/* ============================================================
   Proportion Calculator — Page Styles
   Inherits: design tokens from index.style.css
   Unique: 4-mode mode-selector grid (icon + label cards),
           proportion-display (A : B = C : X inputs inline),
           proportion-input (large centred Courier number),
           proportion-symbol (: and =),
           results-section with result-box/label/value,
           step-by-step dark mono block with → prefix steps,
           static .faq-item border-top separator pattern
   ============================================================ */

/* ── Page background ── */
body {
  background: var(--clr-slate-100);
}

/* ════════════════════════════════════════
   PAGE HEADER BANNER
   ════════════════════════════════════════ */
.page-header {
  background: var(--clr-slate-900);
  position: relative;
  overflow: hidden;
  padding: 4rem 1.5rem 5rem;
  text-align: center;
  color: var(--clr-white);
}
.page-header::before {
  content: '';
  position: absolute;
  inset: 0;
  background:
    radial-gradient(ellipse 60% 80% at 20% 50%, rgba(13,207,180,.14) 0%, transparent 60%),
    radial-gradient(ellipse 40% 60% at 80% 40%, rgba(34,211,238,.10) 0%, transparent 55%);
}
.page-header::after {
  content: '';
  position: absolute;
  inset: 0;
  background-image:
    linear-gradient(rgba(13,207,180,.05) 1px, transparent 1px),
    linear-gradient(90deg, rgba(13,207,180,.05) 1px, transparent 1px);
  background-size: 48px 48px;
}
.page-header-inner {
  position: relative;
  z-index: 1;
  max-width: 780px;
  margin: 0 auto;
}
.page-header-badge {
  display: inline-flex;
  align-items: center;
  gap: 0.45rem;
  padding: 0.3rem 1rem;
  border-radius: var(--radius-pill);
  background: rgba(13,207,180,.12);
  border: 1px solid rgba(13,207,180,.3);
  font-size: 0.75rem;
  font-weight: 600;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--clr-teal);
  margin-bottom: 1.25rem;
}
.page-header h1 {
  font-family: var(--font-display);
  font-size: clamp(2rem, 5.5vw, 3.5rem);
  font-weight: 800;
  letter-spacing: 0.01em;
  text-transform: uppercase;
  line-height: 1.05;
  margin-bottom: 1rem;
  position: relative;
  z-index: 1;
}
.page-header h1 .accent {
  font-family: var(--font-serif);
  font-style: italic;
  text-transform: none;
  font-weight: 700;
  letter-spacing: -0.01em;
  background: linear-gradient(135deg, var(--clr-teal) 0%, var(--clr-cyan) 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}
.page-header p {
  font-size: 1.05rem;
  color: rgba(255,255,255,.7);
  line-height: 1.7;
  max-width: 680px;
  margin: 0 auto;
  font-weight: 300;
  position: relative;
  z-index: 1;
}

/* ════════════════════════════════════════
   LAYOUT WRAPPER
   ════════════════════════════════════════ */
.calc-page-wrap {
  max-width: 1100px;
  margin: 0 auto;
  padding: 0 1.5rem;
}

/* ════════════════════════════════════════
   AD SLOTS
   ════════════════════════════════════════ */
.ad-slot {
  margin: 1.75rem 0;
  text-align: center;
}
.ad-label {
  font-size: 0.68rem;
  color: var(--clr-slate-400);
  margin-bottom: 0.35rem;
  text-transform: uppercase;
  letter-spacing: 0.1em;
}

/* ════════════════════════════════════════
   CALCULATOR CARD
   ════════════════════════════════════════ */
.calculator-card {
  background: var(--clr-white);
  border-radius: var(--radius-lg);
  padding: 2.5rem;
  box-shadow: var(--shadow-lift);
  border: 1px solid var(--clr-slate-200);
  margin-top: -2.5rem;
  position: relative;
  z-index: 10;
  animation: slideUp 0.5s ease both;
}
@keyframes slideUp {
  from { opacity: 0; transform: translateY(24px); }
  to   { opacity: 1; transform: translateY(0); }
}

