diff --git a/.gitignore b/.gitignore
index 4ba6711..eb17b4a 100644
--- a/.gitignore
+++ b/.gitignore
@@ -199,3 +199,9 @@ zhihu-articles/
 
 # Results directory (test outputs, charts, etc.)
 results/
+
+# Node.js (local testing only)
+node_modules/
+package.json
+package-lock.json
+rotation/test_screenshot.mjs
diff --git a/rotation/backtest_viewer.html b/rotation/backtest_viewer.html
index a7a77e3..6a9bd88 100644
--- a/rotation/backtest_viewer.html
+++ b/rotation/backtest_viewer.html
@@ -152,11 +152,15 @@ tr.below-threshold { color: #484f58; }
 </div>
 
 <script>
-let DATA = null;
-let currentIdx = 0;
-let playing = false;
-let playTimer = null;
-let rebalanceDays = [];
+// Use window. to allow external access (for Playwright screenshot injection)
+window.DATA = null;
+window.currentIdx = 0;
+window.playing = false;
+window.playTimer = null;
+window.rebalanceDays = [];
+
+// Convenience aliases for script-internal use
+const DATA_PROXY = { get data() { return window.DATA; }, set data(v) { window.DATA = v; } };
 
 const $ = id => document.getElementById(id);
 
diff --git a/rotation/html_report.py b/rotation/html_report.py
new file mode 100644
index 0000000..3992e08
--- /dev/null
+++ b/rotation/html_report.py
@@ -0,0 +1,285 @@
+"""
+HTML Report Screenshot Generator
+
+Uses Playwright to render backtest_viewer.html in headless Chromium
+and capture a full-page screenshot as PNG.
+
+Intended to be called after export_results() has produced simple_rotation_detail.json.
+"""
+
+import json
+from pathlib import Path
+from typing import Optional, List, Dict
+import numpy as np
+
+
+def compute_monthly_returns(daily_records: List[Dict]) -> List[Dict]:
+    """Compute monthly cumulative returns from daily_records.
+
+    Returns list of {year, month, return_pct, trading_days} dicts.
+    """
+    if not daily_records:
+        return []
+
+    # Group by (year, month)
+    monthly: Dict[str, List[float]] = {}
+    for rec in daily_records:
+        date_str = rec['date']
+        ym = date_str[:7]  # "2024-01"
+        if ym not in monthly:
+            monthly[ym] = []
+        monthly[ym].append(rec['nav'])
+
+    results = []
+    for ym in sorted(monthly.keys()):
+        navs = monthly[ym]
+        if len(navs) < 1:
+            continue
+        # Monthly return = last_nav / prev_last_nav - 1
+        # prev_last_nav = last nav of previous month, or first nav of this month's start
+        # More accurate: use the nav just before the first day of this month
+        results.append({
+            'year_month': ym,
+            'start_nav': navs[0],
+            'end_nav': navs[-1],
+            'trading_days': len(navs),
+        })
+
+    # Compute returns sequentially
+    for i, r in enumerate(results):
+        if i == 0:
+            # First month: return relative to first NAV (which is usually ~1.0)
+            # Use previous day's nav if available, otherwise start_nav itself
+            r['return_pct'] = 0.0  # first month baseline
+        else:
+            r['return_pct'] = r['start_nav'] / results[i-1]['end_nav'] - 1
+        r['month_return'] = r['end_nav'] / r['start_nav'] - 1
+
+    return results
+
+
+def generate_html_screenshot(
+    detail_json_path: str,
+    output_path: str,
+    target_date: Optional[str] = None,
+    viewport_width: int = 1920,
+    viewport_height: int = 1080,
+    show_monthly_table: bool = True,
+    daily_records: Optional[List[Dict]] = None,
+):
+    """Render backtest_viewer.html and capture screenshot.
+
+    Args:
+        detail_json_path: Path to simple_rotation_detail.json
+        output_path: Output PNG path
+        target_date: Date string to navigate to (YYYY-MM-DD). None = last day.
+        viewport_width: Browser viewport width
+        viewport_height: Browser viewport height (minimum, will expand for full page)
+        show_monthly_table: Whether to inject monthly returns table
+        daily_records: List of daily record dicts (needed for monthly table)
+    """
+    try:
+        from playwright.sync_api import sync_playwright
+    except ImportError:
+        print("  x Playwright not installed. Run: pip install playwright && playwright install chromium")
+        return
+
+    detail_path = Path(detail_json_path)
+    if not detail_path.exists():
+        print(f"  x Detail JSON not found: {detail_json_path}")
+        return
+
+    output = Path(output_path)
+    output.parent.mkdir(parents=True, exist_ok=True)
+
+    html_path = Path(__file__).parent / 'backtest_viewer.html'
+    if not html_path.exists():
+        print(f"  x backtest_viewer.html not found: {html_path}")
+        return
+
+    with open(detail_path, 'r', encoding='utf-8') as f:
+        detail_data = json.load(f)
+
+    print(f"  Launching headless Chromium...")
+
+    with sync_playwright() as p:
+        browser = p.chromium.launch(headless=True)
+        page = browser.new_page(viewport={'width': viewport_width, 'height': viewport_height})
+
+        # Load the HTML file
+        page.goto(f'file://{html_path.absolute()}')
+        page.wait_for_selector('#loader')
+
+        # Inject data directly (skip file input)
+        page.evaluate(f"""
+            (data) => {{
+                DATA = data;
+                document.getElementById('loader').style.display = 'none';
+                document.getElementById('app').classList.add('active');
+
+                // Build rebalance day index
+                rebalanceDays = [];
+                DATA.days.forEach((d, i) => {{ if (d.is_rebalance) rebalanceDays.push(i); }});
+
+                // Set date picker range
+                document.getElementById('date-picker').min = DATA.days[0].date;
+                document.getElementById('date-picker').max = DATA.days[DATA.days.length - 1].date;
+            }}
+        """, detail_data)
+
+        # Navigate to target date
+        if target_date:
+            page.evaluate(f"""
+                (targetDate) => {{
+                    const idx = DATA.days.findIndex(d => d.date === targetDate);
+                    if (idx >= 0) {{
+                        currentIdx = idx;
