diff --git a/.gitignore b/.gitignore
index 869a74a..e193446 100644
--- a/.gitignore
+++ b/.gitignore
@@ -43,6 +43,7 @@ extension/shared/
 
 # Auto-generated website build output
 website/www/
+website/.avif-cache.json
 
 # Temporary scratch files
 scratch/
diff --git a/package-lock.json b/package-lock.json
index dd0655a..d314241 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -1,12 +1,12 @@
 {
   "name": "koalasync",
-  "version": "2.5.3",
+  "version": "2.5.4",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "koalasync",
-      "version": "2.5.3",
+      "version": "2.5.4",
       "devDependencies": {
         "@playwright/test": "^1.61.1",
         "@vitest/coverage-v8": "^4.1.9",
diff --git a/package.json b/package.json
index 6ff8a85..b72eacc 100644
--- a/package.json
+++ b/package.json
@@ -9,6 +9,7 @@
     "indexnow": "node website/submit-indexnow.cjs",
     "lint": "eslint .",
     "lint:fix": "eslint . --fix",
+    "subset-flags": "node website/tools/subset-flag-font.mjs",
     "test": "npm run verify",
     "test:unit": "vitest run",
     "verify": "node scripts/verify-release.mjs"
diff --git a/website/404.html b/website/404.html
index 3855d1a..c1dcd35 100644
--- a/website/404.html
+++ b/website/404.html
@@ -92,7 +92,7 @@
     <nav>
         <div class="container nav-content">
             <a href="/" class="logo-area" style="text-decoration: none;">
-                <img src="/assets/NewLogoIcon.webp" alt="KoalaSync Logo" width="40" height="40">
+                <img src="/assets/NewLogoIcon_128.webp" alt="KoalaSync Logo" width="40" height="40">
                 <span>KoalaSync</span>
             </a>
             <div class="nav-links">
@@ -111,7 +111,7 @@
     <main class="legal-content">
         <div class="legal-card" data-reveal style="padding: 2.5rem 2rem; text-align: center;">
             <div style="display: flex; justify-content: center;">
-                <img src="/assets/KoalaSearching.webp" alt="A cute koala looking through a telescope, searching for the missing page" class="legal-mascot" width="180" height="180">
+                <img src="/assets/KoalaSearching-180.webp" srcset="/assets/KoalaSearching-180.webp 180w, /assets/KoalaSearching-360.webp 360w" sizes="180px" alt="A cute koala looking through a telescope, searching for the missing page" class="legal-mascot" width="180" height="180">
             </div>
             <h1 style="margin-bottom: 0.5rem;">404</h1>
             <p style="text-transform: uppercase; letter-spacing: 0.1em; font-size: 0.8rem; border-bottom: 1px solid var(--glass-border); padding-bottom: 1.5rem; margin-bottom: 1.5rem;">
diff --git a/website/assets/TwemojiCountryFlags.subset.json b/website/assets/TwemojiCountryFlags.subset.json
new file mode 100644
index 0000000..feaf7c1
--- /dev/null
+++ b/website/assets/TwemojiCountryFlags.subset.json
@@ -0,0 +1,22 @@
+{
+  "comment": "Generated by tools/subset-flag-font.mjs — do not edit. build.cjs fails when site flags and this manifest diverge.",
+  "flags": [
+    "BR",
+    "CN",
+    "DE",
+    "ES",
+    "FR",
+    "GB",
+    "IT",
+    "JP",
+    "KR",
+    "NL",
+    "PL",
+    "PT",
+    "RU",
+    "TR",
+    "UA"
+  ],
+  "sourceFontSha256": "9f04f14429bb6a9f415c7a4dd902a918d7e81a4f7526c415496fdb063954e3b8",
+  "subsetSha256": "d6683cd924e343443effaa96008656e9914c168afad6cd8ac168af79e2b65811"
+}
diff --git a/website/assets/TwemojiCountryFlags.subset.woff2 b/website/assets/TwemojiCountryFlags.subset.woff2
new file mode 100644
index 0000000..c945fab
Binary files /dev/null and b/website/assets/TwemojiCountryFlags.subset.woff2 differ
diff --git a/website/build.cjs b/website/build.cjs
index d037a4f..05a76cf 100644
--- a/website/build.cjs
+++ b/website/build.cjs
@@ -24,7 +24,72 @@ function minifyCSS(code) {
 if (minifyCSS('.parent :is(.a, .b) { color: red; }') !== '.parent :is(.a,.b){color:red}') {
     throw new Error('CSS minifier must preserve descendant combinators before functional pseudo-classes');
 }
-const MIN_AVIF_KB = 0;
+// HTML minifier: comments + indentation only. Newlines are preserved so
+// inline scripts/JSON-LD stay valid; <pre> blocks keep their formatting.
+function minifyHTML(html) {
+    return html.split(/(<pre\b[\s\S]*?<\/pre>)/).map((part, i) => {
+        if (i % 2 === 1) return part;
+        return part
+            .replace(/<!--(?!\[)[\s\S]*?-->/g, '')
+            .replace(/\n[ \t]+/g, '\n')
+            .replace(/\n{2,}/g, '\n');
+    }).join('');
+}
+
+// ── Country-flag font subset (committed artifact, validated here) ────────
+// The subset itself is generated by tools/subset-flag-font.mjs (Python
+// fontTools — the harfbuzz-based JS subsetters drop the COLR/CPAL color
+// tables and produce invisible flags, so the build never subsets itself).
