/* ============================================
   PROPORTION CALCULATOR — page-specific styles
   Accent: violet (#a78bfa dark / #7c3aed light) — Math category
   Inherits variables from css/styles.css
   ============================================ */

/* ---- Page wrapper ---- */
.calc-page {
  position: relative; z-index: 1;
  max-width: 1380px; margin: 0 auto;
  padding: 48px 24px 80px;
  display: grid;
  grid-template-columns: 1fr 480px;
  grid-template-rows: auto auto;
  gap: 48px; align-items: start;
}
.calc-page-info {
  position: static;
}

/* ---- Breadcrumb ---- */
.calc-breadcrumb {
  display: flex; align-items: center; gap: 8px;
  font-size: 13px; color: var(--text-dim); margin-bottom: 20px; flex-wrap: wrap;
}
.calc-breadcrumb a { color: var(--text-dim); transition: color var(--transition); }
.calc-breadcrumb a:hover { color: #a78bfa; }
.calc-breadcrumb i { font-size: 10px; }

/* ---- Category tag — violet for Math ---- */
.calc-page-tag {
  display: inline-flex; align-items: center; gap: 7px;
  padding: 4px 12px 4px 8px;
  background: rgba(167,139,250,0.10); border: 1px solid rgba(167,139,250,0.28);
  border-radius: 100px; font-size: 12px; font-weight: 600; color: #a78bfa;
  text-transform: uppercase; letter-spacing: 0.08em; margin-bottom: 18px;
}
body.light-theme .calc-page-tag {
  background: rgba(124,58,237,0.07); border-color: rgba(124,58,237,0.22); color: #7c3aed;
}

/* ---- Page title ---- */
.calc-page-title {
  font-family: 'Bricolage Grotesque', sans-serif;
  font-size: clamp(28px, 3.2vw, 44px); font-weight: 800;
  line-height: 1.1; letter-spacing: -1.5px; color: var(--text); margin-bottom: 16px;
}
.calc-page-title span { color: #a78bfa; }
body.light-theme .calc-page-title span { color: #7c3aed; }

.calc-page-desc { font-size: 16px; line-height: 1.75; color: var(--text-muted); margin-bottom: 32px; }

/* ---- Feature pills ---- */
.calc-features { display: flex; flex-wrap: wrap; gap: 8px; margin-bottom: 40px; }
.calc-feature-pill {
  display: inline-flex; align-items: center; gap: 6px; padding: 6px 12px;
  background: var(--surface); border: 1px solid var(--border); border-radius: 100px;
  font-size: 13px; font-weight: 500; color: var(--text-muted);
}
.calc-feature-pill i { color: #a78bfa; font-size: 12px; }
body.light-theme .calc-feature-pill i { color: #7c3aed; }

/* ---- Content blocks ---- */
.calc-page-content {
  margin-top: 0;
  min-width: 0;
}

.calc-page-content.fade-up {
  opacity: 1;
  transform: none;
  animation: none;
  transition: none;
  visibility: visible;
}
.content-block { margin-bottom: 40px; }
.content-block h2 {
  font-family: 'Bricolage Grotesque', sans-serif; font-size: 22px; font-weight: 700;
  letter-spacing: -0.5px; color: var(--text); margin-bottom: 14px;
}
.content-block p { font-size: 15px; line-height: 1.8; color: var(--text-muted); margin-bottom: 10px; }
.content-block strong { color: var(--text); font-weight: 600; }

