.lesson31-page{--purple:#7c3aed;--purple-soft:#faf7ff;--ink:#172033;--muted:#475467;--line:#e4e7ec;--green:#147a55;--amber:#9a6700}
.lesson31-content{max-width:900px;margin:0 auto;padding:24px 0 70px;color:var(--ink)}
.lesson31-breadcrumb{display:flex;gap:9px;align-items:center;flex-wrap:wrap;margin:4px 0 22px;color:#667085;font-size:13px}.lesson31-breadcrumb a{color:#6d28d9;text-decoration:none}.lesson31-breadcrumb a:hover{text-decoration:underline}
.lesson31-hero{padding:30px 32px 28px;border:1px solid #e7def6;border-radius:16px;background:linear-gradient(135deg,#fff 0%,#fbf8ff 100%);box-shadow:0 4px 18px rgba(16,24,40,.04)}
.lesson31-label{color:#7c3aed;font-size:12px;font-weight:900;letter-spacing:.08em}.lesson31-hero h1{margin:10px 0 12px;font-size:46px;line-height:1.08;letter-spacing:-.03em}.lesson31-hero p{max-width:780px;margin:0;color:var(--muted);font-size:18px;line-height:1.72}.lesson31-meta{display:flex;gap:10px;align-items:center;flex-wrap:wrap;margin-top:17px;color:#667085;font-size:13px;font-weight:700}
.lesson31-objectives{margin:24px 0;padding:22px 24px;border:1px solid #dcd1f1;border-left:4px solid var(--purple);border-radius:12px;background:#fbf9ff}.lesson31-objectives h2{margin:0 0 12px;font-size:22px}.lesson31-objectives ul{margin:0;padding-left:22px}.lesson31-objectives li{margin:7px 0;color:var(--muted);font-size:15px;line-height:1.6}
.lesson31-section{display:grid;grid-template-columns:36px minmax(0,1fr);gap:15px;margin:42px 0}.lesson31-number{width:36px;height:36px;border-radius:50%;display:grid;place-items:center;background:#efe7ff;color:#6d28d9;font-weight:900;font-size:13px}.lesson31-body{min-width:0}.lesson31-body h2{margin:2px 0 12px;font-size:28px;line-height:1.2;letter-spacing:-.02em}.lesson31-body p{margin:0 0 15px;color:var(--muted);font-size:16px;line-height:1.75}.lesson31-body code,.lesson31-note code{padding:2px 5px;border-radius:5px;background:#f2f4f7;color:#344054;font:600 13px ui-monospace,SFMono-Regular,Menlo,monospace}
.lesson31-definition{display:grid;grid-template-columns:minmax(0,1fr) 210px;border:1px solid #ddd2f0;border-radius:13px;background:#fff;overflow:hidden;margin:20px 0}.lesson31-definition-main{padding:22px;background:#faf8ff}.lesson31-definition-main span,.lesson31-definition-side b{display:block;color:#7c3aed;font-size:11px;font-weight:900;letter-spacing:.07em}.lesson31-definition-main strong{display:block;margin-top:9px;font-size:20px;line-height:1.45}.lesson31-definition-side{padding:18px;border-left:1px solid #e7def6}.lesson31-definition-side b{color:#667085}.lesson31-definition-side span{display:block;margin:4px 0 14px;color:#344054;font-size:14px;font-weight:700}
.lesson31-callout{display:grid;grid-template-columns:max-content minmax(0,1fr);gap:10px;margin:18px 0;padding:15px 17px;border:1px solid #e4e7ec;border-radius:10px;background:#f8fafc;color:var(--muted);font-size:14px;line-height:1.6}.lesson31-callout strong{color:#344054}.lesson31-callout--green{border-color:#cce8dc;background:#f4fbf7}.lesson31-callout--green strong{color:var(--green)}.lesson31-callout--amber{border-color:#ead9ad;background:#fffbef}.lesson31-callout--amber strong{color:var(--amber)}