+// This step verifies the committed subset still matches the site and ships
+// it under a content-hashed name.
+function stageFlagFontSubset(websiteDir, wwwDir) {
+    const { collectFlagSourceFiles, extractUsedFlags, flagToCountryCode } = require('./flag-font-utils.cjs');
+    const assetsDir = path.join(websiteDir, 'assets');
+    const subsetPath = path.join(assetsDir, 'TwemojiCountryFlags.subset.woff2');
+    const manifestPath = path.join(assetsDir, 'TwemojiCountryFlags.subset.json');
+    const regenerate = 'run "npm run subset-flags" and commit the result';
+
+    if (!fs.existsSync(subsetPath) || !fs.existsSync(manifestPath)) {
+        throw new Error(`Flag font subset or manifest missing – ${regenerate}`);
+    }
+    const manifest = JSON.parse(fs.readFileSync(manifestPath, 'utf8'));
+    const subset = fs.readFileSync(subsetPath);
+    const sha256 = buf => crypto.createHash('sha256').update(buf).digest('hex');
+    if (sha256(subset) !== manifest.subsetSha256) {
+        throw new Error(`TwemojiCountryFlags.subset.woff2 does not match its manifest – ${regenerate}`);
+    }
+    const sourceFont = fs.readFileSync(path.join(assetsDir, 'TwemojiCountryFlags.woff2'));
+    if (sha256(sourceFont) !== manifest.sourceFontSha256) {
+        throw new Error(`TwemojiCountryFlags.woff2 changed since the subset was generated – ${regenerate}`);
+    }
+
+    const usedFlags = extractUsedFlags(collectFlagSourceFiles(websiteDir));
+    if (usedFlags.length === 0) {
+        throw new Error('Flag extraction found no flag emoji – extraction is broken');
+    }
+    const usedCodes = usedFlags.map(flagToCountryCode);
+    const missing = usedCodes.filter(c => !manifest.flags.includes(c));
+    if (missing.length > 0) {
+        throw new Error(`Flags used on the site but missing from the font subset: ${missing.join(', ')} – ${regenerate}`);
+    }
+    const extra = manifest.flags.filter(c => !usedCodes.includes(c));
+    if (extra.length > 0) {
+        console.warn(`  ⚠️ Subset contains unused flags (${extra.join(', ')}) – "npm run subset-flags" would shrink it.`);
+    }
+
+    const name = `TwemojiCountryFlags.${sha8(subset)}.woff2`;
+    const destAssets = path.join(wwwDir, 'assets');
+    fs.mkdirSync(destAssets, { recursive: true });
+    for (const f of fs.readdirSync(destAssets)) {
+        if (/^TwemojiCountryFlags\.[0-9a-f]{8}\.woff2$/.test(f) && f !== name) {
+            fs.unlinkSync(path.join(destAssets, f));
+        }
+    }
+    fs.writeFileSync(path.join(destAssets, name), subset);
+    const pct = ((1 - subset.length / sourceFont.length) * 100).toFixed(0);
+    console.log(`  Flag font: ${name} (${(subset.length / 1024).toFixed(1)} KB, ${usedCodes.length} flags, -${pct}% vs unsubset)`);
+    return name;
+}
 
 function copyDirSync(src, dest) {
     fs.mkdirSync(dest, { recursive: true });
@@ -57,7 +122,12 @@ function injectAvifPictures(html) {
         const srcsetMatch = attrs.match(/\bsrcset="([^"]*)"/i);
         if (srcsetMatch) {
             const avifSrcset = srcsetMatch[1].replace(/\.webp/gi, '.avif');
-            return `<picture><source srcset="${avifSrcset}" type="image/avif"><img${attrs}></picture>`;
+            // A <source> with width descriptors requires its own sizes
+            // attribute; without it browsers may pick and even reject
+            // candidates (observed as broken images in Chrome).
