* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}
body {
  display: flex;
  min-height: 100vh;
  justify-content: center;
  align-items: center;
  flex-direction: column;
  background-color: #333;
  font-family: Arial, Helvetica, sans-serif;
}

h1 {
  color: #fff;
  margin-bottom: 20px;
}
.keys {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 10px;
}
.key {
  width: 80px;
  height: 80px;
  border: 2px solid #fff;
  color: #fff;
  display: flex;
  justify-content: center;
  align-items: center;
  font-size: 30px;
  font-weight: bold;
}
.key.active {
  border: 2px solid #ff0;
  color: #ff0;
}

.composer {
  width: 260px;
  margin-top: 20px;
}
.composer #input {
  width: 100%;
  outline: none;
  font-size: 17px;
  padding: 10px 15px;
}
.composer button {
  width: 100%;
  height: 40px;
  background: none;
  border: 2px solid #fff;
  color: #fff;
  font-size: 16px;
  margin-top: 10px;
  cursor: pointer;
}
.composer button:hover {
  background-color: rgba(0, 0, 0, 0.2);
}

footer {
  margin-top: 20px;
  color: #fff;
  font-size: 13px;
}
footer a {
  text-decoration: none;
  color: #fff;
  font-size: 13px;
}