/* ============================================================
   Algebra Calculator — Page Styles
   Inherits: design tokens from index.style.css
   Unique: 4-mode operation-grid (operation-btn/icon/sub),
           dynamically-injected input-section (input-field in
           Courier New, example-btn in Courier New),
           hero-result with large monospace value,
           coeff-details + discriminant-note (quadratic only),
           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 ── */
.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);
}

/* ════════════════════════════════════════
   4-MODE OPERATION GRID
   Large clickable operation cards
   ════════════════════════════════════════ */
.operation-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 1rem;
  margin-bottom: 2rem;
}
.operation-btn {
  padding: 1.25rem 1.15rem;
  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);
  user-select: none;
}
.operation-btn:hover {
  background: var(--clr-teal-glow);
  border-color: rgba(13,207,180,.4);
  transform: translateY(-2px);
  color: var(--clr-teal-deep);
}
.operation-btn.active {
  background: var(--clr-teal-deep);
  border-color: var(--clr-teal-deep);
  color: var(--clr-white);
  box-shadow: var(--shadow-teal);
}
.operation-icon {
  font-size: 2rem;
  display: block;
  margin-bottom: 0.35rem;
  line-height: 1;
}
/* mode title — uses font-body (Inter) matching source */
.operation-btn > div:nth-child(2) {
  font-family: var(--font-display);
  font-size: 0.95rem;
  font-weight: 700;
  letter-spacing: 0.03em;
  text-transform: uppercase;
  margin-bottom: 0.2rem;
}
.operation-sub {
  font-size: 0.8rem;
  opacity: 0.85;
  margin-top: 0.15rem;
  font-family: 'Courier New', monospace;
  letter-spacing: 0.02em;
}

/* ════════════════════════════════════════
   DYNAMICALLY INJECTED INPUT SECTION
   (Injected by selectOperation() into #input-section)
   ════════════════════════════════════════ */
.input-group {
  margin-bottom: 1.5rem;
}
.input-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;
}

/* Monospace equation input — key: Courier New like source */
.input-field {
  width: 100%;
  padding: 0.95rem 1rem;
  border: 2px solid var(--clr-slate-200);
  border-radius: var(--radius-sm);
  font-size: 1rem;
  font-family: 'Courier New', monospace;
  color: var(--clr-slate-800);
  background: var(--clr-slate-100);
  transition: all var(--transition);
  box-sizing: border-box;
}
.input-field:focus {
  outline: none;
  border-color: var(--clr-teal);
  background: var(--clr-white);
  box-shadow: 0 0 0 3px var(--clr-teal-glow);
}
.input-field::placeholder {
  color: var(--clr-slate-300);
  font-size: 0.9rem;
}

/* Example equation chip buttons — Courier New */
.example-buttons {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
  margin-top: 0.75rem;
}
.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);
}
.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: 1.9rem;
  padding: 1.75rem 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;
}
.results-section.show { display: block; }

.result-title {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  font-family: var(--font-display);
  font-size: 0.85rem;
  font-weight: 700;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--clr-slate-600);
  margin-bottom: 1.15rem;
}

/* ── Hero result: large centered answer ── */
.hero-result {
  background: var(--clr-teal-deep);
  border-radius: var(--radius-md);
  padding: 1.3rem 1.15rem;
  text-align: center;
  color: var(--clr-white);
  margin-bottom: 1.5rem;
}
.hero-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: 0.4rem;
}
.hero-result-value {
  font-size: 2rem;
  font-weight: 900;
  font-family: 'Courier New', monospace; /* monospace — matches source exactly */
  color: var(--clr-white);
  line-height: 1.3;
  letter-spacing: 0.01em;
}

/* ── Generic result box ── */
.result-box {
  background: var(--clr-white);
  border-radius: var(--radius-sm);
  padding: 1rem 1rem 0.9rem;
  box-shadow: var(--shadow-soft);
  border: 1px solid var(--clr-slate-200);
  margin-bottom: 1rem;
}
.result-box:last-child { margin-bottom: 0; }

