static/css/style.css

/* screen configs */
* {
  box-sizing: border-box;
  padding: 0;
  margin: 0;
}

body {
  background-color: #f4f4f4;
  font-family: 'Roboto', sans-serif;
}

ul { list-style: none; } 

h1 {
  text-transform: uppercase;
  margin: 0 auto;
  padding: 20px;
  text-align: center;
  color: #3c3c3e;
}

/* chatbox */
.chat {
  max-width: 400px;
  min-height: 400px;
  background-color: #fff; 
  padding-right: 15px;
  padding-left: 15px;
  margin: 20px auto;
  border-radius: 1rem;
}

/* messages */
.messages {
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  height: 500px;
}

.message-list {
  overflow-y: scroll;
  max-height: 500px;
}

.message-item {
  padding: 20px;
  border-radius: 0.75rem;
  margin: 20px 0;
}

.message-item:last-child {
  margin-bottom: 0;
}

.item-primary {
  background-color: #f6f7f8;
  color: #3c3c3e;
}

.item-secondary {
  background-color: #5ccad7;
  color: #fff;
}

/* messages input */
.message-input {
  display: flex;
  padding: 20px 0;
}

.message-input input {
  width: 100%;
  padding: 10px;
  border-radius: 2rem;
  border: 1px solid #a5a5a5;
}

.message-input button {
  padding: 10px;
  margin-left: 10px;
  border-radius: 5px;
  border: none;
  cursor: pointer;
}