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

body, html {
  height: 100%;
  font-family: 'Segoe UI', sans-serif;
}

#app {
  display: flex;
  height: 100vh;
}

#sidebar {
  width: 200px;
  background: #2f3136;
  color: #fff;
  padding: 20px;
}

#sidebar h2 {
  margin-bottom: 20px;
  font-size: 20px;
}

#channel-list {
  list-style: none;
}

.channel {
  padding: 10px;
  border-radius: 5px;
  cursor: pointer;
  color: #b9bbbe;
}

.channel:hover, .channel.active {
  background-color: #40444b;
  color: white;
}

#chat {
  flex: 1;
  display: flex;
  flex-direction: column;
  background: #36393f;
  color: white;
}

#chat-header {
  padding: 10px;
  background: #2f3136;
  border-bottom: 1px solid #202225;
  display: flex;
  justify-content: space-between;
  align-items: center;
}

#messages {
  flex: 1;
  padding: 15px;
  overflow-y: auto;
}

#chat-form {
  display: flex;
  padding: 10px;
  background: #40444b;
}

#message-input {
  flex: 1;
  padding: 10px;
  border: none;
  border-radius: 5px;
  outline: none;
}

#chat-form button {
  padding: 10px 15px;
  margin-left: 10px;
  background: #7289da;
  color: white;
  border: none;
  border-radius: 5px;
  cursor: pointer;
}

#username-screen {
  position: absolute;
  top: 0;
  left: 0;
  background: rgba(0,0,0,0.85);
  width: 100%;
  height: 100%;
  display: flex;
  align-items: center;
  justify-content: center;
}

#username-form {
  background: #2f3136;
  padding: 30px;
  border-radius: 10px;
  text-align: center;
}

#username-form input {
  width: 100%;
  margin-top: 10px;
  padding: 10px;
  border: none;
  border-radius: 5px;
}

#username-form button {
  margin-top: 10px;
  padding: 10px;
  background: #7289da;
  color: white;
  border: none;
  border-radius: 5px;
  cursor: pointer;
}