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

:root {
  --bg-clr: #d9dae3;
  --white: #fff;
  --grey: #eee;
  --light-grey: #fafafa;
  --dark-grey: #aaa;
  --primary-clr: #00e5b1;
  --secondary-clr: #fdc886;
  --text-clr: #333;
}

html {
  font-size: 10px;
}

body {
  font-family: 'Montserrat', sans-serif;
  color: var(--text-clr);
  width: 100%;
  height: 100vh;
  display: flex;
  justify-content: center;
  align-items: center;
  background: var(--bg-clr);
}

.container {
  max-width: 90rem;
  margin: 0 auto;
  padding: 4rem;
  background: var(--white);
  border-radius: 2rem;
  box-shadow: 0 1rem 4rem 0 rgba(0, 0, 0, 0.1);
}

.container > * {
  margin-bottom: 2rem;
}

.header h3 {
  font-size: 2rem;
  text-align: center;
}

.result {
  display: flex;
  justify-content: center;
  align-items: center;
  position: relative;
  height: 20rem;
}

.result h1 {
  font-size: 5rem;
  color: var(--dark-grey);
}

.input-group {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 2rem;
  margin-bottom: 2rem;
}

.input-wrapper {
  display: flex;
  flex-direction: column;
}

.input-wrapper label {
  font-size: 1.5rem;
  color: var(--dark-grey);
  line-height: 3rem;
}

.input-wrapper input {
  height: 4rem;
  font-size: 1.5rem;
  line-height: 3rem;
  border: 1px solid var(--grey);
  border-radius: 1rem;
  background: var(--light-grey);
  outline-style: none;
  padding: 0 1rem;
}

.button-group {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 2rem;
}

.button-group button {
  width: 100%;
  height: 4rem;
  font-size: 1.5rem;
  border-radius: 1rem;
  border: none;
  display: flex;
  justify-content: center;
  align-items: center;
  gap: 0.5rem;
  cursor: pointer;
  transition: 0.25s ease;
}

.button-group button span {
  font-size: 1.7rem;
}

.button-group button:active {
  transform: scale(0.9);
}

#start-stop {
  border: 2px solid var(--primary-clr);
  background: none;
}

#instantly {
  background: var(--primary-clr);
}

.result h1.active {
  font-size: 15rem;
  color: var(--text-clr);
}