/* =========================================================
   Class Cost — style.css
   Art direction: warm cream paper + deep ink + one terracotta
   accent. Editorial serif display (Instrument Serif) over a
   neutral sans (Inter). Humor-forward, shareable, calm.
   ========================================================= */

:root,
[data-theme='light'] {
  /* Surfaces — warm cream "paper" */
  --color-bg: #fbf6ec;
  --color-surface: #ffffff;
  --color-surface-2: #fffdf7;
  --color-surface-offset: #f3ecdd;
  --color-surface-offset-2: #ece3ce;
  --color-divider: #e4d9bf;
  --color-border: #d1c3a3;

  /* Ink */
  --color-text: #1a1a1a;
  --color-text-muted: #5a5448;
  --color-text-faint: #8a8372;
  --color-text-inverse: #fbf6ec;

  /* Accent — Terracotta (muted, warm, not punitive) */
  --color-primary: #b8391f;
  --color-primary-hover: #8f2912;
  --color-primary-active: #661a0b;
  --color-primary-highlight: #f2d9ce;

  --color-accent-soft: #efe0c8;

  --color-success: #437a22;

  /* Radius */
  --radius-sm: 0.375rem;
  --radius-md: 0.625rem;
  --radius-lg: 1rem;
  --radius-xl: 1.5rem;
  --radius-full: 9999px;

  /* Transitions */
  --transition-interactive: 180ms cubic-bezier(0.16, 1, 0.3, 1);

  /* Shadows — soft, warm-toned */
  --shadow-sm: 0 1px 2px rgb(40 30 10 / 0.06);
  --shadow-md: 0 8px 24px rgb(40 30 10 / 0.08);
  --shadow-lg: 0 24px 56px rgb(40 30 10 / 0.12);

  /* Widths */
  --content-narrow: 640px;
  --content-default: 1040px;
  --content-wide: 1200px;

  /* Type scale */
  --text-xs: clamp(0.75rem, 0.7rem + 0.25vw, 0.875rem);
  --text-sm: clamp(0.875rem, 0.82rem + 0.3vw, 1rem);
  --text-base: clamp(1rem, 0.95rem + 0.25vw, 1.0625rem);
  --text-lg: clamp(1.125rem, 1rem + 0.6vw, 1.375rem);
  --text-xl: clamp(1.5rem, 1.2rem + 1.2vw, 2rem);
  --text-2xl: clamp(2rem, 1.4rem + 2.5vw, 3rem);
  --text-hero: clamp(2.75rem, 1.5rem + 5vw, 5.5rem);

  /* Spacing */
  --space-1: 0.25rem;
  --space-2: 0.5rem;
  --space-3: 0.75rem;
  --space-4: 1rem;
  --space-5: 1.25rem;
  --space-6: 1.5rem;
  --space-8: 2rem;
  --space-10: 2.5rem;
  --space-12: 3rem;
  --space-16: 4rem;
  --space-20: 5rem;
  --space-24: 6rem;
  --space-32: 8rem;

  /* Fonts */
  --font-display: 'Instrument Serif', Georgia, 'Times New Roman', serif;
  --font-body: 'Inter', 'Helvetica Neue', system-ui, sans-serif;
}

/* DARK MODE — warm charcoal paper */
[data-theme='dark'] {
  --color-bg: #171411;
  --color-surface: #1f1b17;
  --color-surface-2: #252119;
  --color-surface-offset: #2b2620;
  --color-surface-offset-2: #332c24;
  --color-divider: #3a3327;
  --color-border: #4a4132;

  --color-text: #f1e8d4;
  --color-text-muted: #a8a08e;
  --color-text-faint: #736d5f;
  --color-text-inverse: #171411;

  --color-primary: #e27453;
  --color-primary-hover: #ec8b6e;
  --color-primary-active: #f4a084;
  --color-primary-highlight: #3a2319;

  --color-accent-soft: #2b2620;

  --shadow-sm: 0 1px 2px rgb(0 0 0 / 0.3);
  --shadow-md: 0 8px 24px rgb(0 0 0 / 0.4);
  --shadow-lg: 0 24px 56px rgb(0 0 0 / 0.55);
}

