:root {
  color-scheme: light;
  --page: #f4f5f3;
  --surface: #ffffff;
  --surface-muted: #f8f9f7;
  --text: #1d2421;
  --text-muted: #66706b;
  --label: #39433e;
  --border: #dce1dd;
  --border-strong: #bcc6bf;
  --accent: #1d5b47;
  --accent-dark: #154535;
  --accent-soft: #e9f2ee;
  --on-accent: #ffffff;
  --result-border: #c9ddd4;
  --result-text: #3f5048;
  --error: #a22d2d;
  --focus: rgba(29, 91, 71, 0.16);
  --glow: rgba(29, 91, 71, 0.06);
  --shadow: 0 18px 50px rgba(25, 37, 31, 0.08);
  font-family:
    Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  font-synthesis: none;
}

:root[data-theme="dark"] {
  color-scheme: dark;
  --page: #111714;
  --surface: #18201c;
  --surface-muted: #1d2722;
  --text: #edf2ef;
  --text-muted: #aab6b0;
  --label: #cbd4cf;
  --border: #303c36;
  --border-strong: #4b5a52;
  --accent: #76c6a8;
  --accent-dark: #9bdabd;
  --accent-soft: #1a3027;
  --on-accent: #10241d;
  --result-border: #35634f;
  --result-text: #bed0c7;
  --error: #ff9d9d;
  --focus: rgba(118, 198, 168, 0.25);
  --glow: rgba(118, 198, 168, 0.08);
  --shadow: 0 18px 50px rgba(0, 0, 0, 0.24);
}

@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    color-scheme: dark;
    --page: #111714;
    --surface: #18201c;
    --surface-muted: #1d2722;
    --text: #edf2ef;
    --text-muted: #aab6b0;
    --label: #cbd4cf;
    --border: #303c36;
    --border-strong: #4b5a52;
    --accent: #76c6a8;
    --accent-dark: #9bdabd;
    --accent-soft: #1a3027;
    --on-accent: #10241d;
    --result-border: #35634f;
    --result-text: #bed0c7;
    --error: #ff9d9d;
    --focus: rgba(118, 198, 168, 0.25);
    --glow: rgba(118, 198, 168, 0.08);
    --shadow: 0 18px 50px rgba(0, 0, 0, 0.24);
  }
}

* {
  box-sizing: border-box;
}

body {
  min-width: 320px;
  margin: 0;
  background:
    radial-gradient(circle at top left, var(--glow), transparent 30rem),
    var(--page);
  color: var(--text);
  line-height: 1.5;
}

button,
input,
select {
  font: inherit;
}

button,
select {
  cursor: pointer;
}

.page-shell {
  width: min(100% - 2rem, 74rem);
  margin: 0 auto;
  padding: clamp(2.5rem, 7vw, 5.5rem) 0 2rem;
}

.page-header {
  max-width: 48rem;
  margin: 0 auto 2rem;
  text-align: center;
}

.eyebrow,
.section-number {
  margin: 0 0 0.65rem;
  color: var(--accent);
  font-size: 0.75rem;
  font-weight: 750;
  letter-spacing: 0.12em;
  text-transform: uppercase;
}

h1,
h2,
h3,
h4,
p {
  margin-top: 0;
}

h1 {
  margin-bottom: 0.75rem;
  font-size: clamp(2.15rem, 5vw, 4rem);
  line-height: 1.04;
  letter-spacing: -0.045em;
}

.intro {
  margin-bottom: 0;
  color: var(--text-muted);
  font-size: clamp(1rem, 2vw, 1.14rem);
}

.theme-control {
  display: inline-grid;
  grid-template-columns: auto minmax(7rem, auto);
  align-items: center;
  gap: 0.65rem;
  margin-top: 1.25rem;
  padding: 0.35rem 0.35rem 0.35rem 0.75rem;
  border: 1px solid var(--border);
  border-radius: 0.75rem;
  background: var(--surface);
  color: var(--text-muted);
  font-size: 0.82rem;
}

.theme-control select {
  min-height: 2.25rem;
  padding: 0.35rem 2rem 0.35rem 0.7rem;
  border-color: var(--border);
  font-size: 0.9rem;
  font-weight: 700;
}

.calculator-card {
  overflow: hidden;
  border: 1px solid var(--border);
  border-radius: 1.25rem;
  background: var(--surface);
  box-shadow: var(--shadow);
}

.tabs {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 0.35rem;
  padding: 0.5rem;
  border-bottom: 1px solid var(--border);
  background: var(--surface-muted);
}

.tab {
  min-height: 3rem;
  padding: 0.7rem 1rem;
  border: 1px solid transparent;
  border-radius: 0.75rem;
  background: transparent;
  color: var(--text-muted);
  font-weight: 700;
}

.tab:hover {
  color: var(--text);
}

.tab[aria-selected="true"] {
  border-color: var(--border);
  background: var(--surface);
  color: var(--accent);
  box-shadow: 0 2px 8px rgba(25, 37, 31, 0.05);
}

.panel {
  padding: clamp(1.25rem, 4vw, 2.75rem);
}

.panel-heading {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: 2rem;
  margin-bottom: 2rem;
}

