:root {
  --color: antiquewhite;
  --body: aliceblue;
  --start: #27ae60;
  --stop: #c0392b;
  --reset: #7f8c8d;
  --text: #2c3e50;
}

* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

body {
  gap: 20px;
  display: flex;
  padding: 100px;
  align-items: center;
  flex-direction: column;
  justify-content: center;

  color: var(--text);
  background: var(--body);

  font-size: 20px;
  font-family: "Franklin Gothic Medium", "Arial Narrow", Arial, sans-serif;
}

header {
  gap: 20px;
  display: flex;
  align-items: center;
  flex-direction: column;
  justify-content: center;
}

.header-title {
  font-size: 36px;
}

.header-time {
  font-size: 72px;
}

main {
  gap: 10px;
  display: flex;
  align-items: center;
}

.btn {
  border: none;
  cursor: pointer;
  font-size: 18px;
  padding: 10px 20px;
  border-radius: 4px;
  color: var(--color);
  text-transform: uppercase;
  transition: opacity 0.3s ease-in-out;
}

.start {
  background: var(--start);
}

.stop {
  background: var(--stop);
}

.reset {
  background: var(--reset);
}