+                        render(currentIdx);
+                        drawChart();
+                        drawChartMarker();
+                    }}
+                }}
+            """, target_date)
+        else:
+            # Navigate to last day
+            page.evaluate("""
+                () => {
+                    currentIdx = DATA.days.length - 1;
+                    render(currentIdx);
+                    drawChart();
+                    drawChartMarker();
+                }
+            """)
+
+        # Wait for rendering
+        page.wait_for_timeout(500)
+
+        # Inject monthly returns table if requested
+        if show_monthly_table and daily_records:
+            monthly = compute_monthly_returns(daily_records)
+            if monthly:
+                _inject_monthly_table(page, monthly)
+                page.wait_for_timeout(300)
+
+        # Take full page screenshot
+        page.screenshot(path=str(output), full_page=True)
+        browser.close()
+
+    print(f"  + HTML Report Screenshot: {output}")
+
+
+def _inject_monthly_table(page, monthly_data: List[Dict]):
+    """Inject monthly returns table into the page."""
+
+    # Build HTML for monthly table
+    rows_html = ""
+    for r in monthly_data:
+        ret = r['month_return']
+        cls = 'positive' if ret >= 0 else 'negative'
+        rows_html += f"""
+        <tr>
+            <td>{r['year_month']}</td>
+            <td style="color:{'#3fb950' if ret >= 0 else '#da3633'};font-weight:600">
+                {(ret * 100):+.2f}%
+            </td>
+            <td>{r['end_nav']:.4f}</td>
+            <td>{r['trading_days']}</td>
+        </tr>
+        """
+
+    # Also compute yearly returns
+    yearly: Dict[str, float] = {}
+    yearly_navs: Dict[str, float] = {}  # last nav of each year
+    for r in monthly_data:
+        year = r['year_month'][:4]
+        yearly[year] = r['end_nav']
+    yearly_list = sorted(yearly.keys())
+    yearly_rows = ""
+    for i, year in enumerate(yearly_list):
+        if i == 0:
+            yr_ret = 0.0
+        else:
+            prev_year = yearly_list[i-1]
+            yr_ret = yearly[year] / yearly[prev_year] - 1
+        cls_color = '#3fb950' if yr_ret >= 0 else '#da3633'
+        yearly_rows += f"""
+        <tr>
+            <td>{year}</td>
+            <td style="color:{cls_color};font-weight:600">{(yr_ret * 100):+.2f}%</td>
+            <td>{yearly[year]:.4f}</td>
+        </tr>
+        """
+
+    html = f"""
+    <div id="monthly-panel" style="
+        padding: 16px;
+        background: #161b22;
+        border-top: 1px solid #30363d;
+    ">
+        <div style="display: flex; gap: 32px; align-items: flex-start;">
+            <div style="flex: 1;">
+                <h3 style="color:#8b949e;font-size:11px;text-transform:uppercase;letter-spacing:1px;margin-bottom:8px;">
+                    月度累计收益
+                </h3>
+                <table style="width:100%;border-collapse:collapse;font-size:12px;font-family:monospace;">
+                    <thead>
+                        <tr style="background:#0d1117;">
+                            <th style="text-align:left;padding:6px 8px;color:#8b949e;border-bottom:1px solid #30363d;">月份</th>
+                            <th style="text-align:right;padding:6px 8px;color:#8b949e;border-bottom:1px solid #30363d;">月收益</th>
+                            <th style="text-align:right;padding:6px 8px;color:#8b949e;border-bottom:1px solid #30363d;">月末净值</th>
+                            <th style="text-align:right;padding:6px 8px;color:#8b949e;border-bottom:1px solid #30363d;">交易天数</th>
+                        </tr>
+                    </thead>
+                    <tbody>
+                        {rows_html}
+                    </tbody>
+                </table>
+            </div>
+            <div style="min-width: 240px;">
+                <h3 style="color:#8b949e;font-size:11px;text-transform:uppercase;letter-spacing:1px;margin-bottom:8px;">
+                    年度收益
+                </h3>
+                <table style="width:100%;border-collapse:collapse;font-size:12px;font-family:monospace;">
+                    <thead>
+                        <tr style="background:#0d1117;">
+                            <th style="text-align:left;padding:6px 8px;color:#8b949e;border-bottom:1px solid #30363d;">年度</th>
+                            <th style="text-align:right;padding:6px 8px;color:#8b949e;border-bottom:1px solid #30363d;">年收益</th>
+                            <th style="text-align:right;padding:6px 8px;color:#8b949e;border-bottom:1px solid #30363d;">年末净值</th>
+                        </tr>
+                    </thead>
+                    <tbody>
+                        {yearly_rows}
+                    </tbody>
+                </table>
+            </div>
+        </div>
+    </div>
+    """
+
+    # Append to app container
+    page.evaluate(f"""
+        (htmlContent) => {{
+            const app = document.getElementById('app');
+            const div = document.createElement('div');
+            div.innerHTML = htmlContent;
+            app.appendChild(div);
+        }}
+    """, html)
+
+    # Apply row borders
+    page.evaluate("""
+        () => {
+            document.querySelectorAll('#monthly-panel td').forEach(td => {
+                td.style.borderBottom = '1px solid #21262d';
+                td.style.padding = '5px 8px';
+            });
+        }
+    """)
+
+
+if __name__ == "__main__":
+    # Test: run with existing detail JSON
+    import sys
+    detail = sys.argv[1] if len(sys.argv) > 1 else "rotation/results/simple_rotation_detail.json"
+    output = sys.argv[2] if len(sys.argv) > 2 else "rotation/results/simple_rotation_html_report.png"
+    generate_html_screenshot(detail, output)
diff --git a/rotation/simple_rotation.py b/rotation/simple_rotation.py
index 81d500d..39c723b 100644
--- a/rotation/simple_rotation.py
+++ b/rotation/simple_rotation.py
@@ -1418,6 +1418,37 @@ class SimpleRotationStrategy:
         plt.close()
         print(f"  + Report: {chart_path}")
 
