.cta {
    padding: 0.75rem 1.5rem;
    border-radius: 999px;
    border: none;
    background: var(--primary);
    color: #fff;
    text-decoration: none;
    font-weight: 600;
    box-shadow: 0 10px 24px rgba(37, 99, 235, 0.2);
}

.cta:hover {
    background: var(--primary-dark);
}

.layout {
    display: grid;
    grid-template-columns: 320px 1fr;
    min-height: calc(100vh - 96px);
}

.sidebar {
    background: var(--sidebar);
    border-right: 1px solid var(--border);
    padding: 1.5rem;
}

.sidebar h2 {
    margin-top: 0;
    font-size: 1.15rem;
}

.sidebar ul {
    list-style: none;
    padding: 0;
    margin: 1rem 0 0;
    display: flex;
    flex-direction: column;
    gap: 0.35rem;
}

.sidebar button {
    width: 100%;
    padding: 0.75rem 1rem;
    border-radius: 0.75rem;
    border: 1px solid transparent;
    background: transparent;
    text-align: left;
    font-size: 0.95rem;
    color: var(--muted);
    cursor: pointer;
    transition: border 120ms ease, background 120ms ease, color 120ms ease;
}

.sidebar button:hover {
    border-color: var(--border);
    background: #f8fafc;
    color: var(--text);
}

.sidebar button.active {
    border-color: rgba(37, 99, 235, 0.4);
    background: rgba(37, 99, 235, 0.08);
    color: var(--primary);
    font-weight: 600;
}

.preview {
    padding: 1.5rem 2rem;
    display: flex;
    flex-direction: column;
    gap: 1rem;
}

.preview__header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    flex-wrap: wrap;
    gap: 0.5rem;
}

.preview__header h2 {
    margin: 0;
}

.open-link {
    text-decoration: none;
    font-weight: 600;
    color: var(--primary);
}

iframe {
    flex: 1;
    width: 100%;
    border: 1px solid var(--border);
    border-radius: 1rem;
    background: var(--preview);
    min-height: 520px;
}

@media (max-width: 960px) {
    .layout {
        grid-template-columns: 1fr;
    }

    .sidebar {
        border-right: none;
        border-bottom: 1px solid var(--border);
    }
}