html {
   font-size: 10px;
   background: black;
}

body, html {
   margin: 0;
   padding: 0;
   font-family: sans-serif;
}

.keys {
   display: flex;
   flex: 1;
   min-height: 85vh;
   align-items: center;
   justify-content: center;
}

.key {
   border: .4rem solid yellow;
   border-radius: .5rem;
   margin: 1rem;
   font-size: 1.5rem;
   padding: 1rem .5rem;
   transition: all .05s;
   width: 10rem;
   text-align: center;
   color: white;
   background: rgba(0, 0, 0, 0.5);
   text-shadow: 0 0 .5rem black;
}

kbd {
   display: block;
   font-size: 4rem;
}

.sound {
   font-size: 1.2rem;
   text-transform: uppercase;
   color: yellow;
}

.playing {
   transform: scale(1.2);
   border-color: yellow;
   box-shadow: 0 0 1rem yellow;
}

.info-box {
   display: flex;
   flex: 1;
   min-height: 15vh;
   font-size: 2rem;
   align-items: center;
   justify-content: center;
   background: rgba(0, 0, 0, 1);
   color: yellow;
}