+            const sizesMatch = attrs.match(/\bsizes="([^"]*)"/i);
+            const sizesAttr = sizesMatch ? ` sizes="${sizesMatch[1]}"` : '';
+            return `<picture><source srcset="${avifSrcset}"${sizesAttr} type="image/avif"><img${attrs}></picture>`;
         }
         return `<picture><source srcset="${avifSrc}" type="image/avif"><img${attrs}></picture>`;
     });
@@ -136,8 +206,15 @@ async function compile() {
         console.warn(`  ⚠️ Warning: ${ogSrc} not found. Skipping og-image generation.`);
     }
 
+    // ── 0.7 Stage the committed flag-font subset (~45% smaller) ──
+    console.log('Staging flag font subset...');
+    const flagFontName = stageFlagFontSubset(websiteDir, wwwDir);
+
     // ── 1. Minify CSS/JS (must happen first so hashes go into HTML) ──
     console.log('Minifying CSS/JS...');
+    // CSS references the hashed subset instead of the raw font file
+    const readStyle = relativePath => fs.readFileSync(path.join(websiteDir, relativePath), 'utf8')
+        .replaceAll('TwemojiCountryFlags.woff2', flagFontName);
     const styleModules = [
         'styles/foundation.css',
         'styles/hero.css',
@@ -170,17 +247,13 @@ async function compile() {
             ]
         }
     ];
-    const styleRaw = styleModules
-        .map(relativePath => fs.readFileSync(path.join(websiteDir, relativePath), 'utf8'))
-        .join('');
+    const styleRaw = styleModules.map(readStyle).join('');
     const styleMin = minifyCSS(styleRaw);
     const styleHash = sha8(styleMin);
     const styleName = `style.${styleHash}.min.css`;
     const styleSRI = sha384(styleMin);
     const compiledLandingBundles = landingBundles.map(bundle => {
-        const raw = bundle.modules
-            .map(relativePath => fs.readFileSync(path.join(websiteDir, relativePath), 'utf8'))
-            .join('');
+        const raw = bundle.modules.map(readStyle).join('');
         const min = minifyCSS(raw);
         return {
             ...bundle,
@@ -476,6 +549,11 @@ async function compile() {
     const destAssets = path.join(wwwDir, 'assets');
     if (fs.existsSync(srcAssets)) {
         copyDirSync(srcAssets, destAssets);
+        // Pages use the hashed subset staged in step 0.7; ship neither the raw
+        // font nor the unhashed subset artifacts
+        fs.rmSync(path.join(destAssets, 'TwemojiCountryFlags.woff2'), { force: true });
+        fs.rmSync(path.join(destAssets, 'TwemojiCountryFlags.subset.woff2'), { force: true });
+        fs.rmSync(path.join(destAssets, 'TwemojiCountryFlags.subset.json'), { force: true });
         console.log('  Assets copied.');
     }
 
@@ -487,20 +565,49 @@ async function compile() {
         console.log('  ✓ Apple touch icons copied to www root.');
     }
 
+    // ── 6.5 Responsive variants for the static-page mascots ──
+    // These pages showed 434-500px sources at 180px CSS (2x need: 360px).
+    // Variants feed the AVIF step below and the srcset attributes in the
+    // static HTML files.
+    console.log('Generating responsive mascot variants...');
+    const RESPONSIVE_VARIANTS = [
+        { src: 'KoalaImprintl.webp', widths: [180, 360] },
+        { src: 'KoalaPrivacy.webp', widths: [180, 360] },
+        { src: 'KoalaSearching.webp', widths: [180, 360] }
+    ];
+    for (const variant of RESPONSIVE_VARIANTS) {
+        const variantSrc = path.join(destAssets, variant.src);
+        if (!fs.existsSync(variantSrc)) {
+            throw new Error(`Responsive variant source ${variant.src} not found in assets`);
+        }
+        for (const width of variant.widths) {
+            const out = variantSrc.replace(/\.webp$/, `-${width}.webp`);
+            await sharp(variantSrc).resize({ width }).toFile(out);
+        }
+    }
+
     // ── 7. Convert all WebP to AVIF (quality 65) ──
+    // Content-hash cache: mtime comparison never hit because copyDirSync
+    // refreshes mtimes, so every verify re-encoded all AVIFs.
     console.log('Converting WebP → AVIF...');
-    let avifCount = 0;
+    const AVIF_OPTS = { quality: 65, speed: 4 };
+    const avifCachePath = path.join(websiteDir, '.avif-cache.json');
+    let avifCache = {};
+    try { avifCache = JSON.parse(fs.readFileSync(avifCachePath, 'utf8')); } catch { /* cold cache */ }
+    const avifCacheNext = {};
+    let avifCount = 0, avifCachedCount = 0;
     const webpFiles = fs.readdirSync(destAssets).filter(f => f.endsWith('.webp'));
     for (const f of webpFiles) {
         const src = path.join(destAssets, f);
-        const stat = fs.statSync(src);
-        if (stat.size < MIN_AVIF_KB * 1024) continue;
         const dest = path.join(destAssets, f.replace(/\.webp$/, '.avif'));
-        if (fs.existsSync(dest) && fs.statSync(dest).mtimeMs >= stat.mtimeMs) continue;
-        await sharp(src).avif({ quality: 65, speed: 4 }).toFile(dest);
+        const key = `${sha8(fs.readFileSync(src))}:q${AVIF_OPTS.quality}s${AVIF_OPTS.speed}`;
+        avifCacheNext[f] = key;
+        if (avifCache[f] === key && fs.existsSync(dest)) { avifCachedCount++; continue; }
+        await sharp(src).avif(AVIF_OPTS).toFile(dest);
         avifCount++;
     }
-    console.log(`  ${avifCount} AVIF files generated.`);
+    fs.writeFileSync(avifCachePath, JSON.stringify(avifCacheNext, null, 2) + '\n');
+    console.log(`  ${avifCount} AVIF files generated, ${avifCachedCount} unchanged (cache).`);
 
     // ── 8. Post-process ALL HTML files ──
     console.log('Post-processing HTML...');
@@ -540,6 +647,22 @@ async function compile() {
         // 8c. Minify inline SVGs
         html = minifyInlineSvgs(html);
 
+        // 8d. Preload the subset flag font on pages that show flags. This
+        // cuts the HTML→CSS→font chain; unicode-range alone would delay the
+        // request until after CSS parse + layout.