.result-label {
  font-family: var(--font-display);
  font-size: 0.8rem;
  font-weight: 700;
  letter-spacing: 0.07em;
  text-transform: uppercase;
  color: var(--clr-slate-500);
  margin-bottom: 0.35rem;
}
/* result-value uses Courier New matching source */
.result-value {
  font-size: 1.05rem;
  font-weight: 700;
  color: var(--clr-teal-deep);
  font-family: 'Courier New', monospace;
  word-break: break-all;
}

/* Error box */
.result-box.error-box { border-left: 3px solid #ef4444; }
.error-label { color: #b91c1c; }
.error-message { font-size: 0.93rem; color: #b91c1c; font-weight: 500; }

/* ── Quadratic-specific ── */
.coeff-details {
  font-family: 'Courier New', monospace;
  color: var(--clr-slate-600);
  font-size: 0.93rem;
  line-height: 1.75;
  margin-top: 0.5rem;
}
.discriminant-note {
  margin-top: 0.45rem;
  font-size: 0.86rem;
  color: var(--clr-slate-500);
  font-style: italic;
}

/* ── Step-by-step panel ── */
.step-by-step {
  background: #111827;
  color: #e5e7eb;
  padding: 0.9rem 1rem;
  border-radius: var(--radius-sm);
  font-family: 'Courier New', monospace;
  font-size: 0.85rem;
  line-height: 1.75;
  max-height: 420px;
  overflow-y: auto;
  border: 1px solid rgba(13,207,180,.1);
}
.step-by-step::-webkit-scrollbar { width: 4px; }
.step-by-step::-webkit-scrollbar-track { background: transparent; }
.step-by-step::-webkit-scrollbar-thumb { background: rgba(96,165,250,.3); border-radius: 2px; }

.step {
  position: relative;
  padding-left: 1.2rem;
  margin-bottom: 0.45rem;
  color: #e5e7eb;
}
.step:last-child { margin-bottom: 0; }
.step::before {
  content: '→';
  position: absolute;
  left: 0;
  top: 0;
  color: #60a5fa; /* blue — matches source exactly */
  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;
}
.info-card code {
  background: var(--clr-slate-100);
  padding: 0.1rem 0.35rem;
  border-radius: 4px;
  font-family: 'Courier New', monospace;
  font-size: 0.85em;
  color: var(--clr-teal-deep);
  border: 1px solid var(--clr-slate-200);
}
.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 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; }

/* formula-box: Courier New, dark bg — unique: contains <p> tags */
.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: 1.7;
  overflow-x: auto;
  border: 1px solid rgba(255,255,255,.04);
}
.formula-box p {
  color: #e5e7eb;
  margin-bottom: 0.45rem;
  font-size: 0.9rem;
  line-height: 1.7;
}
.formula-box p:last-child { margin-bottom: 0; }
.formula-box strong { color: var(--clr-teal); -webkit-text-fill-color: var(--clr-teal); font-weight: 700; }
.formula-box code {
  color: #38bdf8;
  background: transparent;
  font-size: inherit;
}
.formula-box ul {
  margin-left: 1.25rem;
  margin-bottom: 0.35rem;
  padding: 0;
  color: #e5e7eb;
}
.formula-box li { margin-bottom: 0.2rem; font-size: 0.9rem; line-height: 1.65; }

/* 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; }

/* blog inline code */
.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);
}

/* ════════════════════════════════════════
   FAQ SECTION — static .faq-item with
   border-top separator pattern
   (same as standard-deviation-calculator)
   ════════════════════════════════════════ */
.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: 1fr; }
  .hero-result-value { font-size: 1.7rem; }

  .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; }
  .input-field { font-size: 0.9rem; }
  .example-btn { font-size: 0.72rem; }
  .step-by-step { font-size: 0.78rem; }
}

/* ── 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;
}