.lesson31-problem-grid,.lesson31-filter-grid,.lesson31-usecases,.lesson31-operations,.lesson31-checklist,.lesson31-misconceptions,.lesson31-rag-points{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:11px;margin:20px 0}.lesson31-problem-grid>div,.lesson31-filter-grid>div,.lesson31-usecases>div,.lesson31-operations>div,.lesson31-checklist>div,.lesson31-misconceptions>div,.lesson31-rag-points>div{padding:17px;border:1px solid var(--line);border-radius:11px;background:#fff}.lesson31-problem-grid span,.lesson31-usecases span,.lesson31-operations span{display:block;color:#7c3aed;font-size:11px;font-weight:900;letter-spacing:.06em}.lesson31-problem-grid b,.lesson31-usecases b,.lesson31-operations b,.lesson31-checklist b,.lesson31-misconceptions b,.lesson31-rag-points b{display:block;margin:6px 0;font-size:16px}.lesson31-problem-grid p,.lesson31-usecases p,.lesson31-operations p{margin:0;font-size:14px;line-height:1.55}
.lesson31-record{display:grid;grid-template-columns:repeat(4,1fr);gap:9px;margin:20px 0}.lesson31-record-row{padding:15px;border:1px solid var(--line);border-radius:10px;background:#fff}.lesson31-record-row span{display:block;color:#7c3aed;font-size:10px;font-weight:900}.lesson31-record-row strong{display:block;margin:7px 0;font:700 14px ui-monospace,SFMono-Regular,Menlo,monospace;word-break:break-word}.lesson31-record-row small{color:#667085;font-size:12px;line-height:1.45}.lesson31-note{margin:17px 0;padding:13px 15px;border-radius:9px;background:#f8fafc;color:#475467;font-size:14px;line-height:1.6}.lesson31-note strong{color:#344054}
.lesson31-compare{display:grid;grid-template-columns:minmax(0,1fr) auto minmax(0,1fr);gap:10px;align-items:stretch;margin:20px 0}.lesson31-compare-card{padding:20px;border:1px solid var(--line);border-radius:12px;background:#fff}.lesson31-compare-card--purple{border-color:#ddd2f0;background:#fcfaff}.lesson31-compare-card>span{color:#7c3aed;font-size:11px;font-weight:900;letter-spacing:.06em}.lesson31-compare-card h3{margin:7px 0 12px;font-size:20px}.lesson31-compare-card ul{margin:12px 0 0;padding-left:19px;color:var(--muted)}.lesson31-compare-card li{margin:6px 0;font-size:14px;line-height:1.5}.lesson31-vs{align-self:center;color:#98a2b3;font-weight:900}.lesson31-query{padding:12px;border-radius:8px;background:#f8fafc}.lesson31-query b{display:block;color:#667085;font-size:11px;text-transform:uppercase;letter-spacing:.05em}.lesson31-query code{display:block;margin-top:6px;padding:0;background:none;font-size:12px;line-height:1.5}
.lesson31-flow{display:grid;grid-template-columns:1fr auto 1fr auto 1fr auto 1fr;gap:8px;align-items:center;margin:21px 0}.lesson31-flow>div{padding:16px;border:1px solid var(--line);border-radius:10px;background:#fff;text-align:center}.lesson31-flow b,.lesson31-flow span{display:block}.lesson31-flow b{font-size:14px}.lesson31-flow span{margin-top:6px;color:#667085;font-size:12px;line-height:1.45}.lesson31-flow-result{border-color:#ddd2f0!important;background:#faf8ff!important}.lesson31-flow-result b{color:#6d28d9}.lesson31-flow>i{font-style:normal;color:#7c3aed;font-weight:900}
.lesson31-score{display:grid;grid-template-columns:repeat(3,1fr);gap:9px;margin:20px 0}.lesson31-score>div{padding:14px;border:1px solid var(--line);border-radius:10px;background:#fff}.lesson31-score span,.lesson31-score em{display:block;color:#667085;font-size:12px}.lesson31-score strong{display:block;margin:6px 0;font-size:25px;color:#6d28d9}.lesson31-score em{font-style:normal;font-weight:700}
.lesson31-topk{margin:20px 0;padding:18px;border:1px solid var(--line);border-radius:12px;background:#fff}.lesson31-topk-query{padding:14px;border-radius:9px;background:#faf8ff}.lesson31-topk-query span,.lesson31-filter-example span{display:block;color:#7c3aed;font-size:10px;font-weight:900;letter-spacing:.07em}.lesson31-topk-query b{display:block;margin-top:5px;font-size:15px}.lesson31-topk-list{margin-top:10px}.lesson31-topk-list>div{display:grid;grid-template-columns:40px minmax(0,1fr) 60px;gap:10px;align-items:center;padding:10px 5px;border-top:1px solid #edf0f3}.lesson31-topk-list b{color:#7c3aed}.lesson31-topk-list span{font-size:14px;color:#475467}.lesson31-topk-list strong{text-align:right;color:#344054}.lesson31-small-note{font-size:13px!important;color:#667085!important}