.intro-text {
  color: var(--clr-slate-400);
  font-size: 0.93rem;
  line-height: 1.8;
  margin-bottom: 1.75rem;
  padding-bottom: 1.25rem;
  border-bottom: 1px solid var(--clr-slate-200);
}
.intro-text strong { color: var(--clr-teal-deep); font-weight: 600; }
.intro-text a { color: var(--clr-teal-deep); text-decoration: underline; text-underline-offset: 2px; }

/* ════════════════════════════════════════
   MODE SELECTOR — 4 icon + label cards
   ════════════════════════════════════════ */
.mode-selector {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 0.85rem;
  margin-bottom: 1.75rem;
}
.mode-option {
  padding: 1.1rem 0.6rem 0.85rem;
  background: var(--clr-slate-100);
  border: 2px solid var(--clr-slate-200);
  border-radius: var(--radius-md);
  cursor: pointer;
  text-align: center;
  transition: all var(--transition);
  color: var(--clr-slate-600);
  user-select: none;
}
.mode-option:hover {
  background: var(--clr-teal-glow);
  border-color: rgba(13,207,180,.4);
  color: var(--clr-teal-deep);
  transform: translateY(-2px);
}
.mode-option.active {
  background: var(--clr-teal-deep);
  border-color: var(--clr-teal-deep);
  color: var(--clr-white);
  box-shadow: var(--shadow-teal);
}
.mode-icon {
  font-size: 1.5rem;
  display: block;
  margin-bottom: 0.4rem;
  line-height: 1;
}
.mode-option > div:last-child {
  font-family: var(--font-display);
  font-size: 0.78rem;
  font-weight: 700;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  line-height: 1.2;
}

/* ════════════════════════════════════════
   PROPORTION DISPLAY — A : B = C : X
   ════════════════════════════════════════ */
.proportion-display {
  background: var(--clr-slate-100);
  border: 1px solid var(--clr-slate-200);
  border-radius: var(--radius-md);
  padding: 2rem 1.5rem;
  margin-bottom: 1.5rem;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 1rem;
  flex-wrap: wrap;
}
.proportion-input-wrapper {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 0.4rem;
}
.proportion-label {
  font-family: var(--font-display);
  font-size: 0.75rem;
  font-weight: 700;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--clr-teal-deep);
}
.proportion-input {
  width: 100px;
  padding: 0.9rem 0.5rem;
  border: 2px solid var(--clr-slate-200);
  border-radius: var(--radius-sm);
  font-size: 1.55rem;
  font-weight: 700;
  font-family: 'Courier New', monospace;
  text-align: center;
  color: var(--clr-slate-800);
  background: var(--clr-white);
  transition: all var(--transition);
  box-sizing: border-box;
}
.proportion-input:focus {
  outline: none;
  border-color: var(--clr-teal);
  box-shadow: 0 0 0 3px var(--clr-teal-glow);
  transform: scale(1.04);
}
.proportion-input:disabled {
  background: rgba(13,207,180,.06);
  border-color: rgba(13,207,180,.3);
  color: var(--clr-teal-deep);
  cursor: not-allowed;
}
.proportion-input::placeholder {
  color: var(--clr-slate-300);
  font-size: 1.25rem;
}
.proportion-symbol {
  font-size: 1.75rem;
  font-weight: 900;
  color: var(--clr-teal-deep);
  font-family: 'Courier New', monospace;
  user-select: none;
  padding-top: 1.2rem; /* align with input (below label) */
  line-height: 1;
}

