diff --git a/public/parent.html b/public/parent.html
index d9865c4..7235361 100644
--- a/public/parent.html
+++ b/public/parent.html
@@ -16,6 +16,11 @@
         }, {
           type: 'text',
           title: 'Phone'
+        }, {
+          type: 'radio',
+          title: 'Test',
+          optTexts: ['Option 1', 'Option 2', 'Option 3'],
+          optValues: ['Option 1', 'Option 2', 'Option 3']
         }]
       };
       window.onload = () => {        
diff --git a/src/App.vue b/src/App.vue
index 9573d82..9fa349b 100644
--- a/src/App.vue
+++ b/src/App.vue
@@ -1,7 +1,19 @@
 <script>
-  // import Item from './item.js';
-  function isValid({type, title, optTexts, optValues = null}) {
-    if (!title || !["text", "radio", "checkbox", "scale"].includes(type)) {
+  /*
+  * Specification of item data structure:
+  * {
+  *  type: string, // 'text', 'radio', 'checkbox', 'scale'
+  *  title: string,
+  *  optTexts: string[], // only for 'radio', 'checkbox', 'scale'
+  *  optValues: string[], // only for 'radio', 'checkbox', 'scale'
+  *  required: boolean, // optional, whether the user must answer the question, default is true
+  *  answer: string, // user's answer, appended after user submits
+  *  refilled: boolean, // whether the user refilled the answer, appended after user submits
+  * }
+  */
+  const ITEM_TYPES = ['text', 'radio', 'checkbox', 'scale'];
+  function isValidItem({type, title, optTexts, optValues = null}) {
+    if (!title || !ITEM_TYPES.includes(type)) {
       return false;
     }
     if (type === "text") {
@@ -19,74 +31,162 @@
         title: undefined,
         items: [],
         currentIdx: undefined,
-        currentAnswer: undefined
+        currentItem: undefined,
+        currentAnswer: undefined,
+        currentAnswerValue: undefined,
+        currentRefilled: false,
+        timestamp: undefined,
+        settings: {
+          allowBack: true,
+        },
       }
     },
     created() {
       window.addEventListener('message', (event) => {
         const data = event.data;
         if (event.source === window.parent && data && data.type === 'iframe') {
-          this.items = data.items;
+          this.settings = Object.assign(this.settings, data.settings);
+          this.items = structuredClone(data.items);
           this.title = data.title;
-          this.currentIdx = 0;
-          if (!this.items.every(item => isValid(item))) {
+          if (!this.items.every(item => isValidItem(item))) {
             throw new Error('Invalid item');
           }
+          
+          this.currentIdx = 0;
+          this.currentItem = this.items[this.currentIdx];
+          this.timestamp = new Date().getTime();
         }
       });
     },
-    methods: {
-      getDisplayTitle() {
-        return `${this.currentIdx + 1}. ${this.items[this.currentIdx].title}`;
-      },
-      clickNext() {
-        if (this.items[this.currentIdx].type === 'text') {
-          this.items[this.currentIdx].answer = this.currentAnswer;
-        }
-        this.currentIdx = (this.currentIdx + 1) % this.items.length;
-        if (this.items[this.currentIdx].answer) {
-          this.currentAnswer = this.items[this.currentIdx].answer;
-        } else {
-          this.currentAnswer = '';
-        }
-      },
+    computed: {
       isReady() {
         return this.items && this.title;
+      },
+      displayTitle() {
+        return `${this.currentIdx + 1}. ${this.items[this.currentIdx].title}`;
+      },
+      nextButtonText() {
+        return this.currentIdx === this.items.length - 1 ? 'Submit' : 'Next';
+      },
+      nextButtonStatus() {
+        return this.currentIdx === this.items.length - 1 ? 'submit' : '';
+      },
+      backButtonStatus() {
+        return this.currentIdx === 0 ? 'disabled' : '';
+      }
+    },
+    methods: {
+      clickNext() {
+        const item = this.items[this.currentIdx];
+        item.answer = this.currentAnswer;
+        item.refilled = this.currentRefilled;
+        item.responseTime = new Date().getTime() - this.timestamp;
+
+        if (this.currentIdx === this.items.length - 1) {
+          this.submit();
+        } else {
+          this.currentIdx++;
+          this.currentAnswer = null;
+          this.currentItem = this.items[this.currentIdx];
+          this.currentRefilled = (this.currentItem.answer !== undefined);
+          this.timestamp = new Date().getTime();
+        }
+      },
+      clickBack() {
+        if (this.currentIdx > 0) {
+          this.currentIdx--;
+          this.currentAnswer = this.items[this.currentIdx].answer;
+          this.currentItem = this.items[this.currentIdx];
+          this.currentRefilled = (this.currentItem.answer !== undefined);
+          this.timestamp = new Date().getTime();
+        }
+      },
+      submit() {
+        const results = this.items.map((item, index) => ({
+          index: index,
+          title: item.title,
+          answer: item.answer,
+          refilled: item.refilled,
+          responseTime: item.responseTime,
+        }));
+        const elem = document.createElement('a');
+        elem.href = 'data:text/json;charset=utf-8,' + encodeURIComponent(JSON.stringify(results));
+        elem.download = 'results.json';
+        elem.click();
       }
     }
   }
 </script>
 
 <template>
-  <div v-if="isReady()">
-    <template v-if="items[currentIdx].type === 'text'">
-      <span class="itemTitle">{{ getDisplayTitle() }}</span>
-      <input type="text" v-model="currentAnswer">
+  <div class="container" v-if="isReady">
+    <span class="display-title">{{ displayTitle }}</span>
+    <template v-if="currentItem.type === 'text'">
+      <div class="item text">
+        <input type="text" v-model="currentAnswer">
+      </div>
     </template>
-    <button @click="clickNext">Next</button>
+    <template v-else-if="currentItem.type === 'radio'">
+      <div class="item radio" v-for="(optText, index) in currentItem.optTexts" :key="index">
+        <input type="radio" :id="index" :value="currentItem.optValues[index]" v-model="currentAnswer">
+        <label :for="index">{{ optText }}</label>
+      </div>
+    </template>
+    
+    <button
+      v-if="settings.allowBack"
+      @click="clickBack"
+      :class="backButtonStatus">Back</button>
+    <button @click="clickNext" :class="nextButtonStatus">{{ nextButtonText }}</button>
   </div>
 </template>
 
 <style scoped>
+  .container {
+    text-align: left;
+    width: 100%;
+  }
   button {
-    background-color: #4CAF50;
+    background-color: #008CBA;
     border: none;
     color: white;
-    padding: 15px 15px;
+    padding: 10px 20px;
     text-align: center;
     text-decoration: none;
-    border-radius: 4px;
+    border-radius: 5px;
     display: inline-block;
-    font-size: 16px;
+    font-size: 18px;
+    margin-right: 20px;
+  }
+  button.submit {
+    background-color: #4CAF50;
+  }
+  button.disabled {
+    background-color: #cccccc;
   }
   input[type=text] {
     width: 100%;
-    padding: 12px 20px;
+    padding: 12px 18px;
     margin: 8px 20px 20px 0px;
     display: inline-block;
     box-sizing: border-box;
+    border: 2px solid #ccc;
+    border-radius: 4px;
+    font-size: 16px;
   }
-  .itemTitle {
+  input[type=radio] {
+    margin-bottom: 4px;
+    margin-right: 10px;
+    text-align: left;
+  }
+  label {
+    font-size: 16px;
+  }
+  .item {
+    margin-bottom: 20px;
+    width: 100%;
+  }
+  .display-title {
     font-size: 20px;
     font-weight: bold;
   }