/* ============================================================
   Basic Calculator — Page Styles
   Inherits: design tokens from index.style.css (loaded via header)
   Unique: 2-column calculator-wrapper, 4-col keypad grid,
           history panel side-by-side, inline FAQ converted to
           standard .faq-section/.faq-item static card style
   ============================================================ */

/* ── 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(2.2rem, 6vw, 3.8rem);
  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: 640px;
  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;
}

/* ════════════════════════════════════════
   2-COLUMN CALCULATOR WRAPPER
   Left: keypad card   Right: history panel
   ════════════════════════════════════════ */
.calculator-wrapper {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1.75rem;
  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); }
}

/* ── Shared card base ── */
.calculator-card,
.history-panel {
  background: var(--clr-white);
  border-radius: var(--radius-lg);
  padding: 2rem;
  box-shadow: var(--shadow-lift);
  border: 1px solid var(--clr-slate-200);
}

/* ── Intro text ── */
.intro-text {
  color: var(--clr-slate-400);
  font-size: 0.88rem;
  line-height: 1.7;
  margin-bottom: 1.5rem;
  padding-bottom: 1.25rem;
  border-bottom: 1px solid var(--clr-slate-200);
}

/* ════════════════════════════════════════
   CALCULATOR DISPLAY
   ════════════════════════════════════════ */
.calculator-display {
  background: var(--clr-slate-900);
  border: 1px solid rgba(13,207,180,.15);
  color: var(--clr-white);
  padding: 1.25rem 1.25rem 1rem;
  border-radius: var(--radius-md);
  margin-bottom: 1.25rem;
  min-height: 6rem;
  display: flex;
  flex-direction: column;
  justify-content: flex-end;
}
.calculator-expression {
  font-family: 'Courier New', monospace;
  font-size: 0.9rem;
  color: rgba(255,255,255,.4);
  margin-bottom: 0.35rem;
  min-height: 1.2rem;
  text-align: right;
  word-break: break-all;
}
.calculator-result {
  font-family: 'Courier New', monospace;
  font-size: 2.4rem;
  font-weight: 700;
  text-align: right;
  color: var(--clr-teal);
  word-break: break-all;
  line-height: 1.1;
}

/* ════════════════════════════════════════
   CALCULATOR BUTTON GRID  (4 columns)
   ════════════════════════════════════════ */
.calculator-buttons {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 0.55rem;
}

/* Base button */
.calc-btn {
  padding: 1.1rem 0.5rem;
  font-family: var(--font-display);
  font-size: 1.2rem;
  font-weight: 700;
  border: none;
  border-radius: var(--radius-sm);
  cursor: pointer;
  transition: all 0.15s ease;
  box-shadow: 0 2px 6px rgba(0,0,0,.08);
  line-height: 1;
  letter-spacing: 0.02em;
}
.calc-btn:hover  { transform: translateY(-2px); box-shadow: 0 4px 12px rgba(0,0,0,.15); }
.calc-btn:active { transform: scale(0.97); }

/* Number — white with slate border */
.calc-btn.number {
  background: var(--clr-white);
  color: var(--clr-slate-800);
  border: 1px solid var(--clr-slate-200);
}
.calc-btn.number:hover { background: var(--clr-slate-100); }

/* Operator — teal */
.calc-btn.operator {
  background: var(--clr-teal-deep);
  color: var(--clr-white);
  border: 1px solid transparent;
}
.calc-btn.operator:hover {
  background: var(--clr-teal);
  color: var(--clr-slate-900);
  box-shadow: var(--shadow-teal);
}

/* Function (⌫ %) — dark slate + teal text */
.calc-btn.function {
  background: #1e293b;
  color: var(--clr-teal);
  border: 1px solid rgba(13,207,180,.2);
  font-size: 1rem;
}
.calc-btn.function:hover {
  background: #0f172a;
  border-color: rgba(13,207,180,.4);
  color: var(--clr-cyan);
}

