:root {
  --prussian-blue: #0b132bff;
  --space-indigo: #1c2541ff;
  --dusk-blue: #3a506bff;
  --tropical-teal: #5bc0beff;
  --neon-ice: #6fffe9ff;

  --pacific-cyan: #048ba8;
  --emerald: #16db93;
  --banana-cream: #efea5a;
  --pumpkin-spice: #fa8334;
  --brown-red: #a52422;

  --font-main: monospace;
  --text-main: var(--neon-ice);
  --text-alert: var(--brown-red);
  --text-on-accent: var(--prussian-blue);
  --bg-body: var(--prussian-blue);
  --bg-calculator: var(--space-indigo);
  --bg-input: var(--dusk-blue);
  --bg-button: var(--tropical-teal);
  --bg-button-hover: var(--neon-ice);
  --shadow-focus: #6fffe966;

  --severe-thinness: var(--brown-red);
  --moderate-thinness: var(--pumpkin-spice);
  --mild-thinness: var(--banana-cream);
  --normal-weight: var(--pacific-cyan);
  --overweight: var(--emerald);
  --obese-class-1: var(--banana-cream);
  --obese-class-2: var(--pumpkin-spice);
  --obese-class-3: var(--brown-red);
}

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

body {
  background-color: var(--bg-body);
  color: var(--text-main);
  font-family: var(--font-main);
  width: 100%;
  min-height: 100vh;
  display: flex;
  justify-content: center;
  align-items: center;
}
main {
  width: 100%;
  max-width: 480px;
  padding: 20px;
}
input,
button {
  font-family: var(--font-main);
  border: none;
  outline: none;
}
input:focus-visible,
button:focus-visible {
  box-shadow: 0 0 0 4px var(--shadow-focus);
}

.bmi-calculator {
  background-color: var(--bg-calculator);
  padding: 20px;
  border-radius: 10px;
}
.bmi-calculator__label,
.bmi-calculator__input,
.bmi-calculator__submit-btn,
.bmi-calculator__result,
.bmi-calculator__category,
.bmi-calculator__alert {
  font-size: 1.2rem;
  font-weight: 600;
}
.bmi-calculator__title {
  font-size: 1.6rem;
  text-align: center;
  margin-bottom: 10px;
}
.bmi-calculator__alert {
  color: var(--text-alert);
  font-style: italic;
  text-align: center;
  margin-bottom: 10px;
}
.bmi-calculator__alert--hidden {
  line-height: 0;
  opacity: 0;
}
.bmi-calculator__form {
  display: flex;
  flex-direction: column;
  gap: 20px;
  margin-bottom: 20px;
}
.bmi-calculator__field {
  display: flex;
  flex-direction: column;
  gap: 5px;
}
.bmi-calculator__input {
  background-color: var(--bg-input);
  color: var(--text-main);
  padding: 10px;
  border-radius: 5px;
  -moz-appearance: none;
  appearance: none;
}
.bmi-calculator__input::-webkit-outer-spin-button,
.bmi-calculator__input::-webkit-inner-spin-button {
  -webkit-appearance: none;
}
.bmi-calculator__submit-btn {
  background-color: var(--bg-button);
  color: var(--text-on-accent);
  padding: 10px;
  border-radius: 5px;
  transition: background-color 0.3s ease;
  cursor: pointer;
}
.bmi-calculator__submit-btn:hover {
  background-color: var(--bg-button-hover);
}

.severe-thinness {
  color: var(--severe-thinness);
}
.moderate-thinness {
  color: var(--moderate-thinness);
}
.mild-thinness {
  color: var(--mild-thinness);
}
.normal-weight {
  color: var(--normal-weight);
}
.overweight {
  color: var(--overweight);
}
.obese-class-1 {
  color: var(--obese-class-1);
}
.obese-class-2 {
  color: var(--obese-class-2);
}
.obese-class-3 {
  color: var(--obese-class-3);
}