+        if (/[\u{1F1E6}-\u{1F1FF}]{2}/u.test(html)) {
+            const relDir = path.relative(wwwDir, path.dirname(filePath));
+            // 404.html is served for arbitrary URLs and must use absolute paths
+            const prefix = path.basename(filePath) === '404.html'
+                ? '/'
+                : (relDir ? '../'.repeat(relDir.split(path.sep).length) : '');
+            const preload = `<link rel="preload" as="font" type="font/woff2" href="${prefix}assets/${flagFontName}" crossorigin>`;
+            html = html.replace('</head>', `${preload}\n</head>`);
+        }
+
+        // 8e. Minify HTML (comments + indentation)
+        html = minifyHTML(html);
+
         fs.writeFileSync(filePath, html);
     });
 
diff --git a/website/datenschutz-de.html b/website/datenschutz-de.html
index 7df088c..50d75d9 100644
--- a/website/datenschutz-de.html
+++ b/website/datenschutz-de.html
@@ -121,7 +121,7 @@
     <nav>
         <div class="container nav-content">
             <a href="./" class="logo-area" style="text-decoration: none;">
-                <img src="../assets/NewLogoIcon.webp" alt="KoalaSync Logo" width="40" height="40">
+                <img src="../assets/NewLogoIcon_128.webp" alt="KoalaSync Logo" width="40" height="40">
                 <span>KoalaSync</span>
             </a>
             <div class="nav-links">
@@ -161,7 +161,7 @@
     <main class="legal-content">
         <div class="legal-card" data-reveal style="padding: 2rem;">
             <div style="display: flex; justify-content: center;">
-                <img src="../assets/KoalaPrivacy.webp" alt="Niedlicher Koala, der den Datenschutz repräsentiert" class="legal-mascot" width="180" height="180">
+                <img src="../assets/KoalaPrivacy-180.webp" srcset="../assets/KoalaPrivacy-180.webp 180w, ../assets/KoalaPrivacy-360.webp 360w" sizes="180px" alt="Niedlicher Koala, der den Datenschutz repräsentiert" class="legal-mascot" width="180" height="180">
             </div>
             <h1>Datenschutz</h1>
             <p style="text-align: center; text-transform: uppercase; letter-spacing: 0.1em; font-size: 0.8rem; border-bottom: 1px solid var(--glass-border); padding-bottom: 1.5rem; margin-bottom: 2rem;">
diff --git a/website/flag-font-utils.cjs b/website/flag-font-utils.cjs
new file mode 100644
index 0000000..95b6b1a
--- /dev/null
+++ b/website/flag-font-utils.cjs
@@ -0,0 +1,48 @@
+/**
+ * Shared helpers for the country-flag font subset.
+ * Used by build.cjs (validation) and tools/subset-flag-font.mjs (generation).
+ *
+ * Flags are regional-indicator pairs; tag-sequence flags (🏴 England etc.)
+ * are NOT extracted or subset — if one is ever added it will render via the
+ * system emoji font.
+ */
+const fs = require('fs');
+const path = require('path');
+
+const FLAG_PAIR_RE = /[\u{1F1E6}-\u{1F1FF}]{2}/gu;
+
+function collectFlagSourceFiles(websiteDir) {
+    const files = [];
+    for (const entry of fs.readdirSync(websiteDir)) {
+        if (entry.endsWith('.html')) files.push(path.join(websiteDir, entry));
+    }
+    for (const dir of ['alternatives', 'locales']) {
+        const p = path.join(websiteDir, dir);
+        if (!fs.existsSync(p)) continue;
+        for (const entry of fs.readdirSync(p)) {
+            if (/\.(html|json)$/.test(entry)) files.push(path.join(p, entry));
+        }
+    }
+    return files;
+}
+
+function extractUsedFlags(files) {
+    const flags = new Set();
+    for (const file of files) {
+        for (const m of fs.readFileSync(file, 'utf8').matchAll(FLAG_PAIR_RE)) {
+            flags.add(m[0]);
+        }
+    }
+    return [...flags].sort();
+}
+
+// 🇩🇪 → "DE" (for readable manifests and tool output)
+function flagToCountryCode(flag) {
+    return [...flag].map(c => String.fromCharCode(c.codePointAt(0) - 0x1F1E6 + 65)).join('');
+}
+
+function countryCodeToFlag(code) {
+    return [...code].map(c => String.fromCodePoint(0x1F1E6 + c.charCodeAt(0) - 65)).join('');
+}
+
+module.exports = { FLAG_PAIR_RE, collectFlagSourceFiles, extractUsedFlags, flagToCountryCode, countryCodeToFlag };
diff --git a/website/impressum-de.html b/website/impressum-de.html
index 9b54bf5..d10c6dd 100644
--- a/website/impressum-de.html
+++ b/website/impressum-de.html
@@ -121,7 +121,7 @@
     <nav>
         <div class="container nav-content">
             <a href="./" class="logo-area" style="text-decoration: none;">
-                <img src="../assets/NewLogoIcon.webp" alt="KoalaSync Logo" width="40" height="40">
+                <img src="../assets/NewLogoIcon_128.webp" alt="KoalaSync Logo" width="40" height="40">
                 <span>KoalaSync</span>
             </a>
             <div class="nav-links">
@@ -161,7 +161,7 @@
     <main class="legal-content">
         <div class="legal-card" data-reveal style="padding: 2rem;">
