:root {
  --ink: #365a78;
  --ink-soft: #5a7b95;
  --teal: #148e9c;
  --teal-light: #d0f0f0;
  --blue: #dfedf7;
  --sky: #f1f9fe;
  --paper: #ffffff;
  --line: #c5dfe9;
  --orange: #ee8c6e;
  --orange-light: #fff1eb;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body { margin: 0; background: var(--sky); color: var(--ink); font-family: system-ui, -apple-system, "Segoe UI", sans-serif; line-height: 1.62; }
a { color: #167f99; text-decoration: underline; text-underline-offset: 3px; }
a:hover { color: #cb6f58; }
a:focus-visible, summary:focus-visible { outline: 3px solid var(--orange); outline-offset: 4px; border-radius: 3px; }
h1, h2, h3, p { margin-top: 0; }
h1 { font-size: 40px; line-height: 1.15; letter-spacing: -.038em; font-weight: 760; }
h2 { font-size: 28px; line-height: 1.22; letter-spacing: -.026em; font-weight: 730; }
h3 { font-size: 20px; line-height: 1.3; letter-spacing: -.014em; }
p { font-size: 16px; line-height: 1.7; }
ul { padding-left: 22px; }
.shell { width: min(1230px, calc(100% - 64px)); margin-inline: auto; }
.eyebrow { display: inline-block; color: var(--teal); font-size: 12px; font-weight: 760; letter-spacing: .14em; text-transform: uppercase; margin-bottom: 14px; }

.site-header { background: rgba(243,250,254,.98); border-bottom: 1px solid var(--line); }
.header-line { min-height: 76px; display: flex; align-items: center; justify-content: space-between; gap: 23px; }
.mark { display: flex; align-items: center; gap: 12px; color: var(--ink); text-decoration: none; font-size: 19px; line-height: 1; font-weight: 800; letter-spacing: .055em; white-space: nowrap; }
.mark small { display: block; margin-top: 7px; font-size: 10px; letter-spacing: .13em; font-weight: 740; color: var(--teal); }
.mark-symbol { position: relative; width: 40px; height: 43px; flex: none; border: 2px solid #72b6c9; border-radius: 8px; background: white; box-shadow: inset 0 0 0 5px #e4f3f9; }
.mark-symbol::before { content: ""; position: absolute; left: 5px; right: 5px; top: 17px; border-top: 2px solid #72b6c9; }
.mark-symbol::after { content: ""; position: absolute; top: 5px; right: 6px; width: 5px; height: 5px; background: var(--orange); border-radius: 50%; }
.desktop-navigation { display: flex; align-items: center; gap: 21px; flex-wrap: wrap; }
.desktop-navigation a { text-decoration: none; font-size: 14px; font-weight: 660; color: var(--ink-soft); }
.desktop-navigation a:hover, .desktop-navigation a[aria-current] { color: var(--teal); }
.mobile-navigation { display: none; }