/* ============================================
   FORMULA BOX (SEO section)
   ============================================ */
.prop-formula-box {
  background: var(--bg-2); border: 1px solid var(--border);
  border-left: 3px solid #a78bfa; border-radius: var(--radius-sm);
  overflow: hidden; margin-bottom: 22px;
}
body.light-theme .prop-formula-box { border-left-color: #7c3aed; }
.prop-formula-title {
  display: flex; align-items: center; gap: 8px; padding: 10px 16px;
  background: var(--bg-3); border-bottom: 1px solid var(--border);
  font-size: 11px; font-weight: 700; text-transform: uppercase; letter-spacing: 0.08em; color: #a78bfa;
}
body.light-theme .prop-formula-title { color: #7c3aed; }
.prop-formula-display {
  display: flex; align-items: center; flex-wrap: wrap; gap: 16px;
  padding: 16px 20px; font-family: 'Bricolage Grotesque', sans-serif;
}
.prop-frac {
  display: flex; flex-direction: column; align-items: center; gap: 3px;
}
.prop-num, .prop-den {
  font-size: 18px; font-weight: 700; color: #a78bfa; line-height: 1;
}
body.light-theme .prop-num, body.light-theme .prop-den { color: #7c3aed; }
.prop-bar { width: 100%; min-width: 24px; height: 2px; background: var(--text-muted); border-radius: 2px; }
.prop-eq, .prop-arrow { font-size: 20px; font-weight: 700; color: var(--text-muted); }
.prop-cross { font-family: 'DM Mono', monospace; font-size: 14px; font-weight: 600; color: var(--text); }
.prop-formula-vars {
  padding: 0 20px 14px; display: grid; grid-template-columns: 1fr 1fr; gap: 6px;
}
.prop-var-row { display: flex; align-items: center; gap: 8px; font-size: 13px; color: var(--text-muted); }
.prop-var { font-family: 'DM Mono', monospace; font-size: 13px; font-weight: 700; color: #a78bfa; min-width: 16px; }
body.light-theme .prop-var { color: #7c3aed; }

/* ============================================
   SOLVE CARDS (4-mode grid)
   ============================================ */
.prop-solve-grid {
  display: grid; grid-template-columns: 1fr 1fr; gap: 10px; margin-top: 4px;
}
.prop-solve-card {
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius-sm);
  padding: 12px 14px; display: flex; flex-direction: column; gap: 5px;
  transition: border-color var(--transition), box-shadow var(--transition);
}
.prop-solve-card:hover { border-color: rgba(167,139,250,0.4); box-shadow: var(--shadow); }
body.light-theme .prop-solve-card:hover { border-color: rgba(124,58,237,0.3); }
.prop-solve-label {
  font-size: 11px; font-weight: 700; text-transform: uppercase; letter-spacing: 0.07em; color: #a78bfa;
}
body.light-theme .prop-solve-label { color: #7c3aed; }
.prop-solve-formula { font-family: 'DM Mono', monospace; font-size: 13px; font-weight: 600; color: var(--text); }
.prop-solve-example { font-size: 12px; color: var(--text-dim); line-height: 1.5; }
.prop-solve-example strong { color: #a78bfa; }
body.light-theme .prop-solve-example strong { color: #7c3aed; }

/* ============================================
   APPLICATION CARDS
   ============================================ */
.prop-app-grid {
  display: grid; grid-template-columns: 1fr 1fr; gap: 12px; margin-top: 16px;
}
.prop-app-card {
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius-sm);
  padding: 14px; display: flex; gap: 12px; align-items: flex-start;
  transition: border-color var(--transition), box-shadow var(--transition);
}
.prop-app-card:hover { border-color: rgba(167,139,250,0.4); box-shadow: var(--shadow); }
.prop-app-icon {
  flex-shrink: 0; width: 34px; height: 34px; border-radius: 8px;
  background: rgba(167,139,250,0.10); border: 1px solid rgba(167,139,250,0.24);
  display: flex; align-items: center; justify-content: center;
  font-size: 14px; color: #a78bfa;
}
body.light-theme .prop-app-icon { background: rgba(124,58,237,0.07); border-color: rgba(124,58,237,0.2); color: #7c3aed; }
.prop-app-body { display: flex; flex-direction: column; gap: 4px; }
.prop-app-body strong { font-size: 13px; font-weight: 700; color: var(--text); }
.prop-app-body span   { font-size: 12px; line-height: 1.6; color: var(--text-muted); }

/* ---- FAQ ---- */
.faq-list { display: flex; flex-direction: column; gap: 8px; }
.faq-item { background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius-sm); overflow: hidden; }
.faq-item:hover { border-color: var(--border-hover); }
.faq-question {
  width: 100%; display: flex; align-items: center; justify-content: space-between; gap: 12px;
  padding: 14px 18px; background: transparent; border: none; cursor: pointer;
  font-family: 'DM Sans', sans-serif; font-size: 15px; font-weight: 600;
  color: var(--text); text-align: left; transition: color var(--transition);
}
.faq-question:hover { color: #a78bfa; }
body.light-theme .faq-question:hover { color: #7c3aed; }
.faq-question i { font-size: 12px; color: var(--text-dim); flex-shrink: 0; transition: transform var(--transition), color var(--transition); }
.faq-item.open .faq-question i { transform: rotate(180deg); color: #a78bfa; }
body.light-theme .faq-item.open .faq-question i { color: #7c3aed; }
.faq-answer { max-height: 0; overflow: hidden; transition: max-height 0.35s ease, padding 0.35s ease; font-size: 14px; line-height: 1.75; color: var(--text-muted); padding: 0 18px; }
.faq-item.open .faq-answer { max-height: 500px; padding: 0 18px 16px; }