/* Clear (AC) — red accent */
.calc-btn.clear {
  background: #ef4444;
  color: var(--clr-white);
  border: 1px solid transparent;
}
.calc-btn.clear:hover {
  background: #dc2626;
  box-shadow: 0 4px 12px rgba(239,68,68,.3);
}

/* Equals — green, spans 2 columns */
.calc-btn.equals {
  background: linear-gradient(135deg, #10b981 0%, #059669 100%);
  color: var(--clr-white);
  border: 1px solid transparent;
  grid-column: span 2;
  font-size: 1.4rem;
}
.calc-btn.equals:hover {
  background: linear-gradient(135deg, #059669 0%, #047857 100%);
  box-shadow: 0 6px 18px rgba(16,185,129,.4);
}

/* Zero spans 2 columns */
.calc-btn.span-2 { grid-column: span 2; }

/* ════════════════════════════════════════
   HISTORY PANEL
   ════════════════════════════════════════ */
.history-panel {
  max-height: 700px;
  display: flex;
  flex-direction: column;
}
.history-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 1.25rem;
  padding-bottom: 1rem;
  border-bottom: 1px solid var(--clr-slate-200);
  flex-shrink: 0;
}
.history-title {
  font-family: var(--font-display);
  font-size: 1rem;
  font-weight: 700;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--clr-slate-700);
}
.history-actions {
  display: flex;
  gap: 0.45rem;
  flex-wrap: wrap;
}
.history-btn {
  padding: 0.35rem 0.75rem;
  background: transparent;
  color: var(--clr-teal);
  border: 1px solid rgba(13,207,180,.35);
  border-radius: var(--radius-pill);
  font-family: var(--font-display);
  font-weight: 600;
  font-size: 0.75rem;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  cursor: pointer;
  transition: all var(--transition);
  white-space: nowrap;
}
.history-btn:hover {
  background: rgba(13,207,180,.1);
  border-color: var(--clr-teal);
  transform: translateY(-1px);
}

.history-list {
  flex: 1;
  overflow-y: auto;
  padding-right: 0.35rem;
}
.history-list::-webkit-scrollbar { width: 4px; }
.history-list::-webkit-scrollbar-track { background: transparent; }
.history-list::-webkit-scrollbar-thumb { background: rgba(13,207,180,.3); border-radius: 2px; }

.history-empty {
  text-align: center;
  color: var(--clr-slate-300);
  padding: 2.5rem 1rem;
  font-size: 0.88rem;
  font-style: italic;
}
.history-item {
  background: var(--clr-slate-100);
  padding: 0.8rem 0.95rem;
  border-radius: var(--radius-sm);
  margin-bottom: 0.6rem;
  border: 1px solid var(--clr-slate-200);
  border-left: 3px solid var(--clr-teal);
  transition: all var(--transition);
  animation: slideInRight 0.25s ease both;
}
@keyframes slideInRight {
  from { opacity: 0; transform: translateX(-12px); }
  to   { opacity: 1; transform: translateX(0); }
}
.history-item:hover {
  background: var(--clr-white);
  transform: translateX(3px);
  box-shadow: var(--shadow-soft);
}
.history-item:last-child { margin-bottom: 0; }

.history-expression {
  font-family: 'Courier New', monospace;
  font-size: 0.82rem;
  color: var(--clr-slate-400);
  margin-bottom: 0.2rem;
}
.history-result {
  font-family: 'Courier New', monospace;
  font-size: 1.05rem;
  font-weight: 700;
  color: var(--clr-teal-deep);
}
.history-time {
  font-size: 0.7rem;
  color: var(--clr-slate-300);
  margin-top: 0.2rem;
}

/* ════════════════════════════════════════
   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: 1.5rem;
  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: 0.65rem;
}
.info-card p {
  font-size: 0.875rem;
  color: var(--clr-slate-400);
  line-height: 1.65;
}
.info-card a {
  color: var(--clr-teal-deep);
  text-decoration: underline;
  text-underline-offset: 2px;
}

