:root {
  --ink: #1f1f1f;
  --muted: #777777;
  --page: #ffffff;
  --content-width: 1090px;
}

* {
  box-sizing: border-box;
}

html {
  color-scheme: light;
  background: var(--page);
}

body {
  margin: 0;
  color: var(--ink);
  background: var(--page);
  font-family: Arial, Helvetica, sans-serif;
  -webkit-font-smoothing: antialiased;
}

.page-nav {
  position: absolute;
  z-index: 10;
  top: 18px;
  right: max(22px, calc((100% - var(--content-width)) / 2));
  display: flex;
  gap: 4px;
  padding: 5px;
  border: 1px solid rgba(0, 0, 0, 0.12);
  border-radius: 999px;
  background: rgba(255, 255, 255, 0.88);
  box-shadow: 0 6px 22px rgba(0, 0, 0, 0.08);
  backdrop-filter: blur(8px);
}

.page-nav a {
  padding: 8px 13px;
  border-radius: 999px;
  color: #333;
  font-size: 0.8rem;
  font-weight: 700;
  text-decoration: none;
}

.page-nav a:hover,
.page-nav a:focus-visible,
.page-nav a.active {
  color: #fff;
  background: #164f80;
}

img {
  display: block;
  max-width: 100%;
}

.container {
  width: min(var(--content-width), calc(100% - 72px));
  margin-inline: auto;
}

.hero {
  position: relative;
  display: grid;
  min-height: 344px;
  overflow: hidden;
  place-items: center;
  isolation: isolate;
}

.hero__image,
.hero__wash {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
}

.hero__image {
  z-index: -2;
  object-fit: cover;
  object-position: center 48%;
  transform: scale(1.015);
}

.hero__wash {
  z-index: -1;
  background: rgba(255, 255, 255, 0.72);
}

.hero h1 {
  max-width: 800px;
  margin: 4px 24px 0;
  color: #080808;
  font-size: clamp(1.75rem, 2.45vw, 2.2rem);
  font-weight: 700;
  line-height: 1.15;
  text-align: center;
}

.chemicals {
  padding: 62px 0 58px;
}

.chemicals h2 {
  margin: 0 0 46px;
  font-size: clamp(1.6rem, 2.2vw, 2rem);
  line-height: 1.15;
}

.chemical-grid {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  column-gap: 72px;
  row-gap: 72px;
}

.chemical-card {
  display: grid;
  grid-template-columns: 40px 1fr;
  align-items: start;
  gap: 16px;
}

.info-icon {
  display: grid;
  width: 30px;
  height: 30px;
  margin-top: 2px;
  border: 3px solid currentColor;
  border-radius: 50%;
  font-family: Georgia, serif;
  font-size: 1rem;
  font-weight: 700;
  line-height: 1;
  place-items: center;
}

.chemical-card h3 {
  margin: 0 0 12px;
  font-size: 1.35rem;
  line-height: 1.1;
}

.chemical-card h3 span {
  margin-right: 7px;
}

.chemical-card p {
  margin: 0;
  color: var(--muted);
  font-size: 1rem;
  line-height: 1.38;
}

.membranes {
  padding: 72px 0 92px;
}

.membrane-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 54px;
  align-items: center;
}

.membrane-grid figure {
  margin: 0;
}

.membrane-grid img {
  width: 100%;
  aspect-ratio: 1.45 / 1;
  object-fit: contain;
}

.hero--about {
  min-height: 345px;
}

.hero--about .hero__image {
  object-position: center 48%;
  transform: none;
}

.hero--about .hero__wash {
  background: rgba(255, 255, 255, 0.1);
}

.about-chemicals {
  padding: 64px 0 100px;
}

.about-intro {
  max-width: 1020px;
  margin: 0 0 68px;
  font-size: clamp(1.2rem, 1.7vw, 1.45rem);
  line-height: 1.35;
}

.purpose-grid {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 92px 50px;
}

.purpose-card {
  display: flex;
  min-height: 285px;
  overflow: hidden;
  flex-direction: column;
  padding: 20px 20px 24px;
  border: 1px solid #d9d9d9;
  border-radius: 8px;
  background: #fff;
}

.purpose-card img {
  width: 100%;
  height: 180px;
  margin-bottom: 18px;
  object-fit: contain;
}

.purpose-card h2 {
  margin: auto 0 0;
  font-size: 1.35rem;
  line-height: 1.12;
}

.guide-page {
  background: #f7f9fb;
}

.guide-hero {
  padding: 128px 0 72px;
  color: #fff;
  background: linear-gradient(120deg, #063b60, #0878a7);
}