.hero { display: grid; grid-template-columns: 1.08fr .92fr; gap: 36px; align-items: center; padding-top: 55px; padding-bottom: 47px; }
.hero-copy { max-width: 640px; }
.hero-copy h1 { margin-bottom: 22px; max-width: 620px; }
.hero-copy p { margin-bottom: 17px; }
.hero-actions { display: flex; flex-wrap: wrap; gap: 12px; margin-top: 25px; }
.primary-action, .secondary-action { display: inline-block; text-decoration: none; border-radius: 8px; padding: 11px 18px; font-size: 14px; font-weight: 670; }
.primary-action { background: var(--teal); color: white; }
.primary-action:hover { background: #167d8a; color: white; }
.secondary-action { color: var(--ink); border: 1px solid #9ac2d2; background: white; }
.secondary-action:hover { color: var(--teal); background: var(--teal-light); }
.hero-media { display: grid; grid-template-columns: .84fr 1.16fr; gap: 18px; align-items: center; padding: 25px 23px; border: 1px solid #add5e3; border-radius: 22px; background: linear-gradient(150deg,#d9edf6,#e6f6f8); }
.fridge-illustration { display: flex; justify-content: center; align-items: center; min-width: 0; }
.fridge-body { position: relative; height: 315px; width: min(176px,100%); border: 3px solid #94c7d7; background: white; border-radius: 14px 14px 10px 10px; box-shadow: 0 12px 0 #a3cbd9, 0 21px 20px rgba(85,141,167,.14); padding: 7px; display: grid; grid-template-rows: 1.1fr .9fr; gap: 8px; }
.fridge-top-door { position: relative; background: linear-gradient(160deg,#f9fdff,#eaf5fa); border: 1px solid #b4d7e3; border-radius: 7px; }
.fridge-bottom-door { position: relative; background: linear-gradient(160deg,#f3fbfe,#e6f4f9); border: 1px solid #b4d7e3; border-radius: 7px; }
.top-handle, .bottom-handle { position: absolute; right: 12px; background: #92c6d8; width: 7px; height: 41px; border-radius: 4px; box-shadow: inset 2px 0 #c4e2ec; }
.top-handle { bottom: 14px; }
.bottom-handle { top: 15px; }
.temp-dot { position: absolute; top: 15px; right: 16px; height: 7px; width: 7px; border-radius: 50%; background: var(--orange); }
.cold-glyph { display: block; position: absolute; top: 35px; left: 28px; width: 47px; height: 47px; border: 3px solid #a7dbe1; border-radius: 50%; }
.cold-glyph::before { content: ""; position: absolute; width: 3px; height: 31px; top: 5px; left: 19px; background: #43b6c4; transform: rotate(45deg); border-radius: 4px; }
.cold-glyph::after { content: ""; position: absolute; width: 31px; height: 3px; top: 19px; left: 5px; background: #43b6c4; transform: rotate(45deg); border-radius: 4px; }
.fridge-drawer { position: absolute; top: 54px; left: 22px; right: 37px; height: 48px; background: #daf1f6; border: 2px solid #acd6e2; border-radius: 4px; display: flex; justify-content: space-around; align-items: end; padding: 7px; }
.fridge-drawer span { width: 17px; height: 20px; border-radius: 8px 8px 5px 5px; background: #77c6d0; transform: rotate(-5deg); }
.fridge-drawer span:nth-child(2) { height: 27px; background: #9edbdd; transform: rotate(6deg); }
.fridge-drawer span:nth-child(3) { height: 17px; background: #f1a488; transform: rotate(8deg); }
.fridge-body .foot { position: absolute; bottom: -15px; width: 18px; height: 7px; background: #91b4c4; border-radius: 1px 1px 4px 4px; }
.fridge-body .left { left: 14px; }
.fridge-body .right { right: 14px; }
.media-facts { min-width: 0; }
.fact-small { display: block; color: var(--teal); font-size: 11px; font-weight: 790; letter-spacing: .12em; margin-bottom: 5px; }
.media-facts strong { display: block; font-size: clamp(28px,3vw,39px); line-height: 1.17; color: var(--ink); letter-spacing: -.04em; }
.media-facts strong small { font-size: 13px; letter-spacing: 0; font-weight: 650; }
.media-facts p { margin: 9px 0 19px; line-height: 1.5; }

.feature-ledger { background: white; border: 1px solid var(--line); border-radius: 14px; overflow: hidden; margin-bottom: 64px; }
.ledger-head { display: flex; align-items: center; gap: 24px; background: var(--ink); color: white; padding: 16px 25px; }
.ledger-head span { color: #b7e9ef; font-size: 12px; font-weight: 770; letter-spacing: .12em; white-space: nowrap; }
.ledger-head h2 { margin: 0; color: white; }
.ledger-items { display: grid; grid-template-columns: repeat(3,minmax(0,1fr)); }
.ledger-items article { padding: 20px 25px; border-right: 1px solid var(--line); }
.ledger-items article:last-child { border-right: 0; }
.ledger-items strong { display: block; color: var(--teal); font-size: 27px; line-height: 1.25; letter-spacing: -.025em; }
.ledger-items span { display: block; font-size: 14px; line-height: 1.5; margin-top: 9px; }
.ledger-note { padding: 18px 25px 21px; margin: 0; background: #e9f7fa; border-top: 1px solid var(--line); }