             <div style="display: flex; justify-content: center;">
-                <img src="../assets/KoalaImprintl.webp" alt="Niedlicher Koala, der das Impressum repräsentiert" class="legal-mascot" width="180" height="180">
+                <img src="../assets/KoalaImprintl-180.webp" srcset="../assets/KoalaImprintl-180.webp 180w, ../assets/KoalaImprintl-360.webp 360w" sizes="180px" alt="Niedlicher Koala, der das Impressum repräsentiert" class="legal-mascot" width="180" height="180">
             </div>
             <h1>Impressum / Anbieterinformationen</h1>
             <p style="text-align: center; text-transform: uppercase; letter-spacing: 0.1em; font-size: 0.8rem; border-bottom: 1px solid var(--glass-border); padding-bottom: 1.5rem; margin-bottom: 2rem;">
diff --git a/website/imprint.html b/website/imprint.html
index 6aeb49a..e0696a1 100644
--- a/website/imprint.html
+++ b/website/imprint.html
@@ -121,7 +121,7 @@
     <nav>
         <div class="container nav-content">
             <a href="./" class="logo-area" style="text-decoration: none;">
-                <img src="assets/NewLogoIcon.webp" alt="KoalaSync Logo" width="40" height="40">
+                <img src="assets/NewLogoIcon_128.webp" alt="KoalaSync Logo" width="40" height="40">
                 <span>KoalaSync</span>
             </a>
             <div class="nav-links">
@@ -161,7 +161,7 @@
     <main class="legal-content">
         <div class="legal-card" data-reveal style="padding: 2rem;">
             <div style="display: flex; justify-content: center;">
-                <img src="assets/KoalaImprintl.webp" alt="Cute Koala representing the legal notice page" class="legal-mascot" width="180" height="180">
+                <img src="assets/KoalaImprintl-180.webp" srcset="assets/KoalaImprintl-180.webp 180w, assets/KoalaImprintl-360.webp 360w" sizes="180px" alt="Cute Koala representing the legal notice page" class="legal-mascot" width="180" height="180">
             </div>
             <h1>Legal Notice</h1>
             <p style="text-align: center; text-transform: uppercase; letter-spacing: 0.1em; font-size: 0.8rem; border-bottom: 1px solid var(--glass-border); padding-bottom: 1.5rem; margin-bottom: 2rem;">
diff --git a/website/join.html b/website/join.html
index 93a0ccd..449662b 100644
--- a/website/join.html
+++ b/website/join.html
@@ -106,7 +106,7 @@
     <nav>
         <div class="container nav-content">
             <a href="./" class="logo-area" style="text-decoration: none;">
-                <img src="assets/NewLogoIcon.webp" alt="KoalaSync Logo" width="64" height="64">
+                <img src="assets/NewLogoIcon_128.webp" alt="KoalaSync Logo" width="64" height="64">
                 <span>KoalaSync</span>
             </a>
             <div class="nav-links" id="primary-nav" role="navigation" aria-label="Primary">
@@ -155,8 +155,8 @@
             <div class="join-status-visual">
                 <div class="status-ring active-pulse" id="status-ring"></div>
                 <div id="join-status-icon" style="z-index: 2; transition: transform 0.3s cubic-bezier(0.175, 0.885, 0.32, 1.275); display: flex; align-items: center; justify-content: center;">
-                    <img src="assets/KoalaSearching.webp" alt="A cute koala looking through a telescope searching for your extension" class="join-status-mascot searching-mascot join-status-pulse" lang="en">
-                    <img src="assets/KoalaSearching.webp" alt="Ein niedlicher Koala schaut durch ein Fernrohr und sucht nach deiner Erweiterung" class="join-status-mascot searching-mascot join-status-pulse" lang="de">
+                    <img src="assets/KoalaSearching-180.webp" srcset="assets/KoalaSearching-180.webp 180w, assets/KoalaSearching-360.webp 360w" sizes="175px" alt="A cute koala looking through a telescope searching for your extension" class="join-status-mascot searching-mascot join-status-pulse" lang="en">
+                    <img src="assets/KoalaSearching-180.webp" srcset="assets/KoalaSearching-180.webp 180w, assets/KoalaSearching-360.webp 360w" sizes="175px" alt="Ein niedlicher Koala schaut durch ein Fernrohr und sucht nach deiner Erweiterung" class="join-status-mascot searching-mascot join-status-pulse" lang="de">
                 </div>
             </div>
 
diff --git a/website/privacy.html b/website/privacy.html
index 084bc56..642ac2c 100644
--- a/website/privacy.html
+++ b/website/privacy.html
@@ -121,7 +121,7 @@
     <nav>
         <div class="container nav-content">
             <a href="./" class="logo-area" style="text-decoration: none;">
-                <img src="assets/NewLogoIcon.webp" alt="KoalaSync Logo" width="40" height="40">
+                <img src="assets/NewLogoIcon_128.webp" alt="KoalaSync Logo" width="40" height="40">