.eyebrow {
  margin: 0 0 12px;
  color: #9cdef3;
  font-size: 0.82rem;
  font-weight: 800;
  letter-spacing: 0.14em;
  text-transform: uppercase;
}

.guide-hero h1 {
  max-width: 850px;
  margin: 0;
  font-size: clamp(2.25rem, 5vw, 4.25rem);
  line-height: 1.02;
}

.guide-hero p:last-child {
  max-width: 760px;
  margin: 24px 0 0;
  color: #d9f0f7;
  font-size: 1.12rem;
  line-height: 1.55;
}

.guide-layout {
  display: grid;
  grid-template-columns: 220px minmax(0, 1fr);
  gap: 54px;
  padding-block: 72px 110px;
}

.guide-toc {
  position: sticky;
  top: 28px;
  align-self: start;
  display: grid;
  gap: 7px;
  padding: 22px;
  border: 1px solid #dfe6ea;
  border-radius: 14px;
  background: #fff;
}

.guide-toc strong {
  margin-bottom: 7px;
}

.guide-toc a {
  color: #54636d;
  font-size: 0.83rem;
  line-height: 1.3;
  text-decoration: none;
}

.guide-toc a:hover,
.guide-toc a:focus-visible {
  color: #0878a7;
}

.guide-content {
  min-width: 0;
}

.guide-section {
  display: grid;
  grid-template-columns: minmax(0, 1.25fr) minmax(240px, 0.75fr);
  gap: 42px;
  align-items: center;
  margin-bottom: 36px;
  padding: 48px;
  border: 1px solid #e1e7ea;
  border-radius: 18px;
  background: #fff;
  box-shadow: 0 10px 34px rgba(23, 53, 70, 0.06);
  scroll-margin-top: 24px;
}

.guide-section--reverse .section-copy {
  order: 2;
}

.guide-section--reverse .section-image {
  order: 1;
}

.guide-section--full {
  display: block;
}

.section-number {
  margin: 0 0 8px;
  color: #0878a7;
  font-size: 0.8rem;
  font-weight: 900;
  letter-spacing: 0.14em;
}

.guide-section h2 {
  margin: 0 0 20px;
  font-size: clamp(1.8rem, 3vw, 2.45rem);
  line-height: 1.08;
}

.guide-section h3 {
  margin: 34px 0 16px;
  font-size: 1.35rem;
}

.guide-section p {
  color: #53616a;
  line-height: 1.65;
}

.section-image {
  width: 100%;
  max-height: 360px;
  object-fit: contain;
}

.check-list {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 9px 20px;
  margin: 24px 0 0;
  padding: 0;
  list-style: none;
}

.check-list li {
  position: relative;
  padding-left: 20px;
  color: #33434c;
  font-size: 0.9rem;
  line-height: 1.35;
}

.check-list li::before {
  position: absolute;
  left: 0;
  color: #1290bd;
  content: "✓";
  font-weight: 900;
}

.safety-note,
.guide-conclusion {
  margin-top: 24px;
  padding: 18px 20px;
  border-left: 4px solid #e0a625;
  border-radius: 6px;
  color: #5f4a1e;
  background: #fff8e6;
  line-height: 1.55;
}

.brand-grid,
.metric-grid,
.selection-grid {
  display: grid;
  gap: 18px;
  margin-top: 30px;
}

.brand-grid {
  grid-template-columns: repeat(2, minmax(0, 1fr));
}

.brand-grid article,
.metric-grid article,
.selection-grid li {
  padding: 24px;
  border: 1px solid #dfe6ea;
  border-radius: 12px;
  background: #fbfcfd;
}

.brand-grid h3 {
  margin: 0 0 8px;
}

.brand-grid p {
  margin: 0;
}

.metric-grid {
  grid-template-columns: repeat(3, minmax(0, 1fr));
}

.metric-grid strong {
  display: block;
  margin-bottom: 8px;
  color: #0878a7;
  font-size: 2rem;
}

.metric-grid span {
  color: #53616a;
  font-size: 0.9rem;
  line-height: 1.4;
}

.steps-list {
  display: grid;
  gap: 13px;
  padding-left: 24px;
  color: #53616a;
  line-height: 1.55;
}

.selection-grid {
  grid-template-columns: repeat(2, minmax(0, 1fr));
  padding: 0;
  list-style: none;
  counter-reset: selection;
}

.selection-grid li {
  counter-increment: selection;
}

.selection-grid strong,
.selection-grid span {
  display: block;
}

.selection-grid strong::before {
  margin-right: 8px;
  color: #0878a7;
  content: counter(selection, decimal-leading-zero);
}