.lesson31-filter-example{display:grid;grid-template-columns:minmax(0,1fr) auto minmax(0,1fr) auto minmax(0,1fr);gap:9px;align-items:center;margin:20px 0}.lesson31-filter-example>div{padding:14px;border:1px solid var(--line);border-radius:10px;background:#fff}.lesson31-filter-example strong{display:block;margin-top:5px;font-size:14px}.lesson31-filter-plus,.lesson31-filter-arrow{border:0!important;background:none!important;color:#7c3aed!important;font-weight:900}.lesson31-filter-result{background:#faf8ff!important;border-color:#ddd2f0!important}
.lesson31-index{display:grid;grid-template-columns:1fr auto 1.1fr auto 1fr;gap:8px;align-items:center;margin:20px 0}.lesson31-index>div:not(.lesson31-index-arrow){padding:17px;border:1px solid var(--line);border-radius:10px;background:#fff}.lesson31-index span{display:block;color:#7c3aed;font-size:10px;font-weight:900}.lesson31-index b{display:block;margin:6px 0;font-size:15px}.lesson31-index p{margin:0!important;font-size:13px!important;line-height:1.5!important}.lesson31-index-highlight{border-color:#ddd2f0!important;background:#faf8ff!important}.lesson31-index-arrow{color:#7c3aed;font-weight:900}
.lesson31-rag{display:grid;grid-template-columns:1fr auto 1fr auto 1fr auto 1fr auto 1fr;gap:7px;align-items:center;margin:21px 0}.lesson31-rag>div{min-width:0;padding:15px;border:1px solid var(--line);border-radius:10px;background:#fff;text-align:center}.lesson31-rag b,.lesson31-rag span{display:block}.lesson31-rag b{font-size:14px}.lesson31-rag span{margin-top:5px;color:#667085;font-size:11px;line-height:1.4}.lesson31-rag i{font-style:normal;color:#7c3aed;font-weight:900}.lesson31-rag-highlight{border-color:#ddd2f0!important;background:#faf8ff!important}.lesson31-rag-points{grid-template-columns:repeat(3,1fr)}.lesson31-rag-points span{color:#667085;font-size:13px;line-height:1.5}
.lesson31-layer{display:grid;grid-template-columns:1fr auto 1fr auto 1fr auto 1fr;gap:8px;align-items:center;margin:20px 0}.lesson31-layer>div{padding:15px;border:1px solid var(--line);border-radius:10px;background:#fff;text-align:center}.lesson31-layer span{display:block;color:#7c3aed;font-size:10px;font-weight:900}.lesson31-layer b{display:block;margin-top:6px;font-size:13px}.lesson31-layer i{font-style:normal;color:#7c3aed;font-weight:900}.lesson31-layer-highlight{border-color:#ddd2f0!important;background:#faf8ff!important}
.lesson31-checklist{grid-template-columns:repeat(3,1fr)}.lesson31-checklist span{color:#667085;font-size:13px;line-height:1.45}.lesson31-misconceptions{grid-template-columns:repeat(2,1fr)}.lesson31-misconceptions p{margin:5px 0 0;font-size:14px;line-height:1.55}
.lesson31-practice,.lesson31-quiz{margin:42px 0;padding:25px;border-radius:14px}.lesson31-practice{border:1px solid #ddd2f0;background:#faf8ff}.lesson31-quiz{border:1px solid var(--line);background:#fff}.lesson31-practice-label{color:#7c3aed;font-size:11px;font-weight:900;letter-spacing:.08em}.lesson31-practice h2,.lesson31-quiz h2{margin:7px 0 17px;font-size:28px}.lesson31-practice>p{font-size:16px;color:#475467;line-height:1.7}.lesson31-practice ol{padding-left:22px}.lesson31-practice li{margin:8px 0;color:#475467;font-size:15px;line-height:1.6}.lesson31-practice-box{margin-top:18px;padding:15px;border:1px solid var(--line);border-radius:9px;background:#fff;color:#475467;font-size:14px;line-height:1.6}.lesson31-practice-box strong{color:#6d28d9}.lesson31-question{padding:15px 0;border-top:1px solid #edf0f3}.lesson31-question strong{font-size:15px}.lesson31-question p{margin:6px 0 0;font-size:14px;line-height:1.6}
