diff --git a/src/core/operations/VigenèreEncode.mjs b/src/core/operations/VigenèreEncode.mjs
index db212fe2..effcb0c6 100644
--- a/src/core/operations/VigenèreEncode.mjs
+++ b/src/core/operations/VigenèreEncode.mjs
@@ -39,36 +39,30 @@ class VigenèreEncode extends Operation {
      * @returns {string}
      */
     run(input, args) {
-        const alphabet = "abcdefghijklmnopqrstuvwxyz",
-            key = args[0].toLowerCase();
-        let output = "",
-            fail = 0,
-            keyIndex,
-            msgIndex,
-            chr;
+        const alphabet = "abcdefghijklmnopqrstuvwxyz0123456789";
+        const key = args[0].toLowerCase();
+        let output = "";
+        let fail = 0;
+        let keyIndex, msgIndex, chr;
 
         if (!key) throw new OperationError("No key entered");
-        if (!/^[a-zA-Z]+$/.test(key)) throw new OperationError("The key must consist only of letters");
+        if (!/^[a-zA-Z0-9]+$/.test(key)) throw new OperationError("The key must consist only of letters and numbers");
 
         for (let i = 0; i < input.length; i++) {
-            if (alphabet.indexOf(input[i]) >= 0) {
-                // Get the corresponding character of key for the current letter, accounting
-                // for chars not in alphabet
+            const currentChar = input[i];
+            const lowerChar = currentChar.toLowerCase();
+
+            if (alphabet.indexOf(lowerChar) >= 0) {
+                // Get the corresponding character of key for the current letter
                 chr = key[(i - fail) % key.length];
-                // Get the location in the vigenere square of the key char
                 keyIndex = alphabet.indexOf(chr);
-                // Get the location in the vigenere square of the message char
-                msgIndex = alphabet.indexOf(input[i]);
-                // Get the encoded letter by finding the sum of indexes modulo 26 and finding
-                // the letter corresponding to that
-                output += alphabet[(keyIndex + msgIndex) % 26];
-            } else if (alphabet.indexOf(input[i].toLowerCase()) >= 0) {
-                chr = key[(i - fail) % key.length].toLowerCase();
-                keyIndex = alphabet.indexOf(chr);
-                msgIndex = alphabet.indexOf(input[i].toLowerCase());
-                output += alphabet[(keyIndex + msgIndex) % 26].toUpperCase();
+                msgIndex = alphabet.indexOf(lowerChar);
+                const encodedChar = alphabet[(keyIndex + msgIndex) % alphabet.length];
+
+                // Preserve case for letters
+                output += currentChar === lowerChar ? encodedChar : encodedChar.toUpperCase();
             } else {
-                output += input[i];
+                output += currentChar; // Keep non-alphabetic characters as is
                 fail++;
             }
         }
@@ -101,7 +95,6 @@ class VigenèreEncode extends Operation {
     highlightReverse(pos, args) {
         return pos;
     }
-
 }
 
 export default VigenèreEncode;