:root {
  /** Colors **/
  --Strong-cyan: hsl(172, 67%, 45%);
  --Very-dark-cyan: hsl(183, 100%, 15%);
  --Dark-grayish-cyan: hsl(186, 14%, 43%);
  --Grayish-cyan: hsl(184, 14%, 56%);
  --Light-grayish-cyan: hsl(185, 41%, 84%);
  --Very-light-grayish-cyan: hsl(189, 41%, 97%);
  --White: hsl(0, 0%, 100%);
}

/** Reset **/
html {
  box-sizing: border-box;
  font-size: 16px;
  font-family: "Space Mono", monospace;
}

*,
*::before,
*::after {
  margin: 0;
  padding: 0;
  box-sizing: inherit;
  text-decoration: none;
  transition: all 0.2s ease;
}

body {
  background-color: var(--Light-grayish-cyan);
}

header {
  margin: 4rem auto 0;
  text-align: center;
}

h1 {
  display: none;
}

h2 {
  font-size: 1rem;
}

input {
  font-family: inherit;
  font-size: 1.3rem;
  color: var(--Very-dark-cyan);
  outline: none;
  text-align: end;
  border: none;
}

input[type="number"]::-webkit-inner-spin-button,
input[type="number"]::-webkit-outer-spin-button {
  -webkit-appearance: none;
}

input::placeholder {
  color: var(--Grayish-cyan);
}

h2:first-of-type ~ h2 {
  margin-top: 2rem;
}

/** Page styles **/
.main-container {
  background-color: var(--White);
  border-radius: 1.3rem;
  box-shadow: 0 0 20px rgba(0, 0, 0, 0.1);
  color: var(--Dark-grayish-cyan);
  margin: 2.5rem auto 0;
  padding-bottom: 2rem;
  width: 375px;
}

.form {
  padding: 2rem;
}

.error {
  color: #f44336;
  position: absolute;
  right: 1rem;
  top: -2rem;
  opacity: 0;
}

.error.active {
  opacity: 1;
}

.bill,
.people {
  position: relative;
  align-items: center;
  border-radius: 0.35rem;
  border: 2px solid transparent;
  display: flex;
  justify-content: space-between;
  margin-top: 0.5rem;
  padding: 0.3rem 0.8rem;
}

.bill.active,
.people.active {
  border-color: #f44336 !important;
}

.tip {
  display: flex;
  flex-wrap: wrap;
  gap: 0.9rem;
  margin-top: 0.8rem;
}

.tip input {
  background-color: var(--Very-dark-cyan);
  border: none;
  border-radius: 0.3rem;
  padding: 0.35rem;
  color: var(--Light-grayish-cyan);
  text-align: center;
  width: 148px;
}

.tip input:not([disabled]) {
  background-color: unset;
  color: var(--Very-dark-cyan);
  text-align: end;
  padding-right: 1rem;
  border: 2px solid transparent;
}

.tip input:not([disabled])::placeholder {
  color: var(--Dark-grayish-cyan);
}

.tip input[type="text"].active {
  background-color: var(--Strong-cyan);
  color: var(--Very-dark-cyan);
}

.screen {
  background-color: var(--Very-dark-cyan);
  border-radius: 0.8rem;
  margin: 0 1.5rem;
  padding: 2rem 1.5rem 1.5rem;
}

.screen > div {
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.person-amount {
  margin-top: 1.5rem;
}

.screen > div > span {
  font-size: 2.2rem;
  color: var(--Strong-cyan);
}

.screen h2 {
  font-size: 1rem;
  color: var(--Light-grayish-cyan);
}

.screen h2 > span {
  color: var(--Grayish-cyan);
}

.screen-btn {
  border: none;
  border-radius: 0.3rem;
  background-color: hsla(172, 67%, 45%, 0.1);
  color: var(--Very-dark-cyan);
  font-family: inherit;
  font-size: 1.2rem;
  margin-top: 1.5rem;
  padding: 0.7rem;
  text-transform: uppercase;
  width: 100%;
}

.screen-btn.active {
  background-color: var(--Strong-cyan);
}

.attribution {
  margin-top: 1rem;
  font-size: 11px;
  text-align: center;
}

.attribution a {
  color: var(--Very-dark-cyan);
}

@media (hover: hover) {
  .bill:hover,
  .people:hover,
  .tip input:not([disabled]):hover {
    border-color: var(--Strong-cyan);
  }

  .tip input[type="text"]:hover {
    background-color: var(--Light-grayish-cyan);
    color: var(--Very-dark-cyan);
    cursor: pointer;
  }

  .screen-btn.active:hover {
    background-color: var(--Light-grayish-cyan);
    cursor: pointer;
  }
}

@media (min-width: 1024px) {
  header {
    margin-top: 8rem;
  }

  .main-container {
    width: 920px;
    display: flex;
    padding: 2rem 2rem 2rem 3rem;
    gap: 2rem;
  }

  .form {
    padding: 0;
    flex: 0 1 400px;
  }

  .tip input {
    height: 46px;
    width: 120px;
  }

  .tip input:not([disabled]) {
    font-size: 1.6rem;
    padding-right: 0.8rem;
  }

  .screen {
    flex-grow: 1;
    margin: 0;
  }

  .person-amount {
    margin-top: 1rem;
  }

  .screen > div > span {
    font-size: 3rem;
  }

  .screen-btn {
    margin-top: 6.4rem;
  }
}