                 <span>KoalaSync</span>
             </a>
             <div class="nav-links">
@@ -161,7 +161,7 @@
     <main class="legal-content">
         <div class="legal-card" data-reveal style="padding: 2rem;">
             <div style="display: flex; justify-content: center;">
-                <img src="assets/KoalaPrivacy.webp" alt="Cute Koala representing privacy and data security" class="legal-mascot" width="180" height="180">
+                <img src="assets/KoalaPrivacy-180.webp" srcset="assets/KoalaPrivacy-180.webp 180w, assets/KoalaPrivacy-360.webp 360w" sizes="180px" alt="Cute Koala representing privacy and data security" class="legal-mascot" width="180" height="180">
             </div>
             <h1>Privacy Policy</h1>
             <p style="text-align: center; text-transform: uppercase; letter-spacing: 0.1em; font-size: 0.8rem; border-bottom: 1px solid var(--glass-border); padding-bottom: 1.5rem; margin-bottom: 2rem;">
diff --git a/website/styles/foundation.css b/website/styles/foundation.css
index a5d7ccb..d6773ad 100644
--- a/website/styles/foundation.css
+++ b/website/styles/foundation.css
@@ -2,7 +2,10 @@
 
 @font-face {
     font-family: 'Twemoji Country Flags';
-    unicode-range: U+1F1E6-1F1FF, U+1F3F4, U+E0062-E0063, U+E0065, U+E0067, U+E006C, U+E006E, U+E0073-E0074, U+E0077, U+E007F;
+    /* Regional-indicator pairs only: the build subsets this font to the
+       flags actually used. Tag-sequence flags (U+1F3F4 + tags) are not in
+       the subset and must fall through to the system emoji font. */
+    unicode-range: U+1F1E6-1F1FF;
     src: url('assets/TwemojiCountryFlags.woff2') format('woff2');
     font-display: swap;
 }
diff --git a/website/template.html b/website/template.html
index d39448d..ce9964b 100644
--- a/website/template.html
+++ b/website/template.html
@@ -416,7 +416,7 @@
                             <span class="demo-tab-title"><svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" width="11" height="11" aria-hidden="true"><rect x="2" y="3" width="20" height="14" rx="2"/><path d="M8 21h8M12 17v4"/></svg> <span class="demo-title-text-ep1">Stranger Things - S4E1</span></span>
                             <span class="demo-tab-user demo-user-a">🐱 ChillCat</span>
                             <button class="demo-ext-launcher" id="demo-launcher" type="button" aria-expanded="true" title="Open or close the KoalaSync popup">
-                                <img src="{{ASSET_PATH}}assets/NewLogoIcon.webp" alt="" width="16" height="16" loading="eager" decoding="async">
+                                <img src="{{ASSET_PATH}}assets/NewLogoIcon_64.webp" alt="" width="16" height="16" loading="eager" decoding="async">
                             </button>
                         </div>
                         <div class="demo-video">
@@ -504,7 +504,7 @@
                             <span class="demo-tab-title"><svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" width="11" height="11" aria-hidden="true"><rect x="2" y="3" width="20" height="14" rx="2"/><path d="M8 21h8M12 17v4"/></svg> <span class="demo-title-text-ep1">Stranger Things - S4E1</span></span>
                             <span class="demo-tab-user demo-user-b">🐶 HappyDog</span>
                             <span class="demo-ext-launcher demo-ext-static" aria-hidden="true" title="KoalaSync is installed here too">
-                                <img src="{{ASSET_PATH}}assets/NewLogoIcon.webp" alt="" width="16" height="16" loading="eager" decoding="async">
+                                <img src="{{ASSET_PATH}}assets/NewLogoIcon_64.webp" alt="" width="16" height="16" loading="eager" decoding="async">
                             </span>
                         </div>
                         <div class="demo-video">
@@ -591,7 +591,7 @@
 
                 <div class="extension-mockup">
                     <div class="mock-header-row">
-                        <div class="mock-header-title"><img src="{{ASSET_PATH}}assets/NewLogoIcon.webp" alt="KoalaSync Logo">KoalaSync</div>
+                        <div class="mock-header-title"><img src="{{ASSET_PATH}}assets/NewLogoIcon_64.webp" alt="KoalaSync Logo">KoalaSync</div>
                         <a href="https://github.com/Shik3i/KoalaSync" target="_blank" rel="noopener" class="mock-version-link" title="Visit GitHub Repository">
                             <svg viewBox="0 0 16 16" fill="currentColor" style="width: 12px; height: 12px; display: block;"><path d="M8 0C3.58 0 0 3.58 0 8c0 3.54 2.29 6.53 5.47 7.59.4.07.55-.17.55-.38 0-.19-.01-.82-.01-1.49-2.01.37-2.53-.49-2.69-.94-.09-.23-.48-.94-.82-1.13-.28-.15-.68-.52-.01-.53.63-.01 1.08.58 1.23.82.72 1.21 1.87.87 2.33.66.07-.52.28-.87.51-1.07-1.78-.2-3.64-.89-3.64-3.95 0-.87.31-1.59.82-2.15-.08-.2-.36-1.02.08-2.12 0 0 .67-.21 2.2.82.64-.18 1.32-.27 2-.27.68 0 1.36.09 2 .27 1.53-1.04 2.2-.82 2.2-.82.44 1.1.16 1.92.08 2.12.51.56.82 1.27.82 2.15 0 3.07-1.87 3.75-3.65 3.95.29.25.54.73.54 1.48 0 1.07-.01 1.93-.01 2.2 0 .21.15.46.55.38A8.013 8.013 0 0016 8c0-4.42-3.58-8-8-8z"/></svg>
