:root {
  --page-bg: #f4f7fb;
  --surface: #ffffff;
  --ink: #172033;
  --muted: #667085;
  --line: #d9e2ec;
  --brand: #2563eb;
  --brand-dark: #1d4ed8;
  --success-bg: #dcfce7;
  --success-ink: #14532d;
  --shadow: 0 20px 50px rgba(23, 32, 51, 0.12);
}

*,
*::before,
*::after {
  box-sizing: border-box;
}

body {
  min-height: 100vh;
  margin: 0;
  color: var(--ink);
  background:
    linear-gradient(135deg, rgba(37, 99, 235, 0.14), rgba(20, 184, 166, 0.12) 36%, rgba(244, 247, 251, 0) 66%),
    var(--page-bg);
  font-family: Arial, sans-serif;
}

.navbar {
  box-shadow: 0 2px 14px rgba(15, 23, 42, 0.08);
}

.navbar-brand {
  font-weight: 800;
  letter-spacing: 0;
}

.calculator-page {
  padding: clamp(1.5rem, 5vw, 4rem) 0;
}

.calculator-hero {
  max-width: 760px;
  margin: 0 auto clamp(1.5rem, 4vw, 2.5rem);
}

.eyebrow {
  margin: 0 0 0.35rem;
  color: var(--brand);
  font-size: 0.78rem;
  font-weight: 800;
  text-transform: uppercase;
}

.calculator-hero h1 {
  margin: 0;
  font-size: clamp(2rem, 7vw, 3.4rem);
  line-height: 1.05;
  font-weight: 850;
}

.calculator-hero p:not(.eyebrow) {
  margin: 0.9rem auto 0;
  max-width: 620px;
  color: var(--muted);
}

.calculator-shell {
  display: grid;
  grid-template-columns: minmax(0, 1.1fr) minmax(18rem, 0.9fr);
  gap: 1.25rem;
  align-items: stretch;
}

.calculator-card,
.result-card {
  background: rgba(255, 255, 255, 0.96);
  border: 1px solid rgba(217, 226, 236, 0.95);
  border-radius: 8px;
  box-shadow: var(--shadow);
  padding: clamp(1.15rem, 3vw, 2rem);
}

.calculator-card {
  display: grid;
  gap: 1rem;
}

legend,
.result-card h2 {
  margin: 0;
  font-size: 1.45rem;
  font-weight: 850;
}

.form-intro,
.result-copy,
.tip-box p {
  margin: 0;
  color: var(--muted);
}

.field-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 1rem;
}

.field-group {
  display: grid;
  gap: 0.35rem;
}

.form-label {
  margin: 0;
  color: #344054;
  font-size: 0.9rem;
  font-weight: 750;
}

.form-control {
  min-height: 3rem;
  border-color: var(--line);
  border-radius: 6px;
}

.form-control:focus {
  border-color: var(--brand);
  box-shadow: 0 0 0 0.2rem rgba(37, 99, 235, 0.18);
}

.input-prefix,
.input-suffix {
  display: grid;
  align-items: center;
  overflow: hidden;
  background: #ffffff;
  border: 1px solid var(--line);
  border-radius: 6px;
}

.input-prefix {
  grid-template-columns: auto 1fr;
}

.input-suffix {
  grid-template-columns: 1fr auto;
}

.input-prefix span,
.input-suffix span {
  min-width: 3rem;
  padding: 0 0.85rem;
  color: var(--muted);
  font-weight: 800;
  text-align: center;
}

.input-prefix .form-control,
.input-suffix .form-control {
  border: 0;
  border-radius: 0;
}

.input-prefix:has(.is-invalid),
.input-suffix:has(.is-invalid) {
  border-color: #dc3545;
}

.input-prefix:has(.is-valid),
.input-suffix:has(.is-valid) {
  border-color: #198754;
}

.button-row {
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem;
  margin-top: 0.25rem;
}

.btn {
  min-height: 3rem;
  border-radius: 6px;
  font-weight: 800;
}

.btn-primary {
  background: var(--brand);
  border-color: var(--brand);
}

.btn-primary:hover {
  background: var(--brand-dark);
  border-color: var(--brand-dark);
}

.result-card {
  display: grid;
  gap: 1rem;
  align-content: start;
}

.result-alert {
  margin: 0;
  padding: 1.1rem;
  color: var(--success-ink);
  background: var(--success-bg);
  border: 0;
  font-size: 1.35rem;
  font-weight: 900;
}

#alertBox {
  margin: 0;
  border-radius: 8px;
}

.alert-heading {
  margin-bottom: 0.65rem;
  font-weight: 850;
}

.error-list {
  padding-left: 1.15rem;
  margin: 0;
}

.error-list p {
  margin: 0.15rem 0;
}

.tip-box {
  padding: 1rem;
  background: #eff6ff;
  border: 1px solid #bfdbfe;
  border-radius: 8px;
}

.tip-box strong {
  display: block;
  margin-bottom: 0.25rem;
  color: var(--brand-dark);
}

@media (max-width: 767.98px) {
  .calculator-shell,
  .field-grid {
    grid-template-columns: 1fr;
  }

  .calculator-page {
    padding-top: 1.25rem;
  }

  .button-row .btn {
    width: 100%;
  }
}