/* ---- Also search chips ---- */
.also-search-grid { display: flex; flex-wrap: wrap; gap: 10px; margin-top: 16px; }
.also-search-chip {
  display: inline-flex; align-items: center; gap: 8px; padding: 8px 14px;
  background: var(--surface); border: 1px solid var(--border); border-radius: 100px;
  font-size: 13px; font-weight: 500; color: var(--text-muted); white-space: nowrap;
  transition: background var(--transition), border-color var(--transition), color var(--transition);
}
.also-search-chip:hover { background: rgba(167,139,250,0.1); border-color: #a78bfa; color: #a78bfa; }
body.light-theme .also-search-chip:hover { background: rgba(124,58,237,0.07); border-color: #7c3aed; color: #7c3aed; }

/* ============================================
   CALC CARD — 480px
   ============================================ */
.calc-panel { position: sticky; top: calc(var(--header-h) + 24px); }
.calc-card {
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius-lg);
  overflow: hidden; box-shadow: var(--shadow-lg), 0 0 60px rgba(167,139,250,0.07);
}
.calc-card-header {
  padding: 20px 24px 18px; background: var(--bg-2); border-bottom: 1px solid var(--border);
  display: none; align-items: center; gap: 12px;
}
@media (max-width: 1024px) { .calc-card-header { display: flex; } }
.calc-card-icon {
  width: 40px; height: 40px; border-radius: 10px;
  background: rgba(167,139,250,0.10); border: 1px solid rgba(167,139,250,0.26);
  display: flex; align-items: center; justify-content: center;
  font-size: 18px; color: #a78bfa; flex-shrink: 0;
}
body.light-theme .calc-card-icon { background: rgba(124,58,237,0.07); border-color: rgba(124,58,237,0.22); color: #7c3aed; }
.calc-card-header-text h3 { font-family: 'Bricolage Grotesque', sans-serif; font-size: 16px; font-weight: 700; color: var(--text); margin-bottom: 2px; }
.calc-card-header-text p  { font-size: 12px; color: var(--text-dim); }
.calc-card-body { padding: 20px 22px 22px; }

/* ============================================
   PRESETS STRIP
   ============================================ */
.prop-presets { margin-bottom: 16px; }
.prop-presets-label {
  font-size: 11px; font-weight: 700; text-transform: uppercase; letter-spacing: 0.07em;
  color: var(--text-dim); margin-bottom: 8px;
}
.prop-presets-row { display: flex; gap: 6px; flex-wrap: wrap; }
.prop-preset-btn {
  flex: 1; min-width: 56px; display: flex; flex-direction: column; align-items: center; gap: 4px;
  padding: 8px 6px; background: var(--bg-2); border: 1px solid var(--border);
  border-radius: var(--radius-sm); cursor: pointer; font-family: 'DM Sans', sans-serif;
  font-size: 11px; font-weight: 600; color: var(--text-dim);
  transition: background var(--transition), border-color var(--transition), color var(--transition);
}
.prop-preset-btn i { font-size: 14px; }
.prop-preset-btn:hover { background: rgba(167,139,250,0.1); border-color: rgba(167,139,250,0.4); color: #a78bfa; }
body.light-theme .prop-preset-btn:hover { background: rgba(124,58,237,0.07); border-color: rgba(124,58,237,0.28); color: #7c3aed; }
.prop-preset-btn.active { background: rgba(167,139,250,0.12); border-color: #a78bfa; color: #a78bfa; }
body.light-theme .prop-preset-btn.active { background: rgba(124,58,237,0.08); border-color: #7c3aed; color: #7c3aed; }