/* ════════════════════════════════════════
   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: 1.8;
}
.blog-content h2 {
  font-family: var(--font-display);
  font-size: clamp(1.6rem, 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: 1rem;
}
.blog-content h4 {
  font-family: var(--font-display);
  font-size: 1rem;
  font-weight: 700;
  letter-spacing: 0.05em;
  text-transform: uppercase;
  color: var(--clr-teal-deep);
  margin-top: 2rem;
  margin-bottom: 0.75rem;
}
.blog-content p {
  color: var(--clr-slate-600);
  font-size: 0.975rem;
  margin-bottom: 1.25rem;
  line-height: 1.85;
}
.blog-content ul,
.blog-content ol {
  color: var(--clr-slate-600);
  margin-left: 1.5rem;
  margin-bottom: 1.5rem;
}
.blog-content li {
  margin-bottom: 0.65rem;
  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; }

.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: 1.25rem 1.35rem;
  border-radius: var(--radius-sm);
  margin: 1.75rem 0;
  font-size: 0.93rem;
  color: var(--clr-slate-700);
  line-height: 1.7;
}
.formula-box {
  background: var(--clr-slate-900);
  color: var(--clr-teal);
  padding: 1.1rem 1.35rem;
  border-radius: var(--radius-sm);
  font-family: 'Courier New', monospace;
  font-size: 0.85rem;
  margin: 1.25rem 0;
  overflow-x: auto;
  border: 1px solid rgba(13,207,180,.2);
  letter-spacing: 0.02em;
  line-height: 1.9;
  white-space: pre-wrap;
}

/* ════════════════════════════════════════
   FAQ SECTION  — standard static card style
   (matching statistics-calculator & logarithm-calculator)
   ════════════════════════════════════════ */
.faq-section {
  margin-top: 2.5rem;
}
.faq-section > 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-bottom: 1.25rem;
}
.faq-item {
  border-left: 3px solid var(--clr-teal);
  padding: 1rem 1.2rem;
  margin-bottom: 1rem;
  background: var(--clr-slate-100);
  border-radius: var(--radius-sm);
}
.faq-item h4 {
  font-family: var(--font-display);
  font-size: 0.88rem;
  font-weight: 700;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  color: var(--clr-slate-800);
  margin-top: 0;
  margin-bottom: 0.4rem;
}
.faq-item p {
  margin: 0;
  font-size: 0.88rem;
  color: var(--clr-slate-400);
  line-height: 1.7;
}
.faq-item a {
  color: var(--clr-teal-deep);
  text-decoration: underline;
  text-underline-offset: 2px;
}

/* ════════════════════════════════════════
   RESPONSIVE
   ════════════════════════════════════════ */
@media (max-width: 968px) {
  .calculator-wrapper { grid-template-columns: 1fr; }
  .history-panel { max-height: 480px; }
}

@media (max-width: 768px) {
  .page-header { padding: 3rem 1.25rem 4rem; }
  .page-header h1 { font-size: 2rem; }
  .page-header p { font-size: 0.95rem; }

  .calculator-wrapper { margin-top: -1.5rem; gap: 1.25rem; }
  .calculator-card,
  .history-panel { padding: 1.25rem; border-radius: var(--radius-md); }

  .calculator-result { font-size: 1.9rem; }
  .calc-btn { padding: 0.9rem 0.4rem; font-size: 1rem; }
  .calc-btn.equals { font-size: 1.2rem; }

  .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; }

  .info-grid { grid-template-columns: 1fr; }
}

@media (max-width: 480px) {
  .calc-page-wrap { padding: 0 0.75rem; }
  .calc-btn { padding: 0.75rem 0.2rem; font-size: 0.9rem; border-radius: 6px; }
  .history-actions { gap: 0.3rem; }
  .history-btn { font-size: 0.7rem; padding: 0.3rem 0.55rem; }
}

/* ── 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;
}