.lesson31-code{margin:18px 0}.lesson31-code-note{display:grid;grid-template-columns:max-content minmax(0,1fr);gap:10px;margin:13px 0;padding:13px 15px;border-radius:9px;background:#f8fafc;color:#475467;font-size:14px;line-height:1.6}.lesson31-code-note b{color:#344054}.lesson31-recap{margin:42px 0;padding:25px;border-radius:14px;background:#172033;color:#fff}.lesson31-recap h2{margin:6px 0 19px;font-size:28px;color:#fff}.lesson31-recap-flow{display:grid;grid-template-columns:1fr auto 1fr auto 1fr auto 1fr auto 1fr;gap:8px;align-items:center}.lesson31-recap-flow>div{padding:15px;border:1px solid rgba(255,255,255,.15);border-radius:9px;background:rgba(255,255,255,.05)}.lesson31-recap-flow b,.lesson31-recap-flow span{display:block}.lesson31-recap-flow b{font-size:14px}.lesson31-recap-flow span{margin-top:5px;color:#cbd5e1;font-size:12px;line-height:1.4}.lesson31-recap-flow i{font-style:normal;color:#c4b5fd;font-weight:900}.lesson31-takeaways{margin:42px 0;padding:22px;border:1px solid var(--line);border-radius:12px;background:#f8fafc}.lesson31-takeaways h2{margin:0 0 10px;font-size:24px}.lesson31-takeaways ul{margin:0;padding-left:21px}.lesson31-takeaways li{margin:8px 0;color:#475467;font-size:15px;line-height:1.6}.lesson31-bottom-nav{display:flex;justify-content:space-between;gap:12px;margin-top:35px}.lesson31-bottom-nav a{display:block;max-width:48%;padding:13px 15px;border:1px solid var(--line);border-radius:9px;background:#fff;color:#6d28d9;text-decoration:none;font-size:14px;font-weight:700}.lesson31-bottom-nav a:hover{border-color:#d8c7f7;background:#faf8ff}
@media (max-width:1000px){.lesson31-rag,.lesson31-flow,.lesson31-layer,.lesson31-index{grid-template-columns:1fr;gap:8px}.lesson31-rag>i,.lesson31-flow>i,.lesson31-layer>i,.lesson31-index-arrow{display:none}.lesson31-record{grid-template-columns:repeat(2,1fr)}.lesson31-filter-example{grid-template-columns:1fr}.lesson31-filter-plus,.lesson31-filter-arrow{display:none}.lesson31-rag-points{grid-template-columns:1fr}}
@media (max-width:760px){.lesson31-content{padding-top:16px}.lesson31-hero{padding:24px 20px}.lesson31-hero h1{font-size:36px}.lesson31-hero p{font-size:17px}.lesson31-section{grid-template-columns:30px minmax(0,1fr);gap:10px;margin:34px 0}.lesson31-number{width:30px;height:30px;font-size:12px}.lesson31-body h2,.lesson31-practice h2,.lesson31-quiz h2,.lesson31-recap h2{font-size:24px}.lesson31-definition,.lesson31-compare{grid-template-columns:1fr}.lesson31-definition-side{border-left:0;border-top:1px solid #e7def6}.lesson31-vs{justify-self:center}.lesson31-problem-grid,.lesson31-filter-grid,.lesson31-usecases,.lesson31-operations,.lesson31-checklist,.lesson31-misconceptions,.lesson31-rag-points,.lesson31-score{grid-template-columns:1fr}.lesson31-record{grid-template-columns:1fr}.lesson31-code-note{grid-template-columns:1fr}.lesson31-bottom-nav{flex-direction:column}.lesson31-bottom-nav a{max-width:100%}.lesson31-topk-list>div{grid-template-columns:35px minmax(0,1fr) 54px}}
@media (max-width:480px){.lesson31-hero h1{font-size:32px}.lesson31-body p,.lesson31-practice>p{font-size:16px}.lesson31-callout{grid-template-columns:1fr;gap:3px}.lesson31-hero-meta{font-size:12px}.lesson31-topk-list span{font-size:13px}.lesson31-topk-list strong{font-size:13px}}


