diff --git a/conjugation/drill.html b/conjugation/drill.html
index 51b8f58..63ce783 100644
--- a/conjugation/drill.html
+++ b/conjugation/drill.html
@@ -15,6 +15,36 @@
         <span>Number of Questions</span>
         <input id="numQuestions" value="10">
       </div>
+
+      <div>
+        <h2>Conjugation types</h2>
+        <ul>
+          <li><label><input type="checkbox" id="polite" checked="true"> Polite</label></li>
+          <li><label><input type="checkbox" id="negative" checked="true"> Negative</label></li>
+          <li><label><input type="checkbox" id="te-form"> て form</label></li>
+<!--
+          <li><label><input type="checkbox" id="potential"> Potential</label></li>
+          <li><label><input type="checkbox" id="imperative"> Imperative</label></li>
+          <li><label><input type="checkbox" id="passive"> Passive</label></li>
+          <li><label><input type="checkbox" id="causative"> Causative</label></li>
+-->
+        </ul>
+      </div>
+
+      <div>
+        <h2>Verb classes</h2>
+        <ul>
+          <li><label><input type="checkbox" id="godan" checked="true"> Godan verbs</label></li>
+          <li><label><input type="checkbox" id="godan-mu" checked="true"> Godan verbs with a mu ending</label></li>
+          <li><label><input type="checkbox" id="godan-ru" checked="true"> Godan verbs with a ru ending</label></li>
+          <li><label><input type="checkbox" id="godan-u" checked="true"> Godan verbs with an u ending</label></li>
+          <li><label><input type="checkbox" id="ichidan" checked="true"> Ichidan verbs</label></li>
+          <li><label><input type="checkbox" id="kuru" checked="true"> Kuru verb</label></li>
+          <li><label><input type="checkbox" id="iku" checked="true"> Iku verb</label></li>
+          <li><label><input type="checkbox" id="suru" checked="true"> Suru verbs</label></li>
+        </ul>
+      </div>
+
       <button id="go">Go</button>
 
       <div><small>
diff --git a/conjugation/drill.js b/conjugation/drill.js
index afc164e..549142f 100644
--- a/conjugation/drill.js
+++ b/conjugation/drill.js
@@ -577,10 +577,10 @@ var verb_relative_form = {
     "past": "present",
     "polite": "plain",
     "te-form": "plain",
-    "potential": "plain",
-    "imperative": "plain",
-    "causative": "plain",
-    "passive": "plain",
+//    "potential": "plain",
+//    "imperative": "plain",
+//    "causative": "plain",
+//    "passive": "plain",
   },
 
   "negative": {
@@ -589,10 +589,10 @@ var verb_relative_form = {
     "past negative": "present",
     "polite negative": "plain",
     "te-form negative": "plain",
-    "potential negative": "plain",
-    "imperative negative": "plain",
-    "causative negative": "plain",
-    "passive negative": "plain",
+//    "potential negative": "plain",
+//    "imperative negative": "plain",
+//    "causative negative": "plain",
+//    "passive negative": "plain",
   },
 
   "past" : {
@@ -649,71 +649,71 @@ var verb_relative_form = {
     "negative" : "て",
   },
 
-  "potential" : {
-
-    "plain" : "potential",
-    "potential negative" : "affirmative",
-  },
-
-  "potential negative" : {
-
-    "potential" : "negative",
-    "negative" : "potential",
-  },
-
-  "imperative" : {
-
-    "plain" : "imperative",
-    "imperative negative" : "affirmative",
-  },
-
-  "imperative negative" : {
-
-    "imperative" : "negative",
-    "negative" : "imperative",
-  },
-
-  "causative" : {
-
-    "plain" : "causative",
-    "causative negative" : "affirmative",
-    "causative passive" : "active",
-  },
-
-  "causative negative" : {
-
-    "causative" : "negative",
-    "negative" : "causative",
-    "causative passive negative" : "active",
-  },
-
-  "passive" : {
-
-    "plain" : "passive",
-    "passive negative" : "affirmative",
-    "causative passive" : "non-causative",
-  },
-
-  "passive negative" : {
-
-    "passive" : "negative",
-    "negative" : "passive",
-    "causative passive negative" : "non-causative"
-  },
-
-  "causative passive" : {
-
-    "causative" : "passive",
-    "passive" : "causative",
-    "causative passive negative" : "affirmative",
-  },
-
-  "causative passive negative" : {
-
-    "causative negative" : "passive",
-    "passive negative" : "causative",
-    "causative passive" : "negative",
-  },
+//  "potential" : {
+//
+//    "plain" : "potential",
+//    "potential negative" : "affirmative",
+//  },
+//
+//  "potential negative" : {
+//
+//    "potential" : "negative",
+//    "negative" : "potential",
+//  },
+//
+//  "imperative" : {
+//
+//    "plain" : "imperative",
+//    "imperative negative" : "affirmative",
+//  },
+//
+//  "imperative negative" : {
+//
+//    "imperative" : "negative",
+//    "negative" : "imperative",
+//  },
+//
+//  "causative" : {
+//
+//    "plain" : "causative",
+//    "causative negative" : "affirmative",
+//    "causative passive" : "active",
+//  },
+//
+//  "causative negative" : {
+//
+//    "causative" : "negative",
+//    "negative" : "causative",
+//    "causative passive negative" : "active",
+//  },
+//
+//  "passive" : {
+//
+//    "plain" : "passive",
+//    "passive negative" : "affirmative",
+//    "causative passive" : "non-causative",
+//  },
+//
+//  "passive negative" : {
+//
+//    "passive" : "negative",
+//    "negative" : "passive",
+//    "causative passive negative" : "non-causative"
+//  },
+//
+//  "causative passive" : {
+//
+//    "causative" : "passive",
+//    "passive" : "causative",
+//    "causative passive negative" : "affirmative",
+//  },
+//
+//  "causative passive negative" : {
+//
+//    "causative negative" : "passive",
+//    "passive negative" : "causative",
+//    "causative passive" : "negative",
+//  },
 };
 
 function wordWithFurigana(word) {