styles.css

*,
*::before,
*::after {
  box-sizing: border-box;
}

body {
  margin: 0;
}

.chat {
  position: absolute;
  left: 0;
  top: 0;
  width: 100%;
  height: 100%;
  display: flex;
  flex-flow: column;
  justify-content: space-between;
  text-shadow: 0 0.25vh 0vh #000;
  overflow-x: hidden;
  user-select: none;
}

.chat.hidden {
  visibility: hidden;
}

.chat__messages-container {
  position: absolute;
  max-height: 100%;
  bottom: 0;
  left: 0;
  width: 100%;
}

.chat__messages {
  position: relative;
  height: 80%;
  overflow-y: scroll;
}

.chat__messages::-webkit-scrollbar {
  width: 0.1vh;
}

.chat__messages::-webkit-scrollbar-track,
.chat__messages::-webkit-scrollbar-thumb {
  background-color: transparent;
}

.chat__message {
  word-break: break-all;
  font-size: 5vh;
  line-height: 130%;
  font-family: sans-serif;
  font-weight: 700;
  color: #ffffff;
}

.chat__message:last-child {
  margin-bottom: 0;
}

.chat__input-block {
  position: relative;
}

.chat__input-block.hidden {
  display: none;
}

.chat__input-label {
  position: absolute;
  top: 50%;
  left: 0;
  padding: 1vh 2vh;
  margin-left: 2vh;
  transform: translateY(-50%);
  background-color: rgba(0, 0, 0, 0.25);
  border: 1px solid rgba(0, 0, 0, 0.25);
  border-radius: 1vh;
  text-transform: uppercase;
  font-size: 3vh;
  font-family: sans-serif;
  font-weight: 700;
  text-align: center;
  color: #ffffff;
}

.chat__input {
  padding: 2vh;
  width: 100%;
  background-color: rgba(0, 0, 0, 0.25);
  border: 1px solid rgba(0, 0, 0, 0.25);
  color: #ffffff;
  font-size: 4vh;
  text-shadow: 0 0.1vh 0.2vh rgba(0, 0, 0, 0.5);
  font-family: sans-serif;
  font-weight: 700;
  border-radius: 1vh;
}

.chat__input:focus {
  outline: none;
}