diff --git a/.gitignore b/.gitignore
index 0db01f3..e286330 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,2 +1,4 @@
 node_modules
+examples
 run.sh
+screenshot*
diff --git a/index.js b/index.js
index a0eea3f..de49a90 100644
--- a/index.js
+++ b/index.js
@@ -3,10 +3,43 @@
 const fs = require('fs').promises;
 const process = require('process');
 const puppeteer = require('puppeteer');
+const quality = require('./quality.js');
 
 // Size of the rendering of the web page
 const size = { width: 1280, height: 720 };
 
+// Logging helper
+function write(stream, chunk, encoding='utf8') {
+    return new Promise((resolve, reject) => {
+        const errListener = (err) => {
+            stream.removeListener('error', errListener);
+            reject(err);
+        };
+        stream.addListener('error', errListener);
+        const callback = () => {
+            stream.removeListener('error', errListener);
+            resolve(undefined);
+        };
+        stream.write(chunk, encoding, callback);
+    });
+}
+
+async function print(data) {
+    await write(process.stdout, data);
+}
+
+async function eprint(data) {
+    await write(process.stderr, data);
+}
+
+async function println(data) {
+    await write(process.stdout, data + '\n');
+}
+
+async function eprintln(data) {
+    await write(process.stderr, data + '\n');
+}
+
 async function main() {
 
     if (process.argv[2] === undefined) {
@@ -57,9 +90,17 @@ async function main() {
     let file2 = await fs.readFile(__dirname + '/' + 'screenshot2.png');
     let filesAreSame = file1.map((x, i) => x === file2[i]).reduce((a, b) => a && b, true);
 
-    // Crash if they're different
     if (!filesAreSame) {
-        throw new Error("Page edit changed the layout");
+        // Check psnr
+        let psnr = await quality.psnr(__dirname + '/' + 'screenshot1.png', __dirname + '/' + 'screenshot2.png');
+
+        // Crash if they're different
+        if (psnr > 70) {
+            eprintln("\x1b[33mWarning: " + process.argv[2] + " produced slight diff: psnr = " + psnr + '\x1b[0m');
+        } else {
+            await eprintln("\x1b[31mError: age edit changed the layout: psnr = " + psnr + '\x1b[0m');
+            process.exit(1);
+        }
     }
 
     // Analyse the root and output the result
@@ -82,14 +123,19 @@ async function addSpan(element) {
     for (let elt of elts) {
         let value = await elt.evaluate(el => el.textContent, element);
         if (value !== "") {
-            await elt.evaluate(el => {
-                if (el.innerHTML.indexOf('<li>') === -1) {
+            let html = await elt.evaluate(el => {
+                if (el.innerHTML.indexOf('<li>') === -1 && el.innerHTML.indexOf('<p>') === -1) {
+                    let tmp = el.innerHTML;
                     el.innerHTML = '<span class="sized-span">' + el.innerHTML + '</span>';
-                    return true;
+                    return [tmp, el.innerHTML];
                 } else {
-                    return false;
+                    return null;
                 }
             });
+
+            if (html !== null) {
+                await eprintln("\x1b[36mReplaced " + JSON.stringify(html[0]) + " by " + JSON.stringify(html[1]) + '\x1b[0m');
+            }
         }
     }
 