.selection-grid span {
  margin-top: 10px;
  color: #65737b;
  font-size: 0.9rem;
  line-height: 1.5;
}

.faq-list {
  display: grid;
  gap: 10px;
  margin-top: 28px;
}

.faq-list details {
  padding: 17px 20px;
  border: 1px solid #dfe6ea;
  border-radius: 10px;
  background: #fff;
}

.faq-list summary {
  cursor: pointer;
  font-weight: 750;
}

.faq-list p {
  margin-bottom: 0;
}

.guide-conclusion {
  border-left-color: #0878a7;
  color: #173f51;
  background: #eaf7fb;
}

.guide-conclusion h3 {
  margin-top: 0;
}

@media (max-width: 900px) {
  .hero {
    min-height: 285px;
  }

  .chemical-grid {
    grid-template-columns: repeat(2, minmax(0, 1fr));
    column-gap: 48px;
  }

  .purpose-grid {
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 44px;
  }

  .guide-layout {
    grid-template-columns: 1fr;
  }

  .guide-toc {
    position: static;
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }

  .guide-toc strong {
    grid-column: 1 / -1;
  }
}

@media (max-width: 620px) {
  .container {
    width: min(100% - 36px, var(--content-width));
  }

  .hero {
    min-height: 235px;
  }

  .page-nav {
    position: relative;
    top: auto;
    right: auto;
    justify-content: center;
    padding: 7px;
    border: 0;
    border-radius: 0;
    box-shadow: none;
  }

  .page-nav a {
    padding: 8px 10px;
    font-size: 0.72rem;
  }

  .hero h1 {
    font-size: 1.65rem;
  }

  .chemicals {
    padding: 46px 0 34px;
  }

  .chemicals h2 {
    margin-bottom: 36px;
  }
 
  .chemical-grid,
  .membrane-grid {
    grid-template-columns: 1fr;
  }

  .chemical-grid {
    row-gap: 38px;
  }

  .chemical-card {
    grid-template-columns: 34px 1fr;
    gap: 12px;
  }

  .chemical-card h3 {
    font-size: 1.22rem;
  }

  .membranes {
    padding: 42px 0 60px;
  }

  .membrane-grid {
    gap: 20px;
  }

  .hero--about {
    min-height: 240px;
  }

  .about-chemicals {
    padding: 44px 0 64px;
  }

  .about-intro {
    margin-bottom: 42px;
  }

  .purpose-grid {
    grid-template-columns: 1fr;
    gap: 26px;
  }

  .purpose-card {
    min-height: 270px;
  }

  .guide-hero {
    padding: 70px 0 52px;
  }

  .guide-layout {
    gap: 30px;
    padding-block: 36px 64px;
  }

  .guide-toc {
    grid-template-columns: 1fr;
  }

  .guide-section,
  .guide-section--reverse {
    grid-template-columns: 1fr;
    gap: 24px;
    padding: 28px 22px;
  }

  .guide-section--reverse .section-copy,
  .guide-section--reverse .section-image {
    order: initial;
  }

  .section-image {
    max-height: 260px;
  }

  .check-list,
  .brand-grid,
  .metric-grid,
  .selection-grid {
    grid-template-columns: 1fr;
  }
  }
  .shop-link {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  margin-top: 20px;
  padding: 12px 22px;
  border-radius: 999px;
  color: #fff;
  font-size: 0.9rem;
  font-weight: 700;
  text-decoration: none;
  background: #0878a7;
  transition: background 0.15s ease;
}

.shop-link:hover,
.shop-link:focus-visible {
  background: #063b60;
}
.site-footer {
  margin-top: 40px;
  padding: 16px 0;
  background: #2597e3;
}
.site-footer .container {
  display: flex;
  flex-direction: column;
  align-items: flex-start;
  text-align: left;
  justify-content: space-between;
  gap: 14px;
}

.footer-brand {
  color: #fff;
  font-size: 0.9rem;
  font-weight: 700;
  text-align: left;
}

.footer-contact {
  color: #b7cbd8;
  font-size: 0.85rem;
  text-align: left;
}


.footer-bottom {
  width: min(var(--content-width), calc(100% - 72px));
  margin: 16px auto 0;
  padding-top: 14px;
  border-top: 1px solid rgba(255, 255, 255, 0.2);
  color: #b7cbd8;
  font-size: 0.8rem;
  text-align: left;
}

@media (max-width: 620px) {
  .footer-bottom {
    width: min(100% - 36px, var(--content-width));
  }
}