/* ============================================
   VISUAL EQUATION PANEL  A/B = C/D
   ============================================ */
.prop-equation-panel {
  display: flex; align-items: stretch; gap: 12px; margin-bottom: 12px;
}
.prop-fraction-box {
  flex: 1; background: var(--bg-2); border: 1px solid var(--border);
  border-radius: var(--radius-sm); display: flex; flex-direction: column;
  overflow: hidden; transition: border-color var(--transition), box-shadow var(--transition);
}
.prop-fraction-box:focus-within {
  border-color: #a78bfa; box-shadow: 0 0 0 3px rgba(167,139,250,0.15);
}
body.light-theme .prop-fraction-box:focus-within { border-color: #7c3aed; box-shadow: 0 0 0 3px rgba(124,58,237,0.10); }
.prop-fraction-box.has-unknown { border-color: rgba(167,139,250,0.5); background: rgba(167,139,250,0.04); }
body.light-theme .prop-fraction-box.has-unknown { border-color: rgba(124,58,237,0.35); background: rgba(124,58,237,0.03); }
.prop-frac-field-wrap { flex: 1; display: flex; align-items: center; }
.prop-frac-input {
  width: 100%; padding: 12px 14px; background: transparent; border: none; outline: none;
  font-family: 'Bricolage Grotesque', sans-serif; font-size: 24px; font-weight: 800;
  color: var(--text); text-align: center; -moz-appearance: textfield; appearance: none;
  transition: color var(--transition);
}
.prop-frac-input::-webkit-outer-spin-button,
.prop-frac-input::-webkit-inner-spin-button { -webkit-appearance: none; margin: 0; }
.prop-frac-input::placeholder { color: var(--text-dim); font-weight: 700; opacity: 0.6; }
.prop-frac-input.is-unknown { color: #a78bfa; }
body.light-theme .prop-frac-input.is-unknown { color: #7c3aed; }
.prop-frac-divider { height: 2px; background: var(--border); margin: 0 12px; }
.prop-fraction-box:focus-within .prop-frac-divider { background: rgba(167,139,250,0.5); }

/* Equals sign between fractions */
.prop-equals-sign {
  flex-shrink: 0; display: flex; align-items: center; justify-content: center;
  width: 40px;
  font-family: 'Bricolage Grotesque', sans-serif; font-size: 28px; font-weight: 800;
  color: var(--text-dim); user-select: none;
  transition: color var(--transition), transform var(--transition);
}
.prop-equals-sign.valid   { color: #34d399; transform: scale(1.1); }
.prop-equals-sign.invalid { color: var(--pink); transform: scale(1.1); }
body.light-theme .prop-equals-sign.valid   { color: #059669; }
body.light-theme .prop-equals-sign.invalid { color: #e11d48; }

/* Hint line */
.prop-hint {
  display: flex; align-items: center; gap: 7px; padding: 8px 12px;
  background: var(--bg-3); border: 1px solid var(--border); border-radius: var(--radius-sm);
  font-size: 12px; color: var(--text-dim); margin-bottom: 14px;
}
.prop-hint i { color: #a78bfa; flex-shrink: 0; }
body.light-theme .prop-hint i { color: #7c3aed; }

/* Buttons */
.calc-btn-primary {
  display: flex; align-items: center; justify-content: center; gap: 10px;
  width: 100%; padding: 14px 20px; background: var(--accent); color: #0c0f1a;
  font-family: 'Bricolage Grotesque', sans-serif; font-size: 16px; font-weight: 700;
  border: none; border-radius: var(--radius-sm); cursor: pointer; margin-bottom: 8px;
  transition: opacity var(--transition), transform var(--transition), box-shadow var(--transition);
  position: relative; overflow: hidden;
}
body.light-theme .calc-btn-primary { color: #fff; }
.calc-btn-primary::after { content: ''; position: absolute; inset: 0; background: #000; opacity: 0; transition: opacity 0.15s; }
.calc-btn-primary:hover { box-shadow: 0 4px 20px var(--accent-glow); }
.calc-btn-primary:hover::after { opacity: 0.06; }
.calc-btn-primary:active { transform: scale(0.98); }