diff --git a/package-lock.json b/package-lock.json
index 6ccb661..0024732 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -9,6 +9,7 @@
       "version": "1.0.0",
       "license": "ISC",
       "dependencies": {
+        "pngjs": "^7.0.0",
         "puppeteer": "^19.7.1"
       },
       "bin": {
@@ -48,9 +49,9 @@
       }
     },
     "node_modules/@types/node": {
-      "version": "18.13.0",
-      "resolved": "https://registry.npmjs.org/@types/node/-/node-18.13.0.tgz",
-      "integrity": "sha512-gC3TazRzGoOnoKAhUx+Q0t8S9Tzs74z7m0ipwGpSqQrleP14hKxP4/JUeEQcD3W1/aIpnWl8pHowI7WokuZpXg==",
+      "version": "18.14.0",
+      "resolved": "https://registry.npmjs.org/@types/node/-/node-18.14.0.tgz",
+      "integrity": "sha512-5EWrvLmglK+imbCJY0+INViFWUHg1AHel1sq4ZVSfdcNqGy9Edv3UB9IIzzg+xPaUcAgZYcfVs2fBcwDeZzU0A==",
       "optional": true
     },
     "node_modules/@types/yauzl": {
@@ -540,6 +541,14 @@
       "resolved": "https://registry.npmjs.org/pend/-/pend-1.2.0.tgz",
       "integrity": "sha512-F3asv42UuXchdzt+xXqfW1OGlVBe+mxa2mqI0pg5yAHZPvFmY3Y6drSf/GQ1A86WgWEN9Kzh/WrgKa6iGcHXLg=="
     },
+    "node_modules/pngjs": {
+      "version": "7.0.0",
+      "resolved": "https://registry.npmjs.org/pngjs/-/pngjs-7.0.0.tgz",
+      "integrity": "sha512-LKWqWJRhstyYo9pGvgor/ivk2w94eSjE3RGVuzLGlr3NmD8bf7RcYGze1mNdEHRP6TRP6rMuDHk5t44hnTRyow==",
+      "engines": {
+        "node": ">=14.19.0"
+      }
+    },
     "node_modules/progress": {
       "version": "2.0.3",
       "resolved": "https://registry.npmjs.org/progress/-/progress-2.0.3.tgz",
diff --git a/package.json b/package.json
index 06e6325..7489186 100644
--- a/package.json
+++ b/package.json
@@ -10,6 +10,7 @@
   "author": "",
   "license": "ISC",
   "dependencies": {
+    "pngjs": "^7.0.0",
     "puppeteer": "^19.7.1"
   }
 }
diff --git a/quality.js b/quality.js
new file mode 100644
index 0000000..53a7b54
--- /dev/null
+++ b/quality.js
@@ -0,0 +1,65 @@
+const { PNG } = require('pngjs');
+const fs = require('fs');
+
+// Fixed from https://www.npmjs.com/package/png-quality
+
+async function loadPngFile(pathOrBuffer) {
+    // Load buffer of path
+    if (!(pathOrBuffer instanceof Buffer)) {
+        pathOrBuffer = await new Promise((resolve, reject) => {
+            fs.readFile(pathOrBuffer, (err, data) => {
+                if (err) return reject(err)
+                resolve(data)
+            });
+        })
+    }
+
+    // Load PNG from buffer
+    return await new Promise((resolve, reject) => {
+        const png = new PNG()
+        png.parse(pathOrBuffer, err => {
+            if (err) return reject(err)
+            resolve(png)
+        })
+    })
+}
+
+async function mse(png1, png2) {
+    const pngs = [png1, png2];
+    for (let i in pngs) {
+        if (!(pngs[i] instanceof PNG)) pngs[i] = await loadPngFile(pngs[i])
+    }
+
+    if (pngs[0].width !== pngs[1].width || pngs[0].height !== pngs[1].height) {
+        throw new Error('Width or height does not equal')
+    }
+
+    if (pngs[0].data.length !== pngs[1].data.length) {
+        throw new Error('Data buffer length does not equal')
+    }
+
+    const square = (a) => a * a,
+        channelIndex = [0, 1, 2],
+        channelMax = 255 * 255,
+        area = pngs[0].width * pngs[1].height
+
+    let mse = 0
+    for (let i = 0; i < pngs[0].data.length; i += 4) {
+        const rgbas = pngs.map(png => png.data.slice(i, i + 4))
+        const rgbs = rgbas.map(rgba => channelIndex.map(i => rgba[i] * rgba[3]))
+        channelIndex.forEach(i => mse += square(rgbs[0][i] - rgbs[1][i]))
+    }
+
+    return mse / 3.0 / (channelMax * channelMax) / area
+}
+
+async function psnr(png1, png2) {
+    const m = await mse(png1, png2)
+    return 10 * Math.log10(1 / m)
+}
+
+module.exports = {
+    loadPngFile,
+    mse,
+    psnr,
+};