diff --git a/site/src/components/Explore.svelte b/site/src/components/Explore.svelte
index b51b13c..dfd684e 100644
--- a/site/src/components/Explore.svelte
+++ b/site/src/components/Explore.svelte
@@ -30,13 +30,14 @@
 
   // Tile layers — same as planner
   const TILES: Record<string, { tiles: string[]; attribution: string; label: string }> = {
-    cyclosm:   { label: 'Cycle',     attribution: '© CyclOSM | © OpenStreetMap contributors', tiles: ['https://a.tile-cyclosm.openstreetmap.fr/cyclosm/{z}/{x}/{y}.png','https://b.tile-cyclosm.openstreetmap.fr/cyclosm/{z}/{x}/{y}.png','https://c.tile-cyclosm.openstreetmap.fr/cyclosm/{z}/{x}/{y}.png'] },
+    grey:      { label: 'Grey',      attribution: '© CARTO | © OpenStreetMap contributors',     tiles: ['https://a.basemaps.cartocdn.com/light_all/{z}/{x}/{y}.png','https://b.basemaps.cartocdn.com/light_all/{z}/{x}/{y}.png','https://c.basemaps.cartocdn.com/light_all/{z}/{x}/{y}.png'] },
+    cyclosm:   { label: 'Cycle',     attribution: '© CyclOSM | © OpenStreetMap contributors',   tiles: ['https://a.tile-cyclosm.openstreetmap.fr/cyclosm/{z}/{x}/{y}.png','https://b.tile-cyclosm.openstreetmap.fr/cyclosm/{z}/{x}/{y}.png','https://c.tile-cyclosm.openstreetmap.fr/cyclosm/{z}/{x}/{y}.png'] },
     osm:       { label: 'OSM',       attribution: '© OpenStreetMap contributors',               tiles: ['https://tile.openstreetmap.org/{z}/{x}/{y}.png'] },
     topo:      { label: 'Topo',      attribution: '© OpenTopoMap | © OpenStreetMap contributors', tiles: ['https://a.tile.opentopomap.org/{z}/{x}/{y}.png','https://b.tile.opentopomap.org/{z}/{x}/{y}.png','https://c.tile.opentopomap.org/{z}/{x}/{y}.png'] },
     satellite: { label: 'Sat',       attribution: '© Esri World Imagery',                       tiles: ['https://server.arcgisonline.com/ArcGIS/rest/services/World_Imagery/MapServer/tile/{z}/{y}/{x}'] },
   };
-  const TILE_ORDER = ['cyclosm', 'osm', 'topo', 'satellite'];
-  let tileKey = 'cyclosm';
+  const TILE_ORDER = ['grey', 'cyclosm', 'osm', 'topo', 'satellite'];
+  let tileKey = 'grey';
 
   const TYPE_COLORS: Record<string, string> = {
     cycling: '#e879a0',
@@ -56,7 +57,8 @@
   $: allTypes = [...new Set(tracks.map(t => t.type))].sort();
   $: availableYears = [...new Set(tracks.map(t => t.date.slice(0,4)).filter(Boolean))].sort().reverse();
 
-  $: if (allTypes.length > 0 && selectedTypes.size === 0) selectedTypes = new Set(allTypes);
+  let typesInitialized = false;
+  $: if (allTypes.length > 0 && !typesInitialized) { selectedTypes = new Set(allTypes); typesInitialized = true; }
 
   $: filteredTracks = tracks.filter(t => {
     if (!selectedTypes.has(t.type)) return false;
@@ -170,7 +172,7 @@
     map = new maplibregl.Map({
       container: mapEl,
       style: { version: 8,
-        sources: { base: { type: 'raster', tiles: TILES.cyclosm.tiles, tileSize: 256, attribution: TILES.cyclosm.attribution } },
+        sources: { base: { type: 'raster', tiles: TILES.grey.tiles, tileSize: 256, attribution: TILES.grey.attribution } },
         layers: [{ id: 'base', type: 'raster', source: 'base' }],
       },
       center: [12, 42], zoom: 5,
@@ -190,16 +192,19 @@
         },
       });
 
+      const heatWidth   = ['interpolate', ['linear'], ['zoom'],  5, 2,    10, 4,    14, 7,    18, 10];
+      const heatOpacity = ['interpolate', ['linear'], ['zoom'],  5, 0.10, 10, 0.12, 14, 0.15, 18, 0.18];
+
       // Global heatmap — all lines in warm amber, very low opacity so overlapping routes stack up
       map.addLayer({ id: 'explore-heat-global', type: 'line', source: 'explore-lines', layout: { visibility: 'none' },
-        paint: { 'line-width': 4, 'line-opacity': 0.10, 'line-blur': 1, 'line-color': '#f97316' },
+        paint: { 'line-width': heatWidth, 'line-opacity': heatOpacity, 'line-blur': 1, 'line-color': '#f97316' },
       });
 
       // Per-type heatmap layers — same accumulation trick, type-specific colour
       for (const [type, hex] of Object.entries(TYPE_COLORS)) {
         map.addLayer({ id: `explore-heat-${type}`, type: 'line', source: 'explore-lines',
           filter: ['==', ['get', 'type'], type], layout: { visibility: 'none' },
-          paint: { 'line-width': 4, 'line-opacity': 0.12, 'line-blur': 1, 'line-color': hex },
+          paint: { 'line-width': heatWidth, 'line-opacity': heatOpacity, 'line-blur': 1, 'line-color': hex },
         });
       }