body {
  display: flex;
  justify-content: center;
  align-items: center;

  min-height: 100vh;
  width: 100vw;

  background: #1e90ff;
}

.container {
  --size: 600px;
  --color1: #70a1ff;
  --color2: #30336b;
  --duration: 0.4s;

  display: flex;
  justify-content: center;
  align-items: center;
  flex-direction: column;

  color: white;
}
.tip {
  font-size: 1.5rem;
}
.container .cup.a-day {
  --cup-size: calc(var(--size) * 1);

  display: flex;
  justify-content: center;
  align-items: center;
  flex-direction: column;

  overflow: hidden;
}
.container .cup.a-day .air {
  display: flex;
  justify-content: center;
  align-items: center;
  flex-direction: column;

  flex-grow: 1;

  overflow: hidden;
}
.container .cup.a-day .air .l {
  font-size: 2rem;
}
.container .cup.a-day .air p {
  margin: 0;
  padding: 0;
}
.container .cup.a-day .water {
  display: flex;
  justify-content: center;
  align-items: center;

  flex-shrink: 0;

  height: 0%;
  width: 100%;

  color: white;
  font-size: 2rem;
  background-color: var(--color1);

  overflow: hidden;

  transition: all var(--duration) ease-in-out;
}

.container .cups {
  display: flex;
  justify-content: center;
  align-items: center;
  flex-direction: column;
}
.container .cups .row {
  display: flex;
}
.cups {
  --cup-size: calc(var(--size) * 0.3);
}
.cups .cup {
  display: flex;
  justify-content: center;
  align-items: center;

  margin: calc(var(--cup-size) * 0.1) calc(var(--cup-size) * 0.1);

  font-size: 1.3rem;

  transition: color var(--duration) ease-in-out,
    background-color var(--duration) ease-in-out;
}
.cups .cup.full {
  color: white;
  background-color: var(--color1);
}
.cup {
  width: calc(var(--cup-size) * 0.6);
  height: var(--cup-size);

  background-color: white;
  color: var(--color1);
  outline: 8px solid var(--color2);
  border-radius: 0 0 calc(var(--cup-size) * 0.1) calc(var(--cup-size) * 0.1);
}