/* ── Calculate button ── */
.calculate-btn {
  width: 100%;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.75rem;
  padding: 1.1rem;
  border: none;
  border-radius: var(--radius-sm);
  cursor: pointer;
  font-family: var(--font-display);
  font-size: 1.1rem;
  font-weight: 700;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--clr-white);
  background: var(--clr-teal-deep);
  box-shadow: var(--shadow-teal);
  transition: all var(--transition);
}
.calculate-btn:hover {
  background: var(--clr-teal);
  color: var(--clr-slate-900);
  transform: translateY(-2px);
  box-shadow: 0 12px 32px rgba(13,207,180,.4);
}
.calculate-btn:active { transform: scale(0.99); }

/* ════════════════════════════════════════
   RESULTS SECTION
   ════════════════════════════════════════ */
.results-section {
  margin-top: 1.75rem;
  padding: 1.5rem;
  background: var(--clr-slate-100);
  border: 1px solid var(--clr-slate-200);
  border-left: 3px solid var(--clr-teal);
  border-radius: var(--radius-md);
  display: none;
  animation: fadeIn 0.35s ease;
}
.results-section.show { display: block; }
@keyframes fadeIn {
  from { opacity: 0; transform: translateY(8px); }
  to   { opacity: 1; transform: translateY(0); }
}

.result-title {
  font-family: var(--font-display);
  font-size: 1.1rem;
  font-weight: 700;
  letter-spacing: 0.05em;
  text-transform: uppercase;
  color: var(--clr-teal-deep);
  margin-bottom: 1.1rem;
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

/* Individual result boxes */
.result-box {
  background: var(--clr-white);
  padding: 0.9rem 1rem;
  border-radius: var(--radius-sm);
  margin-bottom: 0.75rem;
  box-shadow: var(--shadow-soft);
  border: 1px solid var(--clr-slate-200);
}
.result-box:last-child { margin-bottom: 0; }
.result-label {
  font-family: var(--font-display);
  font-size: 0.75rem;
  font-weight: 700;
  letter-spacing: 0.07em;
  text-transform: uppercase;
  color: var(--clr-slate-500);
  margin-bottom: 0.3rem;
}
.result-value {
  font-family: 'Courier New', monospace;
  font-size: 1.1rem;
  font-weight: 700;
  color: var(--clr-teal-deep);
  line-height: 1.4;
  word-break: break-all;
}

/* Step-by-step dark mono block */
.step-by-step {
  background: #111827;
  color: #e5e7eb;
  padding: 1rem 1.1rem;
  border-radius: var(--radius-sm);
  font-family: 'Courier New', monospace;
  font-size: 0.875rem;
  line-height: 1.85;
  margin-top: 0.5rem;
  overflow-x: auto;
}
.step-by-step .step {
  padding-left: 1.4rem;
  position: relative;
  margin-bottom: 0.45rem;
}
.step-by-step .step:last-child { margin-bottom: 0; }
.step-by-step .step::before {
  content: '→';
  position: absolute;
  left: 0;
  color: var(--clr-teal);
  font-weight: 700;
}

/* ── Download buttons ── */
.download-buttons {
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem;
  margin-top: 1.1rem;
}
.download-btn {
  flex: 1 1 150px;
  padding: 0.65rem 1rem;
  background: transparent;
  color: var(--clr-teal);
  border: 1px solid rgba(13,207,180,.4);
  border-radius: var(--radius-pill);
  font-family: var(--font-display);
  font-weight: 600;
  font-size: 0.85rem;
  letter-spacing: 0.05em;
  text-transform: uppercase;
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.4rem;
  transition: all var(--transition);
}
.download-btn:hover {
  background: rgba(13,207,180,.1);
  border-color: var(--clr-teal);
  transform: translateY(-1px);
}

/* ════════════════════════════════════════
   INFO CARDS
   ════════════════════════════════════════ */
.info-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
  gap: 1.25rem;
  margin: 2rem 0;
}
.info-card {
  background: var(--clr-white);
  padding: 1.4rem 1.25rem;
  border-radius: var(--radius-md);
  border: 1px solid var(--clr-slate-200);
  border-left: 3px solid var(--clr-teal);
  box-shadow: var(--shadow-soft);
  transition: all var(--transition);
}
.info-card:hover {
  transform: translateY(-3px);
  box-shadow: var(--shadow-card);
}
.info-card h3 {
  font-family: var(--font-display);
  font-size: 0.95rem;
  font-weight: 700;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  color: var(--clr-slate-800);
  margin-bottom: 0.5rem;
}
.info-card p {
  font-size: 0.875rem;
  color: var(--clr-slate-400);
  line-height: 1.7;
}