.prop-clear-btn {
  display: flex; align-items: center; justify-content: center; gap: 8px;
  width: 100%; padding: 9px 16px;
  background: transparent; border: 1px solid var(--border); border-radius: var(--radius-sm);
  color: var(--text-dim); font-family: 'DM Sans', sans-serif; font-size: 13px; font-weight: 600;
  cursor: pointer; margin-bottom: 10px;
  transition: background var(--transition), border-color var(--transition), color var(--transition);
}
.prop-clear-btn:hover { background: var(--bg-3); border-color: var(--border-hover); color: var(--text); }

/* Error toast */
.calc-error {
  display: flex; align-items: center; gap: 10px; padding: 12px 16px;
  background: var(--pink-dim); border: 1px solid rgba(251,113,133,0.3);
  border-radius: var(--radius-sm); color: var(--pink); font-size: 14px; font-weight: 500;
  margin-bottom: 4px; opacity: 0; transform: translateY(-6px);
  transition: opacity 0.3s ease, transform 0.3s ease; pointer-events: none;
}
.calc-error.show { opacity: 1; transform: translateY(0); pointer-events: auto; }

/* ============================================
   RESULT CARD
   ============================================ */
.result-card {
  margin-top: 14px; background: var(--bg-2); border: 1px solid var(--border);
  border-radius: var(--radius); overflow: hidden;
  display: none; opacity: 0; transform: translateY(8px);
  transition: opacity 0.4s ease, transform 0.4s ease;
}
.result-card.show { display: block; opacity: 1; transform: translateY(0); }

.result-hero {
  padding: 18px 22px 16px;
  background: linear-gradient(135deg, rgba(167,139,250,0.08) 0%, transparent 60%);
  border-bottom: 1px solid var(--border);
  display: flex; flex-direction: column; gap: 5px;
}
.result-hero-label { font-size: 11px; font-weight: 700; text-transform: uppercase; letter-spacing: 0.1em; color: #a78bfa; }
body.light-theme .result-hero-label { color: #7c3aed; }
.prop-result-answer {
  font-family: 'Bricolage Grotesque', sans-serif;
  font-size: 36px; font-weight: 800; letter-spacing: -1.2px; color: var(--text); line-height: 1.1;
}
.result-hero-sub { font-size: 14px; color: var(--text-muted); }

/* ---- Simplified ratio row ---- */
.prop-simplified-row {
  display: flex; align-items: center; gap: 0; background: var(--surface);
  border-bottom: 1px solid var(--border);
}
.prop-simplified-block {
  flex: 1; padding: 12px 16px; display: flex; flex-direction: column; gap: 3px;
}
.prop-simplified-block:first-child { border-right: 1px solid var(--border); }
.prop-simplified-label { font-size: 10px; text-transform: uppercase; letter-spacing: 0.07em; color: var(--text-dim); font-weight: 600; }
.prop-simplified-val  { font-family: 'Bricolage Grotesque', sans-serif; font-size: 18px; font-weight: 800; color: var(--text); }
.prop-simplified-eq {
  flex-shrink: 0; padding: 0 12px;
  font-family: 'Bricolage Grotesque', sans-serif; font-size: 18px; font-weight: 800; color: var(--text-dim);
}

/* ---- Step-by-step section ---- */
.prop-steps-section {
  background: var(--bg-2); border-bottom: 1px solid var(--border); padding: 14px 18px 16px;
}
.prop-steps-title {
  display: flex; align-items: center; gap: 8px; margin-bottom: 12px;
  font-size: 11px; font-weight: 700; text-transform: uppercase; letter-spacing: 0.08em; color: #a78bfa;
}
body.light-theme .prop-steps-title { color: #7c3aed; }
.prop-steps-list { display: flex; flex-direction: column; gap: 8px; }
.prop-step {
  display: flex; gap: 12px; align-items: flex-start;
}
.prop-step-num {
  flex-shrink: 0; width: 22px; height: 22px; border-radius: 50%;
  background: rgba(167,139,250,0.12); border: 1px solid rgba(167,139,250,0.28);
  display: flex; align-items: center; justify-content: center;
  font-family: 'DM Mono', monospace; font-size: 11px; font-weight: 700; color: #a78bfa;
  margin-top: 1px;
}
body.light-theme .prop-step-num { background: rgba(124,58,237,0.07); border-color: rgba(124,58,237,0.22); color: #7c3aed; }
.prop-step-text { font-size: 13px; line-height: 1.65; color: var(--text-muted); }
.prop-step-text strong { color: var(--text); font-weight: 700; font-family: 'DM Mono', monospace; }
.prop-step-text .prop-step-hl { color: #a78bfa; font-weight: 700; }
body.light-theme .prop-step-text .prop-step-hl { color: #7c3aed; }

