Your first MapLibre map

• Give #map a real height, because a zero-height parent yields a blank page with no error.
• Pass style at construction, for example the token-free demotiles style, since v4 rejects a missing style.
• Add sources and layers inside map.on('load') and re-add them after any setStyle call.

<!DOCTYPE html>
<html lang="zh-CN">
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/maplibre-gl@4/dist/maplibre-gl.css">
  <style>
    html, body { height: 100%; margin: 0; }
    #map { height: 100%; }
  </style>
</head>
<body>
  <div id="map"></div>
  <script src="https://cdn.jsdelivr.net/npm/maplibre-gl@4/dist/maplibre-gl.js"></script>
  <script>
    var map = new maplibregl.Map({
      container: 'map',
      style: 'https://demotiles.maplibre.org/style.json',
      center: [116.391263, 39.907359],
      zoom: 4
    });

    map.addControl(new maplibregl.NavigationControl(), 'top-right');
  </script>
</body>
</html>

map.on('load', function () {
  map.addSource('points', {
    type: 'geojson',
    data: { type: 'Point', coordinates: [116.39, 39.90] }
  });

  map.addLayer({
    id: 'points',
    type: 'circle',
    source: 'points',
    paint: { 'circle-radius': 6, 'circle-color': '#1f5fd0' }
  });
});

• Using Mapbox style URLs with access tokens returns 401 and only shows failed tile requests.
• Zooming past level 6 on demotiles overzooms stretched tiles, which looks like a rendering bug.