+    def generate_html_report(self, output_dir: str = None, target_date: str = None):
+        """Generate HTML-based report screenshot using Playwright.
+
+        Renders backtest_viewer.html in headless Chromium and captures
+        the ranking table + monthly returns as a PNG.
+
+        Args:
+            output_dir: Directory to save the PNG (default: rotation/results)
+            target_date: Date to navigate to (YYYY-MM-DD). None = last day.
+        """
+        from rotation.html_report import generate_html_screenshot
+
+        if output_dir is None:
+            output_dir = Path(__file__).parent / 'results'
+        output_dir = Path(output_dir)
+        output_dir.mkdir(parents=True, exist_ok=True)
+
+        detail_path = output_dir / 'simple_rotation_detail.json'
+        if not detail_path.exists():
+            print(f"  x Detail JSON not found: {detail_path}")
+            print("    Run export_results() first.")
+            return
+
+        output_path = output_dir / 'simple_rotation_html_report.png'
+        generate_html_screenshot(
+            detail_json_path=str(detail_path),
+            output_path=str(output_path),
+            target_date=target_date,
+            daily_records=self.daily_records,
+        )
+
 
 # ============================================================
 # Entry point
@@ -1433,3 +1464,4 @@ if __name__ == "__main__":
     if result:
         strategy.export_results()
         strategy.generate_report()
+        strategy.generate_html_report()