:root {
    --primary: #2563eb;
    --primary-hover: #1d4ed8;
    --bg-color: #f8fafc;
    --surface: #ffffff;
    --text-main: #0f172a;
    --text-muted: #64748b;
    --border: #e2e8f0;
    --danger: #ef4444;
    --success: #10b981;
    --radius: 12px;
}

* { box-sizing: border-box; margin: 0; padding: 0; font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif; }
body { background-color: var(--bg-color); color: var(--text-main); line-height: 1.6; }
.container { max-width: 1040px; margin: 0 auto; padding: 0 20px; }
.text-center { text-align: center; }

/* Navbar */
.navbar { background: var(--surface); border-bottom: 1px solid var(--border); padding: 16px 0; }
.nav-container { display: flex; justify-content: space-between; align-items: center; }
.brand-logo { display: flex; align-items: center; gap: 8px; font-weight: 700; font-size: 1.25rem; color: var(--primary); text-decoration: none; }
.nav-links a { color: var(--text-muted); text-decoration: none; margin-left: 20px; font-size: 0.95rem; }
.nav-links a:hover { color: var(--primary); }

/* Hero */
.hero-section { padding: 48px 0 32px; }
.hero-section h1 { font-size: 2.25rem; margin-bottom: 12px; letter-spacing: -0.02em; }
.hero-subtitle { color: var(--text-muted); font-size: 1.1rem; }

/* Upload Drop Zone */
.converter-wrapper { margin-bottom: 60px; }
.drop-zone {
    background: var(--surface);
    border: 2px dashed #cbd5e1;
    border-radius: var(--radius);
    padding: 40px 20px;
    text-align: center;
    cursor: pointer;
    transition: all 0.2s ease;
}
.drop-zone.dragover { border-color: var(--primary); background-color: #eff6ff; }
.upload-icon { width: 48px; height: 48px; stroke: var(--primary); margin-bottom: 12px; }
.browse-btn { color: var(--primary); text-decoration: underline; }
.drop-note { font-size: 0.85rem; color: var(--text-muted); margin-top: 6px; }

/* Actions Bar */
.batch-actions {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin: 20px 0 16px;
    background: var(--surface);
    padding: 12px 20px;
    border-radius: var(--radius);
    border: 1px solid var(--border);
}
.hidden { display: none !important; }
.batch-stats { font-size: 0.9rem; font-weight: 500; color: var(--text-muted); display: flex; gap: 16px; }
.btn { padding: 8px 16px; border-radius: 6px; border: none; cursor: pointer; font-weight: 600; font-size: 0.9rem; }
.btn:disabled { opacity: 0.5; cursor: not-allowed; }
.btn-primary { background: var(--primary); color: #fff; }
.btn-primary:not(:disabled):hover { background: var(--primary-hover); }
.btn-outline { background: transparent; border: 1px solid var(--border); color: var(--text-muted); }
.btn-outline:hover { background: #f1f5f9; }

/* File Grid */
.file-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(230px, 1fr)); gap: 16px; }
.file-card {
    position: relative;
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    padding: 12px;
    display: flex;
    flex-direction: column;
}
.remove-btn {
    position: absolute;
    top: 6px;
    right: 6px;
    width: 24px;
    height: 24px;
    background: rgba(15, 23, 42, 0.6);
    color: #fff;
    border: none;
    border-radius: 50%;
    cursor: pointer;
    font-size: 12px;
    z-index: 2;
}
.remove-btn:hover { background: var(--danger); }
.card-thumb { width: 100%; height: 140px; object-fit: contain; background: #f1f5f9; border-radius: 8px; margin-bottom: 10px; }
.card-info { font-size: 0.85rem; margin-bottom: 8px; }
.card-filename { white-space: nowrap; overflow: hidden; text-overflow: ellipsis; font-weight: 500; }
.card-status { color: var(--text-muted); font-size: 0.75rem; }

/* Progress Bar */
.progress-bar-bg { width: 100%; height: 6px; background: #e2e8f0; border-radius: 3px; overflow: hidden; margin-top: auto; }
.progress-bar-fill { height: 100%; width: 0%; background: var(--primary); transition: width 0.3s; }
.file-card.success .progress-bar-fill { background: var(--success); }
.file-card.error .progress-bar-fill { background: var(--danger); }

.download-single-btn {
    margin-top: 10px;
    padding: 6px 0;
    text-align: center;
    background: #eff6ff;
    color: var(--primary);
    text-decoration: none;
    border-radius: 6px;
    font-size: 0.8rem;
    font-weight: 600;
}
.download-single-btn:hover { background: #dbeafe; }

/* SEO Content */
.content-section { padding: 40px 0; border-top: 1px solid var(--border); }
.content-section h2 { font-size: 1.7rem; margin-bottom: 16px; }
.content-section p { color: #334155; margin-bottom: 16px; }
.steps-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(260px, 1fr)); gap: 20px; margin-top: 24px; }
.step-card { background: var(--surface); padding: 24px; border-radius: var(--radius); border: 1px solid var(--border); }
.step-num { font-size: 1.5rem; font-weight: 800; color: var(--primary); margin-bottom: 8px; }
.comparison-table { width: 100%; border-collapse: collapse; margin-top: 16px; background: var(--surface); border: 1px solid var(--border); }
.comparison-table th, .comparison-table td { padding: 12px 16px; text-align: left; border-bottom: 1px solid var(--border); font-size: 0.9rem; }
.comparison-table th { background: #f8fafc; }
.faq-item { margin-bottom: 20px; background: var(--surface); padding: 20px; border-radius: var(--radius); border: 1px solid var(--border); }
.faq-item h3 { font-size: 1.1rem; margin-bottom: 8px; }
.footer { padding: 30px 0; border-top: 1px solid var(--border); color: var(--text-muted); font-size: 0.85rem; }