.topic-section { margin-bottom: 64px; }
.section-title { margin-bottom: 23px; }
.section-title h2 { margin: 0; }
.section-title-split { display: grid; grid-template-columns: 1fr 1fr; align-items: end; gap: 32px; }
.section-title-split p { margin: 0; }
.topic-grid { display: grid; grid-template-columns: repeat(3,minmax(0,1fr)); gap: 15px; }
.topic-card { background: white; border: 1px solid var(--line); border-radius: 12px; border-top: 3px solid #87cbd1; padding: 21px 23px 17px; display: flex; flex-direction: column; }
.topic-card:nth-child(3n+2) { background: #eaf6fa; }
.card-index { font-size: 11px; font-weight: 760; letter-spacing: .1em; color: var(--teal); text-transform: uppercase; }
.topic-card h3 { margin: 13px 0 11px; }
.topic-card h3 a { color: #167f99; text-decoration: underline; }
.topic-card h3 a:hover { color: #cb6f58; }
.topic-card p { margin: 0; line-height: 1.55; }

.observations { margin-bottom: 55px; padding: 31px 34px; border-radius: 14px; background: #ddf1f3; }
.observation-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 35px; }
.observation-grid p { margin-bottom: 0; }
.sources { margin-top: 55px; margin-bottom: 67px; padding-top: 23px; border-top: 1px solid var(--line); }
.sources h2 { margin-bottom: 16px; }
.sources ol { margin: 0; padding-left: 23px; }
.sources li { font-size: 14px; line-height: 1.6; margin-bottom: 10px; padding-left: 5px; }

.article-intro { display: grid; grid-template-columns: minmax(0,1.22fr) minmax(310px,.78fr); align-items: stretch; gap: 39px; margin-top: 49px; margin-bottom: 60px; }
.breadcrumbs { display: flex; align-items: center; gap: 11px; font-size: 13px; margin-bottom: 21px; color: var(--ink-soft); }
.article-heading h1 { margin-bottom: 21px; }
.article-heading p { margin-bottom: 15px; }
.article-facts { background: linear-gradient(160deg,#def2f7,#d3ecee); border: 1px solid #a8d4df; border-radius: 14px; padding: 23px 25px; display: flex; flex-direction: column; }
.fact-top { display: flex; justify-content: space-between; color: var(--teal); font-size: 12px; font-weight: 760; letter-spacing: .1em; }
.pulse { height: 14px; width: 14px; border: 3px solid var(--orange); border-radius: 50%; }
.article-facts h2 { margin: 19px 0 15px; }
.article-facts p { margin-bottom: 17px; }
.article-facts ul { margin: auto 0 0; background: white; border: 1px solid var(--line); border-radius: 9px; padding: 14px 16px 14px 36px; }
.article-facts li { margin-bottom: 7px; }
.article-facts li:last-child { margin-bottom: 0; }