/* System preference fallback */
@media (prefers-color-scheme: dark) {
  :root:not([data-theme]) {
    --color-bg: #171411;
    --color-surface: #1f1b17;
    --color-surface-2: #252119;
    --color-surface-offset: #2b2620;
    --color-surface-offset-2: #332c24;
    --color-divider: #3a3327;
    --color-border: #4a4132;
    --color-text: #f1e8d4;
    --color-text-muted: #a8a08e;
    --color-text-faint: #736d5f;
    --color-text-inverse: #171411;
    --color-primary: #e27453;
    --color-primary-hover: #ec8b6e;
    --color-primary-active: #f4a084;
    --color-primary-highlight: #3a2319;
    --color-accent-soft: #2b2620;
  }
}

/* ========================================================= BASE */
*,
*::before,
*::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  -webkit-text-size-adjust: none;
  text-size-adjust: none;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  text-rendering: optimizeLegibility;
  scroll-behavior: smooth;
  scroll-padding-top: 5rem;
}

body {
  min-height: 100dvh;
  line-height: 1.6;
  font-family: var(--font-body);
  font-size: var(--text-base);
  color: var(--color-text);
  background: var(--color-bg);
  /* Subtle paper grain using layered radial gradients */
  background-image:
    radial-gradient(ellipse 80% 50% at 50% -10%, var(--color-accent-soft), transparent 70%),
    radial-gradient(ellipse 40% 30% at 90% 80%, var(--color-surface-offset), transparent 70%);
  background-attachment: fixed;
}

img,
picture,
svg,
canvas {
  display: block;
  max-width: 100%;
  height: auto;
}

input,
button,
textarea,
select {
  font: inherit;
  color: inherit;
}

h1,
h2,
h3 {
  text-wrap: balance;
  line-height: 1.1;
  font-family: var(--font-display);
  font-weight: 400;
  letter-spacing: -0.01em;
}

p {
  text-wrap: pretty;
  max-width: 65ch;
}

a {
  color: var(--color-primary);
  text-decoration: underline;
  text-decoration-thickness: 1.5px;
  text-underline-offset: 3px;
  text-decoration-color: color-mix(in oklab, var(--color-primary) 40%, transparent);
}
a:hover {
  text-decoration-color: currentColor;
}

::selection {
  background: var(--color-primary-highlight);
  color: var(--color-text);
}

:focus-visible {
  outline: 2px solid var(--color-primary);
  outline-offset: 3px;
  border-radius: var(--radius-sm);
}

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

button {
  cursor: pointer;
  background: none;
  border: none;
  font: inherit;
  color: inherit;
}

a,
button,
input,
textarea,
select {
  transition:
    color var(--transition-interactive),
    background var(--transition-interactive),
    border-color var(--transition-interactive),
    box-shadow var(--transition-interactive),
    transform var(--transition-interactive);
}

.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border-width: 0;
}

/* Skip link — off-screen until keyboard focus (WCAG 2.4.1) */
.skip-link {
  position: absolute;
  top: 0;
  left: 0;
  transform: translateY(-120%);
  background: var(--color-primary);
  color: var(--color-text-inverse);
  padding: var(--space-2) var(--space-4);
  margin: var(--space-4);
  border-radius: var(--radius-sm);
  text-decoration: none;
  font-weight: 600;
  z-index: 100;
}
.skip-link:focus,
.skip-link:focus-visible {
  transform: translateY(0);
}

/* ========================================================= LAYOUT */
.container {
  width: 100%;
  max-width: var(--content-default);
  margin-inline: auto;
  padding-inline: clamp(var(--space-4), 4vw, var(--space-8));
}

/* ========================================================= HEADER */
.site-header {
  position: sticky;
  top: 0;
  z-index: 50;
  background: color-mix(in oklab, var(--color-bg) 88%, transparent);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid transparent;
}
.site-header__inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 4rem;
}

.logo {
  display: inline-flex;
  align-items: center;
  gap: var(--space-3);
  color: var(--color-primary);
  text-decoration: none;
  font-family: var(--font-display);
  font-size: 1.375rem;
}
.logo__word {
  color: var(--color-text);
  letter-spacing: -0.01em;
}
.logo__word em {
  font-style: italic;
  color: var(--color-primary);
}

.theme-toggle {
  width: 2.25rem;
  height: 2.25rem;
  border-radius: var(--radius-full);
  display: grid;
  place-items: center;
  color: var(--color-text-muted);
  border: 1px solid var(--color-border);
  background: var(--color-surface);
}
.theme-toggle:hover {
  color: var(--color-text);
  border-color: var(--color-text-muted);
}

/* ========================================================= HERO */
.hero {
  padding-block: clamp(var(--space-12), 10vw, var(--space-24));
  text-align: left;
}

