diff --git a/core/migrate.js b/core/migrate.js
index a2948e0..8c57b21 100644
--- a/core/migrate.js
+++ b/core/migrate.js
@@ -1,12 +1,12 @@
 const upOrDown = (fromVersion, toVersion) => {
   const fromNumbers = fromVersion.split(".").map(el => Number(el));
   const toNumbers = toVersion.split(".").map(el => Number(el));
-  for (let i = 0; i < fromNumbers.length; i++) {
-    if (fromNumbers[i] < toNumbers[i]) {
-      return "up";
-    }
-    if (fromNumbers[i] > toNumbers[i]) {
-      return "down";
+  const longestLength = Math.max(fromNumbers.length, toNumbers.length);
+  for (let i = 0; i < longestLength; i++) {
+    if (!fromNumbers[i]) fromNumbers[i] = 0;
+    if (!toNumbers[i]) toNumbers[i] = 0;
+    if (fromNumbers[i] != toNumbers[i]) {
+      return (fromNumbers[i] < toNumbers[i]) ? "up" : "down";
     }
   }
   return "same";
diff --git a/core/utils.js b/core/utils.js
index 0dda340..a77c951 100644
--- a/core/utils.js
+++ b/core/utils.js
@@ -7,25 +7,18 @@ const sleep = (ms = 0) => {
 
 const roll = (critRate, _player = null) => {
     dice = Math.random() * 100;
-    if (!_player) {
-        return dice < critRate;
-    } else {
+    if(_player && _player.rollCounter >= 0) {
         _player.rollCounter++;
-        if (_player.rollCounter == 100) {
-            _player.rollCounter = 0;
-            return true; // 100% guarantee rate
-        }
         let rateUp = 0;
         if (_player.rollCounter >= 80) {
-            rateUp = _player.rollCounter / 10;
+            rateUp = (_player.rollCounter == 100)? 100 : _player.rollCounter / 10;
         }
-        let catchIt = dice < (critRate + rateUp);
-        if (catchIt) {
-            // reset roll counter
+        if (dice < critRate + rateUp) {
             _player.rollCounter = 0;
+            return true;
         }
-        return catchIt;
     }
+    return dice < critRate;
 }
 
 module.exports = {