.chapter { margin-bottom: 61px; }
.chapter-pair { display: grid; grid-template-columns: 1fr 1fr; gap: 17px; }
.prose-block { padding: 27px 29px 15px; background: white; border: 1px solid var(--line); border-radius: 12px; }
.prose-block.lighter { background: #e7f4f9; }
.prose-block p { margin-bottom: 14px; }
.exam-band { margin-bottom: 61px; padding: 39px 0 35px; background: #e0f0f6; border-block: 1px solid #c5dfe8; }
.steps { display: grid; grid-template-columns: repeat(3,minmax(0,1fr)); gap: 14px; }
.step { padding: 22px 24px 18px; border-radius: 11px; border: 1px solid var(--line); background: white; }
.step-number { display: inline-grid; place-items: center; height: 35px; width: 39px; background: #c9eef0; color: var(--teal); border-radius: 7px; font-weight: 780; }
.step h3 { margin: 15px 0 10px; }
.step p { margin: 0; }
.exam-note { margin: 19px 0 0; padding-left: 18px; border-left: 3px solid var(--teal); }
.compare-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 17px; }
.compare-item { padding: 24px 27px 20px; border: 1px solid var(--line); border-radius: 12px; background: #ecf8fb; }
.compare-item.second { background: var(--orange-light); border-color: #eac8bd; }
.compare-letter { display: inline-block; margin-bottom: 9px; color: var(--teal); font-size: 13px; font-weight: 800; }
.second .compare-letter { color: #c87056; }
.compare-item h3 { margin-bottom: 11px; }
.compare-item p { margin: 0; }
.post-compare { margin: 19px 0 0; }
.post-compare+.post-compare { margin-top: 12px; }
.analysis-section { display: grid; grid-template-columns: 1.14fr .86fr; align-items: stretch; gap: 23px; margin-bottom: 60px; }
.analysis-note { padding: 26px 29px; background: white; border: 1px solid var(--line); border-radius: 13px; }
.analysis-note h2 { margin-bottom: 12px; }
.analysis-note p { margin: 0; }
.formula-box { padding: 26px 29px; border-radius: 13px; background: #d3eff0; border: 1px solid #a5d6da; }
.formula-box span { display: block; color: var(--teal); font-size: 13px; font-weight: 740; letter-spacing: .08em; text-transform: uppercase; }
.formula-box strong { display: block; font-size: clamp(27px,3vw,38px); line-height: 1.25; letter-spacing: -.04em; margin: 11px 0; }
.formula-box p { margin: 0; }
.related { margin-top: 37px; margin-bottom: 73px; }
.related-grid { display: grid; grid-template-columns: repeat(3,minmax(0,1fr)); gap: 13px; }
.related-grid a { padding: 18px 19px; border: 1px solid var(--line); border-radius: 9px; background: white; color: #167f99; text-decoration: underline; font-size: 17px; font-weight: 660; }
.related-grid a:hover { color: var(--teal); background: var(--teal-light); }
.related-grid span { display: block; margin-bottom: 7px; font-size: 11px; font-weight: 740; letter-spacing: .11em; text-transform: uppercase; color: var(--teal); }
.context-link { color: inherit; text-decoration: none; font-weight: inherit; }
.context-link:hover { color: var(--teal); background: #dcf4f2; }

.home-hero { display: grid; grid-template-columns: 1.15fr .85fr; align-items: center; gap: 45px; padding-top: 57px; margin-bottom: 60px; }
.home-hero h1 { max-width: 650px; }
.home-indicator { padding: 22px 27px 29px; border: 1px solid #aad7e0; border-radius: 18px; background: #d7eff3; text-align: center; }
.home-indicator>span { color: var(--teal); font-size: 12px; font-weight: 770; letter-spacing: .15em; }
.home-indicator strong { display: block; font-size: 20px; margin: 10px 0; }
.home-indicator p { margin: 0; }
.radial { display: grid; place-items: center; width: 166px; height: 166px; margin: 20px auto; border: 21px solid #9bdae0; border-top-color: var(--teal); border-right-color: var(--orange); border-radius: 50%; background: white; }
.radial b { color: var(--teal); font-size: 40px; }
.home-phases { margin-bottom: 63px; }
.phase-grid { display: grid; grid-template-columns: repeat(3,minmax(0,1fr)); gap: 17px; }
.phase-grid article { display: flex; flex-direction: column; padding: 24px 25px; background: white; border: 1px solid var(--line); border-radius: 12px; }
.phase-grid span { font-size: 12px; letter-spacing: .1em; font-weight: 770; color: var(--teal); }
.phase-grid h3 { margin: 15px 0 10px; }
.phase-grid p { margin-bottom: 14px; }
.phase-grid a { margin-top: auto; font-size: 14px; }