.eyebrow {
  font-size: var(--text-xs);
  font-weight: 600;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--color-primary);
  margin-bottom: var(--space-5);
}

.hero__title {
  font-size: var(--text-hero);
  font-family: var(--font-display);
  font-weight: 400;
  line-height: 0.98;
  letter-spacing: -0.025em;
  max-width: 16ch;
}
.hero__title .hero__accent {
  color: var(--color-primary);
  font-style: italic;
  white-space: nowrap;
}

.hero__lede {
  margin-top: var(--space-6);
  font-size: var(--text-lg);
  color: var(--color-text-muted);
  max-width: 44ch;
  line-height: 1.5;
}
.hero__lede em {
  font-family: var(--font-display);
  font-style: italic;
  font-size: 1.1em;
  color: var(--color-text);
}

.hero__cta {
  margin-top: var(--space-8);
}

/* ========================================================= BUTTONS */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-2);
  padding: var(--space-3) var(--space-6);
  border-radius: var(--radius-full);
  font-size: var(--text-sm);
  font-weight: 600;
  text-decoration: none;
  border: 1px solid transparent;
  min-height: 44px; /* WCAG 2.5.8 target size */
  white-space: nowrap;
  line-height: 1;
}
.btn--primary {
  background: var(--color-primary);
  color: var(--color-text-inverse);
}
.btn--primary:hover {
  background: var(--color-primary-hover);
  transform: translateY(-1px);
  box-shadow: var(--shadow-md);
}
.btn--primary:active {
  transform: translateY(0);
}

.btn--secondary {
  background: var(--color-surface);
  color: var(--color-text);
  border-color: var(--color-border);
}
.btn--secondary:hover {
  border-color: var(--color-text);
}

.btn--ghost {
  background: transparent;
  color: var(--color-text-muted);
  border-color: transparent;
}
.btn--ghost:hover {
  color: var(--color-text);
}

.btn--sm {
  min-height: 36px;
  padding: var(--space-2) var(--space-4);
  font-size: var(--text-xs);
}

/* ========================================================= CALC SECTION */
.calc {
  padding-block: clamp(var(--space-10), 8vw, var(--space-20));
}

.calc__grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--space-8);
  align-items: start;
}
@media (min-width: 880px) {
  .calc__grid {
    grid-template-columns: 1fr 1fr;
    gap: var(--space-10);
  }
}

.section-title {
  font-size: var(--text-xl);
  margin-bottom: var(--space-6);
  color: var(--color-text);
}

/* ========================================================= FORM */
.calc__form {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-xl);
  padding: clamp(var(--space-5), 4vw, var(--space-8));
  box-shadow: var(--shadow-sm);
}

.field {
  margin-bottom: var(--space-5);
}
.field > label,
.field > legend {
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  font-size: var(--text-sm);
  font-weight: 600;
  margin-bottom: var(--space-2);
  color: var(--color-text);
}
.field legend {
  padding: 0;
  margin-bottom: var(--space-3);
}

.field-row {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--space-4);
  margin-bottom: var(--space-5);
}
.field-row > .field {
  margin-bottom: 0;
}

input[type='text'],
input[type='number'] {
  width: 100%;
  padding: var(--space-3) var(--space-4);
  background: var(--color-surface-2);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  font-size: var(--text-base);
  color: var(--color-text);
  min-height: 44px;
}
input[type='text']::placeholder,
input[type='number']::placeholder {
  color: var(--color-text-faint);
}
input[type='text']:hover,
input[type='number']:hover {
  border-color: var(--color-text-muted);
}
input[type='text']:focus,
input[type='number']:focus {
  outline: none;
  border-color: var(--color-primary);
  box-shadow: 0 0 0 3px var(--color-primary-highlight);
}

.input-with-prefix,
.input-with-suffix {
  position: relative;
  display: flex;
  align-items: center;
}
.input-prefix,
.input-suffix {
  position: absolute;
  color: var(--color-text-muted);
  font-weight: 500;
  pointer-events: none;
}
.input-prefix {
  left: var(--space-4);
}
.input-with-prefix input {
  padding-left: calc(var(--space-4) + 1ch + var(--space-1));
}
.input-suffix {
  right: var(--space-4);
}
.input-with-suffix input {
  padding-right: calc(var(--space-4) + 2ch + var(--space-1));
}

.help {
  font-size: var(--text-xs);
  color: var(--color-text-muted);
  margin-top: var(--space-2);
  line-height: 1.5;
}
.help strong {
  color: var(--color-text);
  font-weight: 600;
}

