vue3/style.css

html,
body {
  width: 100vw;
  height: 100vh;
  background: #00a08a;
  color: whitesmoke;
}

#app {
  display: grid;
  place-items: center;
  height: 100vh;
}

#btn {
  scale: 200%;
  border-radius: 15px;
  outline: none;
  border: 1px solid blue;
  transition: all 0.2s;
}

#btn:hover {
  background: #87ceeb;
  color: whitesmoke;
}

#btn:active {
  scale: 185%;
}

label,
input[type="checkbox"] {
  display: inline-block;
  vertical-align: middle;
}

.checkBox {
  display: block;
  cursor: pointer;
  width: 30px;
  height: 30px;
  border: 3px solid rgba(255, 255, 255, 0);
  border-radius: 10px;
  position: relative;
  overflow: hidden;
  box-shadow: 0px 0px 0px 2px #fff;
}

.checkBox div {
  width: 60px;
  height: 60px;
  background-color: #fff;
  top: -52px;
  left: -52px;
  position: absolute;
  transform: rotateZ(45deg);
  z-index: 100;
}

.checkBox input[type="checkbox"]:checked + div {
  left: -10px;
  top: -10px;
}

.checkBox input[type="checkbox"] {
  position: absolute;
  left: 50px;
  visibility: hidden;
  vertical-align: middle;
}

.transition {
  transition: 300ms ease;
}

.inputData {
  width: fit-content;
  height: 40px;
  display: flex;
  align-items: center;
  justify-content: center;
  background-color: rgba(45, 45, 45, 0.9);
  padding: 0 15px;
  border-radius: 10px;
  border: 2px solid rgb(63, 63, 63);
}

.inputData:focus-within {
  border: 2px solid rgb(110, 110, 110);
}

#messageInput {
  width: 200px;
  height: 100%;
  background-color: transparent;
  outline: none;
  border: none;
  padding-left: 10px;
  color: white;
}
#messageInput:focus ~ #sendButton svg path,
#messageInput:valid ~ #sendButton svg path {
  fill: #3c3c3c;
  stroke: white;
}

#sendButton {
  width: fit-content;
  height: 100%;
  background-color: transparent;
  outline: none;
  border: none;
  cursor: pointer;
  transition: all 0.3s;
}
#sendButton svg {
  height: 18px;
  transition: all 0.3s;
}
#sendButton svg path {
  transition: all 0.3s;
}
#sendButton:hover svg path {
  fill: #3c3c3c;
  stroke: white;
  scale: 110%;
}

#sendButton:active svg path {
  scale: 90%;
}