.panel-heading h2 {
  margin-bottom: 0;
  font-size: clamp(1.45rem, 3vw, 2rem);
  line-height: 1.15;
  letter-spacing: -0.025em;
}

.formula {
  flex: none;
  margin: 0;
  padding: 0.7rem 0.9rem;
  border: 1px solid var(--border);
  border-radius: 0.65rem;
  background: var(--surface-muted);
  color: var(--accent-dark);
  font-family: Georgia, "Times New Roman", serif;
  font-size: 1.05rem;
  white-space: nowrap;
}

.field-grid {
  display: grid;
  gap: 1rem;
}

.three-columns {
  grid-template-columns: repeat(3, minmax(0, 1fr));
}

.two-columns,
.options-grid {
  grid-template-columns: repeat(2, minmax(0, 1fr));
}

.options-grid {
  margin-top: 1rem;
}

label {
  display: grid;
  gap: 0.45rem;
  color: var(--label);
  font-size: 0.92rem;
  font-weight: 700;
}

input,
select {
  width: 100%;
  min-height: 3.25rem;
  padding: 0.75rem 0.9rem;
  border: 1px solid var(--border-strong);
  border-radius: 0.65rem;
  outline: none;
  background: var(--surface);
  color: var(--text);
  font-size: 1.05rem;
  font-weight: 500;
  transition:
    border-color 140ms ease,
    box-shadow 140ms ease;
}

input:focus,
select:focus,
button:focus-visible {
  border-color: var(--accent);
  box-shadow: 0 0 0 3px var(--focus);
}

.decimal-field {
  width: min(100%, 15rem);
  margin-top: 1rem;
}

.actions {
  display: flex;
  flex-wrap: wrap;
  gap: 0.7rem;
  margin-top: 0.25rem;
}

.button {
  min-height: 2.9rem;
  padding: 0.65rem 1rem;
  border: 1px solid transparent;
  border-radius: 0.65rem;
  font-weight: 750;
}

.button.primary {
  background: var(--accent);
  color: var(--on-accent);
}

.button.primary:hover {
  background: var(--accent-dark);
}

.button.secondary,
.button.copy {
  border-color: var(--border-strong);
  background: var(--surface);
  color: var(--text);
}

.button.secondary:hover,
.button.copy:hover {
  background: var(--surface-muted);
}

.button.copy {
  margin-left: auto;
}

.error {
  min-height: 1.5rem;
  margin: 0.75rem 0 0;
  color: var(--error);
  font-size: 0.92rem;
  font-weight: 700;
}

.result {
  margin-top: 1.5rem;
  padding: clamp(1.1rem, 3vw, 1.5rem);
  border: 1px solid var(--result-border);
  border-radius: 0.85rem;
  background: var(--accent-soft);
}

.workflow-divider {
  display: flex;
  align-items: center;
  gap: 0.85rem;
  margin: 2.25rem 0;
  color: var(--text-muted);
  font-size: 0.75rem;
  font-weight: 750;
  letter-spacing: 0.12em;
  text-transform: uppercase;
}

.workflow-divider::before,
.workflow-divider::after {
  height: 1px;
  flex: 1;
  background: var(--border);
  content: "";
}

.runtime-heading {
  margin-bottom: 1rem;
}

.field-help {
  margin-bottom: 0.35rem;
  color: var(--text-muted);
}

.field-help code,
.x-status {
  color: var(--accent-dark);
  font-weight: 700;
}

.x-status {
  margin-bottom: 1.25rem;
  font-size: 0.9rem;
}

.result h3 {
  margin-bottom: 0.4rem;
  font-size: 1rem;
  color: var(--accent-dark);
}

.result-summary {
  overflow-wrap: anywhere;
  margin-bottom: 1.25rem;
  font-family: Georgia, "Times New Roman", serif;
  font-size: clamp(1.35rem, 3vw, 1.8rem);
  line-height: 1.25;
}

.result h4 {
  margin-bottom: 0.55rem;
  font-size: 0.9rem;
}

.steps {
  display: grid;
  gap: 0.4rem;
  margin: 0;
  padding-left: 1.35rem;
  color: var(--result-text);
  font-variant-numeric: tabular-nums;
}

.steps li {
  padding-left: 0.25rem;
  overflow-wrap: anywhere;
}

footer {
  padding-top: 1.25rem;
  color: var(--text-muted);
  font-size: 0.85rem;
  text-align: center;
}

footer p {
  margin-bottom: 0;
}

[hidden] {
  display: none !important;
}

@media (max-width: 720px) {
  .tabs {
    grid-template-columns: 1fr;
  }

  .three-columns,
  .two-columns,
  .options-grid {
    grid-template-columns: 1fr;
  }

  .panel-heading {
    display: grid;
    gap: 1rem;
  }

  .formula {
    justify-self: start;
  }
}

@media (max-width: 460px) {
  .page-shell {
    width: min(100% - 1rem, 74rem);
    padding-top: 1.75rem;
  }

  .calculator-card {
    border-radius: 0.9rem;
  }

  .button {
    flex: 1 1 calc(50% - 0.7rem);
  }

  .button.copy {
    flex-basis: 100%;
    margin-left: 0;
  }
}

@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    scroll-behavior: auto !important;
    transition-duration: 0.01ms !important;
  }
}