.tooltip-trigger {
  width: 18px;
  height: 18px;
  border-radius: var(--radius-full);
  background: var(--color-surface-offset);
  color: var(--color-text-muted);
  font-size: 11px;
  font-weight: 700;
  display: inline-grid;
  place-items: center;
  border: 1px solid var(--color-border);
  line-height: 1;
}
.tooltip-trigger:hover {
  background: var(--color-primary);
  color: var(--color-text-inverse);
  border-color: var(--color-primary);
}

/* Radio group */
fieldset {
  border: none;
}
.radio-group {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--space-2);
}
@media (max-width: 480px) {
  .radio-group {
    grid-template-columns: 1fr;
  }
}
.radio {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  padding: var(--space-3) var(--space-4);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  background: var(--color-surface-2);
  cursor: pointer;
  font-size: var(--text-sm);
  min-height: 44px;
}
.radio:hover {
  border-color: var(--color-text-muted);
}
.radio:has(input:checked) {
  border-color: var(--color-primary);
  background: var(--color-primary-highlight);
  color: var(--color-text);
}
.radio input[type='radio'] {
  accent-color: var(--color-primary);
  width: 1rem;
  height: 1rem;
  flex-shrink: 0;
}

/* Switch */
.switch {
  display: inline-flex;
  align-items: center;
  gap: var(--space-3);
  cursor: pointer;
  user-select: none;
}
.switch input {
  position: absolute;
  opacity: 0;
  width: 0;
  height: 0;
}
.switch__slider {
  position: relative;
  width: 42px;
  height: 24px;
  background: var(--color-surface-offset-2);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-full);
  transition: background var(--transition-interactive);
  flex-shrink: 0;
}
.switch__slider::before {
  content: '';
  position: absolute;
  top: 2px;
  left: 2px;
  width: 18px;
  height: 18px;
  background: var(--color-surface);
  border-radius: 50%;
  transition: transform var(--transition-interactive);
  box-shadow: var(--shadow-sm);
}
.switch input:checked ~ .switch__slider {
  background: var(--color-primary);
  border-color: var(--color-primary);
}
.switch input:checked ~ .switch__slider::before {
  transform: translateX(18px);
}
.switch input:focus-visible ~ .switch__slider {
  outline: 2px solid var(--color-primary);
  outline-offset: 3px;
}
.switch__label {
  font-size: var(--text-sm);
  font-weight: 500;
}

.loan-fieldset {
  margin-top: var(--space-2);
  padding-top: var(--space-5);
  border-top: 1px dashed var(--color-divider);
}
.loan-fieldset legend {
  padding-right: var(--space-2);
}
.loan-fields {
  margin-top: var(--space-4);
}
.loan-fields[hidden] {
  display: none;
}

/* ========================================================= RESULT */
.result {
  position: sticky;
  top: 5rem;
}
@media (max-width: 879px) {
  .result {
    position: static;
  }
}

.result__card {
  background: linear-gradient(
    160deg,
    var(--color-surface) 0%,
    var(--color-surface-offset) 100%
  );
  border: 1px solid var(--color-border);
  border-radius: var(--radius-xl);
  padding: clamp(var(--space-6), 4vw, var(--space-10));
  box-shadow: var(--shadow-md);
  position: relative;
  overflow: hidden;
}
.result__card::before {
  content: '';
  position: absolute;
  top: -60%;
  right: -30%;
  width: 80%;
  aspect-ratio: 1;
  border-radius: 50%;
  background: radial-gradient(
    circle,
    var(--color-primary-highlight) 0%,
    transparent 70%
  );
  opacity: 0.7;
  pointer-events: none;
}
.result__card > * {
  position: relative;
}

.result__eyebrow {
  font-size: var(--text-sm);
  color: var(--color-text-muted);
  font-weight: 500;
  margin-bottom: var(--space-3);
}

.result__big {
  font-family: var(--font-display);
  font-size: clamp(3.5rem, 8vw, 6rem);
  font-weight: 400;
  color: var(--color-primary);
  line-height: 1;
  letter-spacing: -0.03em;
  font-feature-settings: 'tnum' on;
  margin-bottom: var(--space-3);
}
.result__currency {
  font-size: 0.55em;
  vertical-align: top;
  margin-right: 0.05em;
  font-feature-settings: 'tnum' on;
}

.result__caption {
  font-size: var(--text-sm);
  color: var(--color-text-muted);
  margin-bottom: var(--space-6);
}