                             <span class="mockup-version">{{VERSION}}</span>
@@ -611,7 +611,7 @@
                         <div id="mock-room" class="mock-screen active">
                             <!-- Pre-room state, shown only during the scripted walkthrough -->
                             <div id="demo-room-empty" class="demo-room-empty">
-                                <img src="{{ASSET_PATH}}assets/NewLogoIcon.webp" alt="" width="42" height="42" loading="eager" decoding="async">
+                                <img src="{{ASSET_PATH}}assets/NewLogoIcon_128.webp" alt="" width="42" height="42" loading="eager" decoding="async">
                                 <div class="demo-room-empty-text">{{DEMO_NO_ROOM}}</div>
                                 <button id="demo-create-room" class="demo-create-room-btn" type="button">{{DEMO_CREATE_ROOM}}</button>
                             </div>
@@ -1139,7 +1139,7 @@
                         <div class="illus-popup-card">
                             <div class="illus-popup-header">
                                 <div class="illus-popup-brand">
-                                    <img src="{{ASSET_PATH}}assets/NewLogoIcon.webp" alt="KoalaSync Logo" width="14" height="14">
+                                    <img src="{{ASSET_PATH}}assets/NewLogoIcon_64.webp" alt="KoalaSync Logo" width="14" height="14">
                                     <span>KoalaSync</span>
                                 </div>
                                 <div class="illus-popup-version mockup-version">{{VERSION}}</div>
@@ -1185,7 +1185,7 @@
                         <div class="illus-popup-card">
                             <div class="illus-popup-header">
                                 <div class="illus-popup-brand">
-                                    <img src="{{ASSET_PATH}}assets/NewLogoIcon.webp" alt="KoalaSync Logo" width="14" height="14">
+                                    <img src="{{ASSET_PATH}}assets/NewLogoIcon_64.webp" alt="KoalaSync Logo" width="14" height="14">
                                     <span>KoalaSync</span>
                                 </div>
                                 <div class="illus-popup-version mockup-version">{{VERSION}}</div>
diff --git a/website/tools/subset-flag-font.mjs b/website/tools/subset-flag-font.mjs
new file mode 100644
index 0000000..78cf4a0
--- /dev/null
+++ b/website/tools/subset-flag-font.mjs
@@ -0,0 +1,73 @@
+#!/usr/bin/env node
+/**
+ * Regenerate the committed country-flag font subset.
+ *
+ *   npm run subset-flags       (or: node website/tools/subset-flag-font.mjs)
+ *
+ * Extracts every flag emoji used in website HTML/locales, subsets
+ * assets/TwemojiCountryFlags.woff2 down to exactly those flags via Python
+ * fontTools (harfbuzz-based JS subsetters drop the COLR color tables and
+ * produce invisible flags), and writes:
+ *
+ *   assets/TwemojiCountryFlags.subset.woff2   (committed)
+ *   assets/TwemojiCountryFlags.subset.json    (committed manifest)
+ *
+ * The website build (build.cjs) is pure Node: it only validates the
+ * manifest and fails when a flag was added without re-running this tool.
+ *
+ * Requires python3 with fonttools + brotli. Override the interpreter with
+ * the PYTHON env var, e.g. PYTHON=.venv/bin/python npm run subset-flags
+ */
+import { execFileSync } from 'node:child_process';
+import crypto from 'node:crypto';
+import fs from 'node:fs';
+import path from 'node:path';
+import { fileURLToPath } from 'node:url';
+import { createRequire } from 'node:module';
+
+const require = createRequire(import.meta.url);
+const websiteDir = path.resolve(path.dirname(fileURLToPath(import.meta.url)), '..');
+const { collectFlagSourceFiles, extractUsedFlags, flagToCountryCode } = require(path.join(websiteDir, 'flag-font-utils.cjs'));
+
+const sourceFont = path.join(websiteDir, 'assets', 'TwemojiCountryFlags.woff2');
+const outputFont = path.join(websiteDir, 'assets', 'TwemojiCountryFlags.subset.woff2');
+const manifestPath = path.join(websiteDir, 'assets', 'TwemojiCountryFlags.subset.json');
+
+const python = process.env.PYTHON || 'python3';
+try {
+    execFileSync(python, ['-c', 'import fontTools.subset, brotli'], { stdio: 'pipe' });
+} catch {
+    console.error(`error: ${python} lacks fonttools/brotli.`);
+    console.error('Install them (e.g. "pip3 install fonttools brotli") or point PYTHON at an interpreter that has them:');
+    console.error('  PYTHON=/path/to/venv/bin/python npm run subset-flags');
