/* ============================================================
   Decimal Calculator — Page Styles
   Inherits: design tokens from index.style.css
   Unique: 4-mode operation-grid (large symbol + label),
           input-grid (num1 | op-symbol | num2),
           quick-examples chip buttons,
           step-item left-border breakdown cards,
           result-details with detail-section/content,
           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);
}

/* ════════════════════════════════════════
   OPERATION GRID — 4 large symbol cards
   ════════════════════════════════════════ */
.form-group {
  margin-bottom: 1.5rem;
}
.form-label {
  display: block;
  font-family: var(--font-display);
  font-weight: 700;
  font-size: 0.82rem;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--clr-slate-600);
  margin-bottom: 0.75rem;
}
.operation-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 0.85rem;
  margin-bottom: 1.5rem;
}
.operation-btn {
  padding: 1.25rem 0.75rem 1rem;
  background: var(--clr-slate-100);
  border: 3px solid var(--clr-slate-200);
  border-radius: var(--radius-md);
  cursor: pointer;
  text-align: center;
  transition: all var(--transition);
  color: var(--clr-slate-700);
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 0.4rem;
  user-select: none;
}
.operation-btn > span:first-child {
  font-size: 2rem;
  font-weight: 900;
  line-height: 1;
  font-family: 'Courier New', monospace;
}
.operation-btn:hover {
  background: var(--clr-teal-glow);
  border-color: rgba(13,207,180,.4);
  color: var(--clr-teal-deep);
  transform: translateY(-2px);
}
.operation-btn.active {
  background: var(--clr-teal-deep);
  border-color: var(--clr-teal-deep);
  color: var(--clr-white);
  box-shadow: var(--shadow-teal);
}
.operation-label {
  font-family: var(--font-display);
  font-size: 0.75rem;
  font-weight: 700;
  letter-spacing: 0.07em;
  text-transform: uppercase;
}

/* ════════════════════════════════════════
   INPUT GRID — num1 | symbol | num2
   ════════════════════════════════════════ */
.input-grid {
  display: grid;
  grid-template-columns: 1fr auto 1fr;
  gap: 1.25rem;
  align-items: center;
  margin-bottom: 1.25rem;
}
.form-input {
  width: 100%;
  padding: 0.95rem 1rem;
  border: 2px solid var(--clr-slate-200);
  border-radius: var(--radius-sm);
  font-size: 1.15rem;
  font-family: 'Courier New', monospace;
  font-weight: 700;
  color: var(--clr-slate-800);
  background: var(--clr-slate-100);
  transition: all var(--transition);
  box-sizing: border-box;
}
.form-input:focus {
  outline: none;
  border-color: var(--clr-teal);
  background: var(--clr-white);
  box-shadow: 0 0 0 3px var(--clr-teal-glow);
}
.form-input::placeholder {
  color: var(--clr-slate-300);
  font-size: 0.88rem;
  font-weight: 400;
}
.input-hint {
  font-size: 0.78rem;
  color: var(--clr-slate-400);
  margin-top: 0.45rem;
  font-style: italic;
  line-height: 1.5;
}

/* Central operation symbol display */
.op-symbol {
  text-align: center;
  font-size: 2.5rem;
  font-weight: 900;
  color: var(--clr-teal-deep);
  font-family: 'Courier New', monospace;
  padding-top: 1.4rem; /* aligns with input vertically */
  user-select: none;
  line-height: 1;
}

/* ── Quick example chip buttons ── */
.quick-examples {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 0.5rem;
  margin-bottom: 0.5rem;
}
.examples-label {
  font-family: var(--font-display);
  font-size: 0.78rem;
  font-weight: 700;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--clr-slate-500);
}
.example-btn {
  padding: 0.38rem 0.85rem;
  background: var(--clr-white);
  border: 1px solid var(--clr-slate-200);
  border-radius: var(--radius-sm);
  cursor: pointer;
  font-size: 0.8rem;
  font-family: 'Courier New', monospace;
  color: var(--clr-slate-600);
  transition: all var(--transition);
}
.example-btn:hover {
  background: var(--clr-teal-glow);
  border-color: rgba(13,207,180,.4);
  color: var(--clr-teal-deep);
  transform: translateY(-1px);
}

