src/index.css

 .chatui {
   display: flex;
   flex-flow: column wrap;
   justify-content: space-between;
   width: 100%;
   max-width: 867px;
   margin: 25px 10px;
   height: 600px;
   border: 2px solid #ddd;
   border-radius: 5px;
   box-shadow: 0 15px 15px -5px rgba(0, 0, 0, 0.2);
 }

 s .chatui-header {
   display: flex;
   justify-content: space-between;
   padding: 10px;
   border-bottom: 2px solid #ddd;
   background: #eee;
   color: #666;
 }

 .chatui-chat {
   flex: 1;
   overflow-y: auto;
   padding: 10px;
 }

 .chatui-chat::-webkit-scrollbar {
   width: 6px;
 }

 .chatui-chat::-webkit-scrollbar-track {
   background: #ddd;
 }

 .chatui-chat::-webkit-scrollbar-thumb {
   background: #bdbdbd;
 }

 .msg {
   display: flex;
   align-items: flex-end;
   margin-bottom: 10px;
 }

 .msg:last-of-type {
   margin: 0;
 }

 .msg-bubble {
   max-width: 450px;
   padding: 15px;
   border-radius: 15px;
   background: #ececec;
 }

 .left-msg .msg-bubble {
   border-bottom-left-radius: 0;
 }

 .error-msg .msg-bubble {
  border-bottom-left-radius: 0;
  color: #f15959;
}

.init-msg .msg-bubble {
  border-bottom-left-radius: 0;
}

 .right-msg {
   flex-direction: row-reverse;
 }

 .right-msg .msg-bubble {
   background: #579ffb;
   color: #fff;
   border-bottom-right-radius: 0;
 }

 .chatui-inputarea {
   display: flex;
   padding: 10px;
   border-top: 2px solid #ddd;
   background: #eee;
 }

 .chatui-inputarea * {
   padding: 10px;
   border: none;
   border-radius: 3px;
   font-size: 1em;
 }

 .chatui-input {
   flex: 1;
   background: #ddd;
 }

 .chatui-reset-btn {
   margin-left: 10px;
   background: #ececec;
   font-weight: bold;
   border-radius: 8px;
   width: 200px;
   cursor: pointer;
 }

 .chatui-reset-btn:hover {
  background: #dcdada;
}

 .chatui-send-btn {
  margin-left: 10px;
  background: #579ffb;
  color: #fff;
  font-weight: bold;
  cursor: pointer;
}

.chatui-send-btn:hover {
  background: #577bfb;
}

 .chatui-chat {
   background-color: #fcfcfe;
 }