.site-footer { padding: 31px 0; border-top: 1px solid var(--line); background: #dceef5; }
.footer-grid { display: flex; align-items: center; justify-content: space-between; gap: 35px; }
.footer-name { font-size: 17px; font-weight: 800; }
.footer-grid p { margin: 6px 0 0; }
.footer-grid nav { display: flex; flex-wrap: wrap; align-items: center; gap: 18px; }
.footer-grid nav a { font-size: 14px; }

@media (max-width: 1120px) {
  .shell { width: min(100% - 40px, 1230px); }
  .header-line { gap: 12px; }
  .desktop-navigation { gap: 12px; }
  .desktop-navigation a { font-size: 13px; }
  .hero { gap: 21px; }
  .hero-media { grid-template-columns: 1fr; gap: 18px; }
  .fridge-body { width: 144px; height: 245px; }
  .fridge-drawer { top: 38px; left: 16px; right: 30px; height: 41px; }
  .fridge-drawer span { width: 13px; height: 16px; }
  .fridge-drawer span:nth-child(2) { height: 23px; }
  .fridge-drawer span:nth-child(3) { height: 16px; }
  .cold-glyph { top: 25px; left: 16px; }
  .article-intro { grid-template-columns: 1.12fr .88fr; gap: 25px; }
}

@media (max-width: 810px) {
  .desktop-navigation { display: none; }
  .mobile-navigation { display: block; position: relative; }
  .mobile-navigation summary { cursor: pointer; padding: 9px 14px; background: white; border: 1px solid #8cbbc8; border-radius: 8px; font-weight: 680; }
  .mobile-navigation nav { display: grid; position: absolute; right: 0; top: calc(100% + 8px); z-index: 5; width: min(260px, calc(100vw - 40px)); background: white; padding: 10px; border: 1px solid var(--line); border-radius: 11px; box-shadow: 0 12px 18px #a5cbd876; }
  .mobile-navigation nav a { padding: 8px 10px; }
  .hero, .article-intro, .home-hero { grid-template-columns: 1fr; }
  .hero { padding-top: 35px; }
  .hero-media { grid-template-columns: .8fr 1.2fr; }
  .fridge-body { height: 275px; width: 159px; }
  .fridge-drawer { top: 49px; }
  .article-intro { margin-top: 35px; margin-bottom: 45px; }
  .article-facts ul { margin-top: 10px; }
  .section-title-split { grid-template-columns: 1fr; gap: 8px; }
  .topic-grid { grid-template-columns: repeat(2,minmax(0,1fr)); }
  .footer-grid { flex-direction: column; align-items: flex-start; }
}

@media (max-width: 620px) {
  .shell { width: calc(100% - 30px); }
  h1 { font-size: 40px; overflow-wrap: anywhere; }
  h2 { font-size: 28px; overflow-wrap: anywhere; }
  p { font-size: 16px; }
  .mark { font-size: 17px; }
  .hero, .home-hero { padding-top: 29px; }
  .hero-media { grid-template-columns: 1fr; padding: 23px; }
  .media-facts p:last-child { margin-bottom: 0; }
  .feature-ledger { margin-bottom: 43px; }
  .ledger-head { flex-direction: column; align-items: flex-start; gap: 6px; padding: 17px; }
  .ledger-items { grid-template-columns: 1fr; }
  .ledger-items article { border-right: 0; border-bottom: 1px solid var(--line); padding: 15px 19px; }
  .ledger-note { padding: 17px 19px; }
  .topic-grid, .steps, .compare-grid, .chapter-pair, .phase-grid, .related-grid, .observation-grid, .analysis-section { grid-template-columns: 1fr; }
  .topic-section, .chapter, .exam-band, .home-phases { margin-bottom: 42px; }
  .observations { padding: 22px; margin-bottom: 35px; }
  .article-facts { padding: 20px; }
  .prose-block { padding: 21px; }
  .exam-band { padding: 28px 0; }
  .compare-item, .analysis-note, .formula-box { padding: 21px; }
  .sources { margin: 35px auto 47px; }
  .related { margin-bottom: 47px; }
  .site-footer { padding: 26px 0; }
}