style.css

* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
  font-family: "Space Mono", Courier, monospace;
  line-height: 1.8em;
}

:root {
  --pageBg: #1a1c22;
  --containerBg: #222125;
  --complementaryColor: #ffdf00;
  --fontColor: #f7f7f7;
  --containerBorderColor: #28272b;
  --containerRadius: 5px;
  --responsibleFontSize: clamp(1rem, 2vw, 1.3rem);
  --scrollBarBtnColor: #3b3a3f;
  --errorFontColor: #9e0000;
}

body {
  /* from bgjar.com */
  min-height: 100vh;
  overflow: hidden;
  background: var(--pageBg);
  color: var(--fontColor);
}

header {
  height: 20vh;
  display: flex;
  justify-content: center;
  align-items: center;
}

header h1 {
  position: relative;
  padding: 2%;
  color: var(--complementaryColor);
  font-size: clamp(30px, 3vw, 50px);
  line-height: 3rem;
  text-align: center;
}

main {
  width: 75vw;
  height: 60vh;
  overflow-y: scroll;
  background: var(--containerBg);
  padding: 2%;
  margin: 0 auto 10vh auto;
  border: 3px solid var(--containerBorderColor);
  border-radius: var(--containerRadius);
  font-size: var(--responsibleFontSize);
}

.line {
  margin-bottom: 2% 0;
}

.line span:nth-child(1) {
  font-weight: 700;
}

.marked {
  color: var(--complementaryColor);
  font-weight: 700;
  animation: flashing 1s infinite linear;
}

.line.has-answer {
  display: flex;
}

.line.error {
  color: var(--errorFontColor);
}

.answer {
  min-width: 50%;
  background: transparent;
  border: none;
  outline: none;
  caret-color: var(--fontColor);
  font-size: var(--responsibleFontSize);
  color: var(--fontColor);
  word-break: break-all;
  cursor: text;
  caret-color: var(--complementaryColor);
}

/* scroll bar */
main::-webkit-scrollbar {
  background: var(--containerBorderColor);
}

main::-webkit-scrollbar-thumb {
  background-color: var(--scrollBarBtnColor);
  border-left: 3px solid var(--containerBorderColor);
  border-radius: 15px;
}

@keyframes flashing {
  0% {
    opacity: 1;
  }
  50% {
    opacity: 0;
  }
  100% {
    opacity: 1;
  }
}