/* Lesson 31 mobile hardening */
.lesson31-page,
.lesson31-content,
.lesson31-body,
.lesson31-section,
.lesson31-recap,
.lesson31-takeaways,
.lesson31-bottom-nav {
  min-width: 0;
}

.lesson31-body *,
.lesson31-content * {
  max-width: 100%;
  box-sizing: border-box;
}

.lesson31-body p,
.lesson31-body li,
.lesson31-body strong,
.lesson31-body span,
.lesson31-bottom-nav a {
  overflow-wrap: anywhere;
  word-break: normal;
}

@media (max-width: 760px) {
  .lesson31-content {
    width: 100%;
    max-width: 100%;
    overflow-x: hidden;
  }

  .lesson31-hero,
  .lesson31-objectives,
  .lesson31-section,
  .lesson31-practice,
  .lesson31-quiz,
  .lesson31-recap,
  .lesson31-takeaways {
    width: 100%;
  }

  /* Keep the recap readable instead of squeezing five cards into one row. */
  .lesson31-recap-flow {
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 10px;
  }

  .lesson31-recap-flow > div {
    min-width: 0;
    padding: 14px;
  }

  .lesson31-recap-flow i {
    display: none;
  }

  /* Mobile lesson navigation: full-width, readable cards. */
  .lesson31-bottom-nav {
    display: grid;
    grid-template-columns: 1fr;
    gap: 10px;
    width: 100%;
    margin-top: 28px;
  }

  .lesson31-bottom-nav a {
    display: block;
    width: 100%;
    max-width: none;
    min-width: 0;
    padding: 13px 14px;
    line-height: 1.5;
    white-space: normal;
    overflow-wrap: anywhere;
  }
}

@media (max-width: 480px) {
  .lesson31-recap-flow {
    grid-template-columns: 1fr;
  }

  .lesson31-recap-flow > div {
    padding: 13px 14px;
  }

  .lesson31-bottom-nav a {
    font-size: 14px;
  }
}