/* ════════════════════════════════════════
   BLOG / ARTICLE SECTION
   ════════════════════════════════════════ */
.blog-section {
  max-width: 860px;
  margin: 3rem auto 0;
  padding: 0 1.5rem;
}
.blog-content {
  background: var(--clr-white);
  border-radius: var(--radius-lg);
  padding: 3rem 3.5rem;
  box-shadow: var(--shadow-card);
  border: 1px solid var(--clr-slate-200);
  line-height: 1.9;
}
.blog-content h2 {
  font-family: var(--font-display);
  font-size: clamp(1.5rem, 4vw, 2.2rem);
  font-weight: 700;
  letter-spacing: 0.01em;
  text-transform: uppercase;
  color: var(--clr-slate-800);
  margin-bottom: 0.5rem;
  line-height: 1.15;
}
.blog-content h2 .serif-accent {
  font-family: var(--font-serif);
  font-style: italic;
  text-transform: none;
  background: linear-gradient(135deg, var(--clr-teal-deep), var(--clr-cyan));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}
.meta-line {
  font-size: 0.82rem;
  color: var(--clr-slate-400);
  margin-bottom: 2rem;
  padding-bottom: 1.5rem;
  border-bottom: 1px solid var(--clr-slate-200);
}
.meta-line a { color: var(--clr-teal-deep); text-decoration: underline; text-underline-offset: 2px; }
.blog-content h3 {
  font-family: var(--font-display);
  font-size: 1.3rem;
  font-weight: 700;
  letter-spacing: 0.03em;
  text-transform: uppercase;
  color: var(--clr-slate-800);
  margin-top: 2.5rem;
  margin-bottom: 0.9rem;
}
.blog-content h4 {
  font-family: var(--font-display);
  font-size: 1.05rem;
  font-weight: 700;
  letter-spacing: 0.03em;
  text-transform: uppercase;
  color: var(--clr-slate-700);
  margin-top: 1.75rem;
  margin-bottom: 0.65rem;
}
.blog-content p {
  color: var(--clr-slate-600);
  font-size: 0.975rem;
  margin-bottom: 1.1rem;
  line-height: 1.85;
}
.blog-content ul,
.blog-content ol {
  color: var(--clr-slate-600);
  margin-left: 1.5rem;
  margin-bottom: 1.25rem;
}
.blog-content li {
  margin-bottom: 0.4rem;
  line-height: 1.75;
  font-size: 0.975rem;
}
.blog-content a {
  color: var(--clr-teal-deep);
  text-decoration: underline;
  text-decoration-thickness: 1px;
  text-underline-offset: 2px;
  transition: color var(--transition);
}
.blog-content a:hover { color: var(--clr-teal); }
.blog-content strong { color: var(--clr-slate-800); font-weight: 600; }
.blog-content em { color: var(--clr-slate-600); font-style: italic; }
.blog-content code {
  background: var(--clr-slate-100);
  padding: 0.1rem 0.35rem;
  border-radius: 4px;
  font-family: 'Courier New', monospace;
  font-size: 0.87em;
  color: var(--clr-teal-deep);
  border: 1px solid var(--clr-slate-200);
}

/* formula-box */
.formula-box {
  background: #111827;
  color: #e5e7eb;
  border-radius: var(--radius-sm);
  padding: 1rem 1.1rem;
  margin: 1.1rem 0;
  font-family: 'Courier New', monospace;
  font-size: 0.9rem;
  line-height: 1.75;
  overflow-x: auto;
}
.formula-box strong { color: var(--clr-teal); -webkit-text-fill-color: var(--clr-teal); font-weight: 700; }