.result__loan {
  margin-top: var(--space-5);
  padding-top: var(--space-5);
  border-top: 1px dashed var(--color-divider);
}
.result__divider {
  display: none;
}
.result__loan-label {
  font-size: var(--text-xs);
  font-weight: 600;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--color-text-muted);
  margin-bottom: var(--space-2);
}
.result__loan-value {
  font-family: var(--font-display);
  font-size: clamp(2rem, 4vw, 2.75rem);
  color: var(--color-text);
  line-height: 1;
  letter-spacing: -0.02em;
  margin-bottom: var(--space-2);
  font-feature-settings: 'tnum' on;
}

.equivalences {
  list-style: none;
  margin-top: var(--space-6);
  padding: var(--space-4) 0;
  border-top: 1px solid var(--color-divider);
  border-bottom: 1px solid var(--color-divider);
  display: grid;
  gap: var(--space-2);
}
.equivalences li {
  font-size: var(--text-sm);
  color: var(--color-text-muted);
  display: flex;
  align-items: baseline;
  gap: var(--space-2);
}
.equivalences li::before {
  content: '=';
  color: var(--color-primary);
  font-weight: 600;
}
.equivalences li strong {
  color: var(--color-text);
  font-weight: 600;
}

.result__footnote {
  margin-top: var(--space-5);
  font-family: var(--font-display);
  font-style: italic;
  font-size: var(--text-lg);
  color: var(--color-text);
  line-height: 1.3;
  max-width: 32ch;
}

.result__actions {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-3);
  margin-top: var(--space-6);
}

/* ========================================================= NOTE */
.note {
  padding-block: var(--space-10);
  text-align: center;
}
.note p {
  margin: 0 auto;
  font-size: var(--text-sm);
  color: var(--color-text-muted);
  max-width: 50ch;
}

/* ========================================================= METHOD */
.method {
  padding-block: clamp(var(--space-12), 10vw, var(--space-24));
  background: var(--color-surface-offset);
  border-block: 1px solid var(--color-divider);
}
.method__grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--space-10);
}
@media (min-width: 880px) {
  .method__grid {
    grid-template-columns: 5fr 7fr;
    gap: var(--space-16);
    align-items: start;
  }
}

.method__lede {
  color: var(--color-text-muted);
  font-size: var(--text-base);
  max-width: 32ch;
}

.method__list {
  list-style: none;
  counter-reset: steps;
  display: grid;
  gap: var(--space-8);
}
.method__list li {
  counter-increment: steps;
  position: relative;
  padding-left: var(--space-10);
}
.method__list li::before {
  content: counter(steps, decimal-leading-zero);
  position: absolute;
  left: 0;
  top: 0;
  font-family: var(--font-display);
  font-size: var(--text-lg);
  color: var(--color-primary);
  font-style: italic;
}
.method__list h3 {
  font-family: var(--font-body);
  font-weight: 600;
  font-size: var(--text-base);
  margin-bottom: var(--space-2);
  letter-spacing: 0;
}
.method__list p {
  color: var(--color-text-muted);
  font-size: var(--text-sm);
  line-height: 1.65;
}
code {
  font-family: ui-monospace, SFMono-Regular, Menlo, monospace;
  font-size: 0.85em;
  background: var(--color-surface);
  padding: 0.1em 0.4em;
  border-radius: var(--radius-sm);
  border: 1px solid var(--color-divider);
  color: var(--color-text);
  word-break: break-word;
  overflow-wrap: anywhere;
}
.method__list p code {
  display: inline-block;
  max-width: 100%;
}

/* ========================================================= FOOTER */
.site-footer {
  padding-block: var(--space-10);
  border-top: 1px solid var(--color-divider);
}
.site-footer__inner {
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: var(--space-4);
}
.site-footer__copy {
  font-size: var(--text-xs);
  color: var(--color-text-muted);
  margin: 0;
}
.site-footer__links {
  display: flex;
  gap: var(--space-5);
  margin: 0;
}
.site-footer__links a {
  color: var(--color-text-muted);
  text-decoration: none;
  font-size: var(--text-xs);
}
.site-footer__links a:hover {
  color: var(--color-primary);
}

/* ========================================================= UTILITIES */
[hidden] {
  display: none !important;
}

/* Number input — hide spinners for cleaner look */
input[type='number']::-webkit-outer-spin-button,
input[type='number']::-webkit-inner-spin-button {
  -webkit-appearance: none;
  margin: 0;
}
input[type='number'] {
  -moz-appearance: textfield;
}