style.css

:root {
  --keyBoard-bg: #000;
  --keyboard-shadow: rgba(0, 0, 0, 0.5);
  --keys-bg: rgba(255, 255, 255, 0.2);
  --key-active: rgba(255, 255, 255, 0.12);
  --font-color: #fff;
  --key-active-before: rgba(238, 238, 238, 0.4);
  --input-focus: rgb(158, 158, 158);
}

* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
  font-family: 'Times New Roman', Times, serif;
}

body {
  padding: 20px;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 30px;
}
h1 {
  text-align: center;
}

textarea {
  width: 50%;
  height: 200px;
  font-size: 22px;
  letter-spacing: 2px;
  padding: 10px;
  outline: 2px solid black;
}

textarea:focus {
  border: 4px solid var(--input-focus);
}

.keyboard {
  position: fixed;
  left: 0;
  bottom: 0;
  width: 100%;
  padding: 5px 0;
  background: var(--keyBoard-bg);
  box-shadow: 0 0 50px var(--keyboard-shadow);
  user-select: none;
  transition: bottom 0.4s;
}

.keyboard--hidden {
  bottom: -100%;
}

.keyboard__keys {
  text-align: center;
}

.keyboard__key {
  height: 45px;
  width: 6%;
  max-width: 90px;
  margin: 3px;
  border-radius: 4px;
  border: none;
  background: var(--keys-bg);
  color: var(--font-color);
  font-size: 1.25rem;
  outline: none;
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  vertical-align: top;
  padding: 0;
  -webkit-tap-highlight-color: transparent;
  position: relative;
}

.keyboard__key:active {
  background: var(--key-active);
}

.keyboard__key--wide {
  width: 12%;
}

.keyboard__key--extra-wide {
  width: 36%;
  max-width: 500px;
}

.keyboard__key--activatable::after {
  content: '';
  top: 10px;
  right: 10px;
  position: absolute;
  width: 8px;
  height: 8px;
  background: var(--key-active-before);
  border-radius: 50%;
}

.keyboard__key--active::after {
  background: var(--font-color);
}

.keyboard__key--dark {
  background: var(--keys-bg);
}