/* ── Calculate button ── */
.calculate-btn {
  width: 100%;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.6rem;
  padding: 1rem;
  border: none;
  border-radius: var(--radius-sm);
  cursor: pointer;
  font-family: var(--font-display);
  font-size: 1.05rem;
  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);
  margin-top: 1.25rem;
}
.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); }

/* ════════════════════════════════════════
   RESULT CONTAINER
   ════════════════════════════════════════ */
.result-container {
  margin-top: 1.9rem;
  display: none;
  animation: resultSlide 0.4s ease;
}
.result-container.show { display: block; }
@keyframes resultSlide {
  from { opacity: 0; transform: scale(0.97); }
  to   { opacity: 1; transform: scale(1); }
}

/* Hero answer */
.result-card {
  background: var(--clr-teal-deep);
  border-radius: var(--radius-md);
  padding: 1.5rem 1.25rem;
  text-align: center;
  color: var(--clr-white);
  margin-bottom: 1.25rem;
}
.result-label {
  font-family: var(--font-display);
  font-size: 0.82rem;
  font-weight: 600;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: rgba(255,255,255,.8);
  margin-bottom: 0.5rem;
}
.result-value {
  font-size: 2.5rem;
  font-weight: 900;
  font-family: 'Courier New', monospace;
  color: var(--clr-white);
  line-height: 1.3;
  word-break: break-all;
}

/* Details panel */
.result-details {
  background: var(--clr-slate-100);
  border: 1px solid var(--clr-slate-200);
  border-radius: var(--radius-md);
  padding: 1.4rem 1.25rem;
  margin-bottom: 1.25rem;
}
.detail-section {
  margin-bottom: 1.25rem;
}
.detail-section:last-child { margin-bottom: 0; }
.detail-title {
  font-family: var(--font-display);
  font-size: 0.82rem;
  font-weight: 700;
  letter-spacing: 0.07em;
  text-transform: uppercase;
  color: var(--clr-slate-600);
  margin-bottom: 0.75rem;
  display: flex;
  align-items: center;
  gap: 0.4rem;
}
.detail-content {
  font-size: 0.9rem;
  color: var(--clr-slate-600);
  line-height: 1.85;
  font-family: 'Courier New', monospace;
}

/* Step-by-step breakdown items */
.step-item {
  background: var(--clr-white);
  padding: 0.85rem 1rem;
  border-radius: var(--radius-sm);
  margin-bottom: 0.65rem;
  border-left: 3px solid var(--clr-teal);
  font-size: 0.9rem;
  color: var(--clr-slate-600);
  line-height: 1.65;
  box-shadow: var(--shadow-soft);
}
.step-item:last-child { margin-bottom: 0; }
.step-item strong { color: var(--clr-teal-deep); font-weight: 700; }

/* Error */
.result-container .error-box {
  background: #fef2f2;
  border: 2px solid #fecaca;
  border-left: 3px solid #ef4444;
  border-radius: var(--radius-sm);
  padding: 1rem 1.25rem;
  color: #b91c1c;
  font-weight: 600;
  font-size: 0.93rem;
  text-align: center;
}

/* ── Download buttons ── */
.download-buttons {
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem;
}
.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;
}
.info-card strong { color: var(--clr-slate-700); font-weight: 600; }

/* ════════════════════════════════════════
   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;
  border: 1px solid rgba(255,255,255,.04);
}
.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-top: 1.6rem;
  font-size: 0.93rem;
  color: var(--clr-slate-700);
  line-height: 1.7;
}
.highlight-box strong { color: var(--clr-slate-800); font-weight: 600; }

/* ════════════════════════════════════════
   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 code {
  background: var(--clr-slate-100);
  padding: 0.1rem 0.35rem;
  border-radius: 4px;
  font-family: 'Courier New', monospace;
  font-size: 0.86em;
  color: var(--clr-teal-deep);
  border: 1px solid var(--clr-slate-200);
}
.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);
  }
  .operation-grid { grid-template-columns: repeat(2, 1fr); }
  .input-grid { grid-template-columns: 1fr; }
  .op-symbol { padding-top: 0; font-size: 1.75rem; text-align: left; }
  .result-value { font-size: 1.75rem; }

  .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; }
  .form-input { font-size: 1rem; }
  .example-btn { font-size: 0.72rem; }
}

/* ── 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;
}