/* highlight-box */
.highlight-box {
  background: linear-gradient(135deg, rgba(13,207,180,.06) 0%, rgba(34,211,238,.06) 100%);
  border: 1px solid rgba(13,207,180,.2);
  border-left: 3px solid var(--clr-teal);
  padding: 1.1rem 1.3rem;
  border-radius: var(--radius-sm);
  margin: 1.6rem 0;
  font-size: 0.93rem;
  color: var(--clr-slate-700);
  line-height: 1.7;
}
.highlight-box strong { color: var(--clr-slate-800); font-weight: 600; }
.highlight-box ul {
  margin: 0.5rem 0 0 1.2rem;
  padding: 0;
}
.highlight-box li { margin-bottom: 0.4rem; font-size: 0.93rem; }

/* ════════════════════════════════════════
   FAQ SECTION — static .faq-item with
   border-top separator pattern
   ════════════════════════════════════════ */
.faq-section {
  max-width: 860px;
  margin: 2.5rem auto 4rem;
  padding: 0 1.5rem;
}
.faq-inner {
  background: var(--clr-white);
  border-radius: var(--radius-lg);
  padding: 2.25rem 2.5rem;
  box-shadow: var(--shadow-card);
  border: 1px solid var(--clr-slate-200);
}
.faq-inner h2 {
  font-family: var(--font-display);
  font-size: 1.4rem;
  font-weight: 700;
  letter-spacing: 0.03em;
  text-transform: uppercase;
  color: var(--clr-slate-800);
  margin-top: 0;
  margin-bottom: 1.4rem;
  padding-bottom: 1rem;
  border-bottom: 1px solid var(--clr-slate-200);
}
.faq-item + .faq-item {
  border-top: 1px solid var(--clr-slate-200);
  padding-top: 1rem;
  margin-top: 1rem;
}
.faq-item h3 {
  font-family: var(--font-display);
  font-size: 0.95rem;
  font-weight: 700;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  color: var(--clr-slate-800);
  margin-bottom: 0.35rem;
}
.faq-item p {
  font-size: 0.9rem;
  color: var(--clr-slate-400);
  line-height: 1.75;
  margin: 0;
}
.faq-item strong { color: var(--clr-slate-700); font-weight: 600; }
.faq-item a { color: var(--clr-teal-deep); text-decoration: underline; text-underline-offset: 2px; }

/* ════════════════════════════════════════
   RESPONSIVE
   ════════════════════════════════════════ */
@media (max-width: 768px) {
  .page-header { padding: 3rem 1.25rem 4rem; }
  .page-header h1 { font-size: 1.9rem; }

  .calculator-card {
    padding: 1.5rem 1.25rem;
    margin-top: -1.5rem;
    border-radius: var(--radius-md);
  }
  .mode-selector { grid-template-columns: repeat(2, 1fr); }
  .proportion-display { padding: 1.25rem 0.75rem; gap: 0.65rem; }
  .proportion-input { width: 72px; font-size: 1.2rem; }
  .proportion-symbol { font-size: 1.35rem; }

  .blog-section { padding: 0 1rem; }
  .blog-content { padding: 1.75rem 1.25rem; }
  .blog-content h2 { font-size: 1.35rem; }
  .blog-content h3 { font-size: 1.1rem; }

  .faq-section { padding: 0 1rem; }
  .faq-inner { padding: 1.25rem; }
  .info-grid { grid-template-columns: 1fr; }
  .download-buttons { flex-direction: column; }
}

@media (max-width: 480px) {
  .calc-page-wrap { padding: 0 0.75rem; }
  .proportion-input { width: 62px; font-size: 1rem; padding: 0.6rem 0.25rem; }
  .proportion-symbol { font-size: 1.1rem; }
  .mode-option > div:last-child { font-size: 0.7rem; }
}

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