/* Result note */
.result-note {
  display: flex; align-items: flex-start; gap: 8px;
  padding: 10px 18px; font-size: 12px; color: var(--text-dim); background: var(--surface);
}
.result-note i { color: #a78bfa; font-size: 11px; flex-shrink: 0; margin-top: 2px; }
body.light-theme .result-note i { color: #7c3aed; }

/* ============================================
   TOPIC CLUSTER
   ============================================ */
.topic-cluster-section {
  position: relative; z-index: 1;
  background: var(--bg-2); border-top: 1px solid var(--border); border-bottom: 1px solid var(--border);
}
.topic-cluster-inner { max-width: 1380px; margin: 0 auto; padding: 56px 24px; }
.topic-cluster-header { max-width: 680px; margin-bottom: 40px; }
.topic-cluster-tag {
  display: inline-flex; align-items: center; gap: 7px; padding: 4px 12px 4px 8px;
  background: rgba(167,139,250,0.10); border: 1px solid rgba(167,139,250,0.24);
  border-radius: 100px; font-size: 12px; font-weight: 600; color: #a78bfa;
  text-transform: uppercase; letter-spacing: 0.08em; margin-bottom: 16px;
}
body.light-theme .topic-cluster-tag { background: rgba(124,58,237,0.07); border-color: rgba(124,58,237,0.2); color: #7c3aed; }
.topic-cluster-header h2 { font-family: 'Bricolage Grotesque', sans-serif; font-size: clamp(22px,2.5vw,30px); font-weight: 800; letter-spacing: -0.8px; color: var(--text); margin-bottom: 12px; }
.topic-cluster-header p { font-size: 15px; line-height: 1.75; color: var(--text-muted); }
.cluster-grid { display: grid; grid-template-columns: 280px 1fr; gap: 24px; margin-bottom: 40px; align-items: start; }
.cluster-primary { background: var(--surface); border: 2px solid #a78bfa; border-radius: var(--radius); padding: 22px; position: relative; }
body.light-theme .cluster-primary { border-color: #7c3aed; }
.cluster-primary::before { content: ''; position: absolute; inset: 0; border-radius: inherit; background: linear-gradient(135deg, rgba(167,139,250,0.07) 0%, transparent 60%); pointer-events: none; }
.cluster-primary-label { display: inline-flex; align-items: center; gap: 6px; font-size: 11px; font-weight: 700; text-transform: uppercase; letter-spacing: 0.08em; color: #a78bfa; margin-bottom: 10px; }
body.light-theme .cluster-primary-label { color: #7c3aed; }
.cluster-primary h3 { font-family: 'Bricolage Grotesque', sans-serif; font-size: 18px; font-weight: 700; color: var(--text); margin-bottom: 8px; position: relative; }
.cluster-primary p  { font-size: 13px; line-height: 1.65; color: var(--text-muted); margin-bottom: 14px; position: relative; }
.cluster-keywords { display: flex; flex-wrap: wrap; gap: 6px; position: relative; }
.cluster-keywords span { padding: 3px 9px; background: rgba(167,139,250,0.10); border: 1px solid rgba(167,139,250,0.22); border-radius: 100px; font-size: 11px; font-weight: 600; color: #a78bfa; }
body.light-theme .cluster-keywords span { background: rgba(124,58,237,0.07); border-color: rgba(124,58,237,0.18); color: #7c3aed; }
.cluster-links { background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius); overflow: hidden; }
.cluster-links h3 { font-family: 'Bricolage Grotesque', sans-serif; font-size: 14px; font-weight: 700; color: var(--text-dim); text-transform: uppercase; letter-spacing: 0.06em; padding: 14px 20px; border-bottom: 1px solid var(--border); background: var(--bg-3); }
.cluster-link-list { display: flex; flex-direction: column; }
.cluster-link-item { display: flex; align-items: center; gap: 14px; padding: 14px 20px; border-bottom: 1px solid var(--border); transition: background var(--transition); }
.cluster-link-item:last-child { border-bottom: none; }
.cluster-link-item:hover { background: var(--bg-3); }
.cluster-link-icon { flex-shrink: 0; width: 34px; height: 34px; border-radius: 8px; background: rgba(167,139,250,0.10); display: flex; align-items: center; justify-content: center; font-size: 15px; color: #a78bfa; }
body.light-theme .cluster-link-icon { background: rgba(124,58,237,0.07); color: #7c3aed; }
.cluster-link-text { flex: 1; display: flex; flex-direction: column; gap: 2px; }
.cluster-link-text strong { font-size: 14px; font-weight: 600; color: var(--text); }
.cluster-link-text span   { font-size: 12px; color: var(--text-dim); }
.cluster-link-arrow { color: var(--text-dim); font-size: 12px; transition: transform var(--transition), color var(--transition); }
.cluster-link-item:hover .cluster-link-arrow { transform: translateX(3px); color: #a78bfa; }
body.light-theme .cluster-link-item:hover .cluster-link-arrow { color: #7c3aed; }
.cluster-link-all { background: var(--bg-2); }
.cluster-crosslinks { padding-top: 32px; border-top: 1px solid var(--border); }
.cluster-crosslinks h3 { font-family: 'Bricolage Grotesque', sans-serif; font-size: 18px; font-weight: 700; letter-spacing: -0.3px; color: var(--text); margin-bottom: 6px; }
.cluster-crosslinks > p { font-size: 14px; color: var(--text-muted); margin-bottom: 20px; }
.crosslink-grid { display: grid; grid-template-columns: repeat(4, 1fr); gap: 14px; }
.crosslink-card { background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius); padding: 18px 16px; display: flex; flex-direction: column; gap: 8px; transition: border-color var(--transition), transform var(--transition), box-shadow var(--transition); }
.crosslink-card:hover { border-color: #a78bfa; transform: translateY(-3px); box-shadow: var(--shadow); }
body.light-theme .crosslink-card:hover { border-color: #7c3aed; }
.crosslink-card i { font-size: 20px; color: #a78bfa; }
body.light-theme .crosslink-card i { color: #7c3aed; }
.crosslink-card strong { font-family: 'Bricolage Grotesque', sans-serif; font-size: 14px; font-weight: 700; color: var(--text); }
.crosslink-card span { font-size: 12px; line-height: 1.5; color: var(--text-dim); }

