* {
  border: 0;
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}
:root {
  --hue: 0;
  --sat: 0%;
  --bg: hsl(var(--hue), var(--sat), 90%);
  --fg: hsl(var(--hue), var(--sat), 10%);
  --trans-dur: 0.3s;
  font-size: calc(16px + (24 - 16) * (100vw - 320px) / (2560 - 320));
}
body,
button {
  color: var(--fg);
  font: 1em/1.5 -apple-system, BlinkMacSystemFont, "Helvetica Neue", Helvetica, sans-serif;
}
body {
  background-color: var(--bg);
  background-image: linear-gradient(-45deg, hsla(var(--hue), var(--sat), 0%, 0), hsla(var(--hue), var(--sat), 0%, 0.3));
  display: flex;
  height: 100vh;
  transition: background-color var(--trans-dur), color var(--trans-dur);
}
.keyboard,
.keyboard:before,
.keyboard:after {
  transition: background-color var(--trans-dur), box-shadow var(--trans-dur);
}
.keyboard,
.keyboard__key-lines {
  display: flex;
}
.keyboard {
  background-color: hsl(var(--hue), var(--sat), 80%);
  background-image: linear-gradient(90deg, hsla(var(--hue), var(--sat), 10%, 0.4), hsla(var(--hue), var(--sat), 10%, 0));
  border-radius: 0.75em;
  box-shadow: -0.5em -0.5em 0.75em hsla(0, 0%, 0%, 0.6), 0 0 0 1px hsl(var(--hue), var(--sat), 67%) inset;
  align-items: center;
  margin: auto;
  padding: 0.375em;
  position: relative;
  width: 18.5em;
  height: 6.5em;
}
.keyboard:before,
.keyboard:after {
  background-color: hsl(var(--hue), var(--sat), 90%);
  content: "";
  display: block;
  position: absolute;
  bottom: 100%;
}
.keyboard:before {
  box-shadow: -0.5em -0.5em 0.75em hsla(0, 0%, 0%, 0.6), 0.25em 0 0.25em hsla(var(--hue), var(--sat), 10%, 0.2) inset, 0.25em -1.25em 0.5em hsla(var(--hue), var(--sat), 10%, 0.5) inset;
  left: calc(50% - 0.5em);
  width: 1em;
  height: 40em;
}
.keyboard:after {
  border-radius: 0.25em 0.25em 0 0;
  box-shadow: 0.375em -0.25em 0.5em hsla(var(--hue), var(--sat), 10%, 0.5) inset;
  left: calc(50% - 0.75em);
  width: 1.5em;
  height: 1.25em;
}
.keyboard__cmd {
  display: block;
  width: 1em;
  height: 1em;
}
.keyboard__key {
  background-color: hsl(var(--hue), var(--sat), 95%);
  border-radius: 0.5em;
  box-shadow: -0.4em -0.25em 0.25em hsla(0, 0%, 0%, 0.25), 0 0 0 0.1em hsla(0, 0%, 0%, 0.3), 0.04em 0.04em 0.04em hsla(0, 0%, 0%, 0.4) inset, -0.1em -0.1em 0.04em hsla(0, 0%, 100%, 0.8) inset;
  color: hsl(var(--hue), var(--sat), 50%);
  margin: 0 0.375em;
  outline: transparent;
  padding: 0.75em;
  position: relative;
  width: 5em;
  height: 5em;
  transition: background-color var(--trans-dur), box-shadow 0.15s, color var(--trans-dur);
  -webkit-appearance: none;
  appearance: none;
  -webkit-user-select: none;
  -moz-user-select: none;
  user-select: none;
  -webkit-tap-highlight-color: transparent;
}
.keyboard__key--meta {
  width: 5.5em;
}
.keyboard__key:active,
.keyboard__key.active {
  box-shadow: 0 0 0.2em hsla(0, 0%, 0%, 0.2), 0 0 0 0.1em hsla(0, 0%, 0%, 0.4), 0 -0.05em 0 hsla(0, 0%, 0%, 0.6) inset, -0.05em -0.15em 0.05em hsla(0, 0%, 100%, 0.8) inset;
}
.keyboard__key-line {
  font-size: 2em;
  line-height: 1;
}
.keyboard__key-line--small {
  font-size: 0.875em;
}
.keyboard__key-line--tr {
  margin: 0 0 auto auto;
}
.keyboard__key-line--br {
  margin: auto 0 0 auto;
}
.keyboard__key-lines {
  display: flex;
  justify-content: center;
  align-items: center;
  flex-direction: column;
  width: 100%;
  height: 100%;
  transition: transform 0.15s;
}
.keyboard__key:active .keyboard__key-lines,
.keyboard__key.active .keyboard__key-lines {
  transform: translateY(-1px);
}
.keyboard__key:before {
  box-shadow: 0 0 0 0.5em hsla(223, 90%, 50%, 0);
  border-radius: 0.5em;
  content: "";
  display: block;
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  transition: box-shadow var(--trans-dur);
}
.keyboard__key:focus-visible:before {
  box-shadow: 0 0 0 0.5em hsla(223, 90%, 50%, 0.5);
}

/* Dark theme */
@media (prefers-color-scheme: dark) {
  :root {
    --bg: hsl(var(--hue), var(--sat), 20%);
    --fg: hsl(var(--hue), var(--sat), 90%);
  }
  .keyboard__key {
    background-color: hsl(var(--hue), var(--sat), 15%);
    box-shadow: -0.4em -0.25em 0.25em hsla(0, 0%, 0%, 0.25), 0 0 0 0.1em hsla(0, 0%, 0%, 0.3), 0.04em 0.04em 0.04em hsla(0, 0%, 0%, 0.4) inset, -0.1em -0.1em 0.04em hsla(0, 0%, 100%, 0.05) inset;
    color: hsl(var(--hue), var(--sat), 90%);
  }
  .keyboard__key:active,
  .keyboard__key.active {
    box-shadow: 0 0 0.2em hsla(0, 0%, 0%, 0.2), 0 0 0 0.1em hsla(0, 0%, 0%, 0.4), 0 -0.05em 0 hsla(0, 0%, 0%, 0.4) inset, -0.05em -0.15em 0.05em hsla(0, 0%, 100%, 0.05) inset;
  }
}