+    process.exit(1);
+}
+
+const flags = extractUsedFlags(collectFlagSourceFiles(websiteDir));
+if (flags.length === 0) {
+    console.error('error: no flag emoji found in website sources — extraction is broken');
+    process.exit(1);
+}
+const codes = flags.map(flagToCountryCode);
+console.log(`Found ${codes.length} flags: ${codes.join(' ')}`);
+
+execFileSync(python, [
+    path.join(websiteDir, 'tools', 'subset_flag_font.py'),
+    sourceFont,
+    outputFont,
+    codes.join(',')
+], { stdio: 'inherit' });
+
+const sha = buf => crypto.createHash('sha256').update(buf).digest('hex');
+const manifest = {
+    comment: 'Generated by tools/subset-flag-font.mjs — do not edit. build.cjs fails when site flags and this manifest diverge.',
+    flags: codes,
+    sourceFontSha256: sha(fs.readFileSync(sourceFont)),
+    subsetSha256: sha(fs.readFileSync(outputFont))
+};
+fs.writeFileSync(manifestPath, JSON.stringify(manifest, null, 2) + '\n');
+
+const before = fs.statSync(sourceFont).size;
+const after = fs.statSync(outputFont).size;
+console.log(`Wrote ${path.relative(process.cwd(), outputFont)} (${(after / 1024).toFixed(1)} KB, -${((1 - after / before) * 100).toFixed(0)}% vs source) + manifest.`);
+console.log('Commit both files.');
diff --git a/website/tools/subset_flag_font.py b/website/tools/subset_flag_font.py
new file mode 100644
index 0000000..dd4251d
--- /dev/null
+++ b/website/tools/subset_flag_font.py
@@ -0,0 +1,90 @@
+"""Subset TwemojiCountryFlags.woff2 to the given country flags.
+
+Invoked by subset-flag-font.mjs — do not run directly unless debugging:
+    python3 subset_flag_font.py <source.woff2> <output.woff2> DE,FR,GB,...
+
+Requires: fonttools, brotli (pip install fonttools brotli).
+
+harfbuzz-based JS subsetters (subset-font/harfbuzzjs) silently drop the
+COLR/CPAL color tables of this font, producing invisible flags — fontTools
+subsets them correctly. Each requested flag is validated to have a GSUB
+ligature AND COLR color layers so a broken subset can never be emitted.
+"""
+import io
+import sys
+
+from fontTools import subset
+from fontTools.ttLib import TTFont
+
+
+def flag_codepoints(code):
+    return [0x1F1E6 + ord(ch) - ord("A") for ch in code]
+
+
+def ligature_glyph(font, first, second):
+    """Return the GSUB ligature glyph for a regional-indicator pair."""
+    gsub = font["GSUB"].table
+    for lookup in gsub.LookupList.Lookup:
+        subtables = []
+        if lookup.LookupType == 4:
+            subtables = lookup.SubTable
+        elif lookup.LookupType == 7:  # extension
+            subtables = [st.ExtSubTable for st in lookup.SubTable if st.ExtensionLookupType == 4]
+        for st in subtables:
+            for lig in st.ligatures.get(first, []):
+                if lig.Component == [second]:
+                    return lig.LigGlyph
+    return None
+
+
+def main():
+    src_path, out_path, codes_arg = sys.argv[1], sys.argv[2], sys.argv[3]
+    codes = sorted(codes_arg.split(","))
+
+    font = TTFont(src_path)
+    if "COLR" not in font or "CPAL" not in font:
+        sys.exit("source font has no COLR/CPAL tables")
+
+    text = "".join(chr(cp) for code in codes for cp in flag_codepoints(code))
+    options = subset.Options()
+    options.flavor = "woff2"
+    subsetter = subset.Subsetter(options=options)
+    subsetter.populate(text=text)
+    subsetter.subset(font)
+
+    buf = io.BytesIO()
+    font.save(buf)
+    result = TTFont(io.BytesIO(buf.getvalue()))
+
+    for table in ("COLR", "CPAL", "GSUB", "cmap"):
+        if table not in result:
+            sys.exit(f"subset lost the {table} table")
+
+    cmap = result.getBestCmap()
+    glyph_name = {}
+    for code in codes:
+        for cp in flag_codepoints(code):
+            if cp not in cmap:
+                sys.exit(f"flag {code}: regional indicator U+{cp:X} missing from subset cmap")
+        first, second = (cmap[cp] for cp in flag_codepoints(code))
+        lig = ligature_glyph(result, first, second)
+        if lig is None:
+            sys.exit(f"flag {code}: no GSUB ligature in subset — font has no artwork for it")
+        glyph_name[code] = lig
+
+    colr = result["COLR"]
+    if colr.version == 0:
+        for code, lig in glyph_name.items():
+            if not colr.ColorLayers.get(lig):
+                sys.exit(f"flag {code}: ligature glyph {lig} has no COLR color layers")
+    # COLR v1 would need different traversal; Twemoji country flags is v0
+    elif colr.version != 0:
+        sys.exit(f"unexpected COLR version {colr.version} — validation only supports v0")
+
+    with open(out_path, "wb") as f:
+        f.write(buf.getvalue())
+    print(f"subset OK: {len(codes)} flags, {len(buf.getvalue())} bytes")
+
+
+if __name__ == "__main__":
+    main()