/* Ad slot */
.ad-slot { position: relative; z-index: 1; max-width: 1380px; margin: 0 auto; padding: 0 24px 40px; }
.ad-slot > div { background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius); overflow: hidden; }

/* Fade-up */
.fade-up { opacity: 0; transform: translateY(16px); transition: opacity 0.5s ease, transform 0.5s ease; }
.fade-up.visible { opacity: 1; transform: translateY(0); }

/* ============================================
   RESPONSIVE
   ============================================ */

@media (max-width: 1024px) {
  .calc-page { grid-template-columns: 1fr; padding: 32px 20px 60px; gap: 32px; }
  .calc-page-info { position: static; }
  .calc-panel { position: static; order: 2; }
  .calc-page-content { order: 3; }
  .cluster-grid { grid-template-columns: 1fr; }
  .crosslink-grid { grid-template-columns: 1fr 1fr; }
  .prop-app-grid { grid-template-columns: 1fr 1fr; }
}
@media (max-width: 640px) {
  .calc-page { padding: 24px 16px 48px; }
  .crosslink-grid { grid-template-columns: 1fr; }
  .prop-solve-grid { grid-template-columns: 1fr; }
  .prop-app-grid { grid-template-columns: 1fr; }
  .prop-frac-input { font-size: 20px; padding: 10px 8px; }
  .prop-result-answer { font-size: 28px; }
  .topic-cluster-inner { padding: 36px 16px; }
}

@media (min-width: 1025px) {
  .calc-page-info {
    grid-row: 1 / 2;
    grid-column: 1 / 2;
  }
  .calc-page-content {
    grid-row: 2 / 3;
    grid-column: 1 / 2;
  }
  .calc-panel {
    grid-row: 1 / 3;
    grid-column: 2 / 3;
    align-self: start;
    position: sticky;
    top: calc(var(--header-h) + 24px);
  }
}