diff --git a/script.js b/script.js
index 1afa77c..c5844d0 100644
--- a/script.js
+++ b/script.js
@@ -1429,15 +1429,24 @@
     async function imageUrlToDataUrl(src) {
       if (!src || src.startsWith('data:')) return src;
       if (DATA_URL_CACHE.has(src)) return DATA_URL_CACHE.get(src);
+      const abs = (() => { try { return new URL(src, window.location.href).href; } catch { return src; } })();
+      const urlObj = (() => { try { return new URL(abs); } catch { return null; } })();
+      const isFile = urlObj?.protocol === 'file:';
+      if (isFile) { // file:// cannot be safely read for data URLs in-browser
+        DATA_URL_CACHE.set(src, null);
+        return null;
+      }
+
       const cachedImg = IMG_CACHE.get(src);
       const cachedUrl = imageToDataUrl(cachedImg);
       if (cachedUrl) {
         DATA_URL_CACHE.set(src, cachedUrl);
         return cachedUrl;
       }
-      const abs = (() => { try { return new URL(src, window.location.href).href; } catch { return src; } })();
+
       let dataUrl = null;
       try {
+        if (isFile) throw new Error('Skip fetch for file://');
         const resp = await fetch(abs);
         if (!resp.ok) throw new Error(`Status ${resp.status}`);
         dataUrl = await blobToDataUrl(await resp.blob());
@@ -1446,7 +1455,7 @@
         // Fallback: draw to a canvas to capture even when fetch is blocked (e.g., file://)
         dataUrl = await new Promise(resolve => {
           const img = new Image();
-          img.crossOrigin = 'anonymous';
+          if (!isFile) img.crossOrigin = 'anonymous';
           img.onload = () => {
             try {
               const c = document.createElement('canvas');
@@ -1491,7 +1500,7 @@
       await Promise.all(uniqueImageUrls.map(async (url) => dataUrlMap.set(url, await imageUrlToDataUrl(url))));
 
       const bounds = balloonsBounds();
-      const pad = 20;
+      const pad = 50; // extra room to avoid clipping drop-shadows
       const width = bounds.w + pad * 2;
       const height = bounds.h + pad * 2;
       const vb = [bounds.minX - pad, bounds.minY - pad, width, height].join(' ');
@@ -1499,12 +1508,33 @@
       let defs = '';
       let elements = '';
       const patterns = new Map();
+      const shadowFilters = new Map();
+
+      const ensureShadowFilter = (dx, dy, blurPx, alpha) => {
+        const key = `${dx}|${dy}|${blurPx}|${alpha}`;
+        if (!shadowFilters.has(key)) {
+          const id = `shadow-${shadowFilters.size}`;
+          const stdDev = Math.max(0.01, blurPx * 0.5);
+          const clampedAlpha = clamp01(alpha);
+          const flood = `<feFlood flood-color="#000000" flood-opacity="${clampedAlpha}" />`;
+          const blur = `<feGaussianBlur in="SourceAlpha" stdDeviation="${stdDev}" result="blur" />`;
+          const offset = `<feOffset dx="${dx}" dy="${dy}" in="blur" result="shadow" />`;
+          const composite = `<feComposite in="shadow" in2="SourceAlpha" operator="in" result="shadow" />`;
+          const merge = `<feMerge><feMergeNode in="shadow" /><feMergeNode in="SourceGraphic" /></feMerge>`;
+          defs += `<filter id="${id}" x="-50%" y="-50%" width="200%" height="200%" filterUnits="userSpaceOnUse" color-interpolation-filters="sRGB">${flood}${blur}${offset}${composite}${merge}</filter>`;
+          shadowFilters.set(key, id);
+        }
+        return shadowFilters.get(key);
+      };
+      const shineShadowId = ensureShadowFilter(0, 0, 3, 0.1);
 
       balloons.forEach(b => {
+        const meta = FLAT_COLORS[b.colorIdx] || {};
         let fill = b.color;
         if (b.image) {
           const patternKey = `${b.colorIdx}|${b.image}`;
-          if (!patterns.has(patternKey)) {
+          const imageHref = dataUrlMap.get(b.image);
+          if (!patterns.has(patternKey) && imageHref) {
             const patternId = `p${patterns.size}`;
             patterns.set(patternKey, patternId);
             const meta = FLAT_COLORS[b.colorIdx] || {};
@@ -1514,15 +1544,29 @@
             const imgW = zoom, imgH = zoom;
             const imgX = 0.5 - (fx * zoom);
             const imgY = 0.5 - (fy * zoom);
-            const imageHref = dataUrlMap.get(b.image) || b.image;
             defs += `<pattern id="${patternId}" patternContentUnits="objectBoundingBox" width="1" height="1">
               <image href="${imageHref}" x="${imgX}" y="${imgY}" width="${imgW}" height="${imgH}" preserveAspectRatio="xMidYMid slice" />
             </pattern>`;
           }
-          fill = `url(#${patterns.get(patternKey)})`;
+          if (patterns.has(patternKey)) fill = `url(#${patterns.get(patternKey)})`;
+        }
+        let filterAttr = '';
+        if (b.image) {
+          const lum = luminance(meta.hex || b.color);
+          if (lum > 0.6) {
+            const strength = clamp01((lum - 0.6) / 0.4);
+            const blur = 4 + 4 * strength;
+            const offsetY = 1 + 2 * strength;
+            const alpha = 0.05 + 0.07 * strength;
+            const id = ensureShadowFilter(0, offsetY, blur, alpha);
+            filterAttr = ` filter="url(#${id})"`;
+          }
+        } else {
+          const id = ensureShadowFilter(0, 0, 10, 0.2);
+          filterAttr = ` filter="url(#${id})"`;
         }
         const strokeAttr = isBorderEnabled ? ` stroke="#111827" stroke-width="0.5"` : ` stroke="none" stroke-width="0"`;
-        elements += `<circle cx="${b.x}" cy="${b.y}" r="${b.radius}" fill="${fill}"${strokeAttr} />`;
+        elements += `<circle cx="${b.x}" cy="${b.y}" r="${b.radius}" fill="${fill}"${strokeAttr}${filterAttr} />`;
 
         if (isShineEnabled) {
           const sx = b.x - b.radius * SHINE_OFFSET;
@@ -1531,7 +1575,8 @@
           const ry = b.radius * SHINE_RY;
           const { fill: shineFill, stroke: shineStroke } = shineStyle(b.color);
           const stroke = shineStroke ? ` stroke="${shineStroke}" stroke-width="1"` : '';
-          elements += `<ellipse cx="${sx}" cy="${sy}" rx="${rx}" ry="${ry}" fill="${shineFill}"${stroke} transform="rotate(${SHINE_ROT} ${sx} ${sy})" />`;
+          const shineFilter = shineShadowId ? ` filter="url(#${shineShadowId})"` : '';
+          elements += `<ellipse cx="${sx}" cy="${sy}" rx="${rx}" ry="${ry}" fill="${shineFill}"${stroke}${shineFilter} transform="rotate(${SHINE_ROT} ${sx} ${sy})" />`;
         }
       });