:root {
  --paper: #f3f0e8;
  --white: #fffdf8;
  --ink: #17211c;
  --muted: #626b65;
  --sage: #82a38d;
  --sage-dark: #315b45;
  --acid: #d9eb57;
  --rust: #a8543e;
  --line: rgba(23,33,28,.17);
  --edge: clamp(1.25rem,4.5vw,5.5rem);
  --page: min(82rem,calc(100vw - var(--edge) - var(--edge)));
}

body { overflow-x: hidden; color: var(--ink); background: var(--paper); }
.site-header { color: var(--ink); border-bottom: 1px solid var(--line); background: rgba(255,253,248,.94); backdrop-filter: blur(14px); }
.site-header::before { display: none; }
.site-header.scrolled { background: rgba(255,253,248,.96); }
.problem-footer { color: var(--ink); border-top: 1px solid var(--line); background: var(--white); }
.footer-links { display: grid; grid-template-columns: repeat(3,max-content); gap: 2rem; justify-content: end; }
.footer-links a { font-size: .72rem; text-decoration: none; }
.sr-only { position: absolute; width: 1px; height: 1px; padding: 0; overflow: hidden; clip: rect(0,0,0,0); white-space: nowrap; border: 0; }

/* 问题目录：先看图片，再进入单独答案页 */
.problem-index { padding: clamp(9rem,13vw,12rem) var(--edge) clamp(5rem,8vw,8rem); }
.problem-index__hero { display: grid; grid-template-columns: minmax(0,1.18fr) minmax(18rem,.82fr); gap: clamp(2rem,7vw,8rem); align-items: end; width: var(--page); margin: 0 auto clamp(3.5rem,6vw,6rem); }
.problem-index__hero > p { grid-column: 1 / -1; margin: 0; color: var(--sage-dark); font: 700 .67rem/1.5 Arial,sans-serif; letter-spacing: .2em; }
.problem-index__hero h1 { margin: 0; font: 400 clamp(3.4rem,6.5vw,6.8rem)/.98 STSong,"Noto Serif SC",serif; letter-spacing: -.065em; }
.problem-index__hero > div { display: grid; gap: .8rem; padding: 1.4rem 0 .25rem; border-top: 1px solid var(--ink); }
.problem-index__hero strong { font: 400 clamp(1.15rem,1.8vw,1.7rem)/1.45 STSong,"Noto Serif SC",serif; }
.problem-index__hero span { max-width: 31rem; color: var(--muted); font-size: .82rem; line-height: 1.9; }

.problem-directory { display: grid; grid-template-columns: repeat(2,minmax(0,1fr)); width: var(--page); margin: 0 auto; border-top: 1px solid var(--line); border-left: 1px solid var(--line); }
.problem-entry { display: grid; grid-template-columns: minmax(0,1.14fr) minmax(14rem,.86fr); min-height: 25rem; color: var(--ink); border-right: 1px solid var(--line); border-bottom: 1px solid var(--line); background: var(--white); text-decoration: none; }
.problem-entry figure { position: relative; min-width: 0; min-height: 22rem; margin: 0; overflow: hidden; background: #d8d5ce; }
.problem-entry figure::after { position: absolute; inset: 0; background: linear-gradient(180deg,transparent 65%,rgba(12,19,15,.42)); content: ""; pointer-events: none; }
.problem-entry figure img { width: 100%; height: 100%; object-fit: cover; transition: transform .7s cubic-bezier(.22,1,.36,1); }
.problem-entry figcaption { position: absolute; z-index: 1; right: 1rem; bottom: .9rem; color: white; font-size: .57rem; letter-spacing: .12em; }
.problem-entry > div { display: flex; flex-direction: column; min-width: 0; padding: clamp(1.5rem,2.5vw,2.5rem); }
.problem-entry > div > span { color: var(--rust); font: 700 .57rem/1.5 Arial,sans-serif; letter-spacing: .16em; }
.problem-entry h3 { margin: auto 0 1.25rem; font: 400 clamp(1.75rem,2.6vw,3rem)/1.12 STSong,"Noto Serif SC",serif; letter-spacing: -.035em; }
.problem-entry h2 { margin: auto 0 1.25rem; font: 400 clamp(1.75rem,2.6vw,3rem)/1.12 STSong,"Noto Serif SC",serif; letter-spacing: -.035em; }
.problem-entry p { min-height: 3.5em; margin: 0; color: var(--muted); font-size: .78rem; line-height: 1.75; }
.problem-entry strong { margin-top: 2rem; padding-top: 1rem; border-top: 1px solid var(--line); font-size: .66rem; letter-spacing: .08em; }
.problem-entry:last-child:nth-child(odd) { grid-column: 1 / -1; grid-template-columns: minmax(0,1.35fr) minmax(22rem,.65fr); min-height: 36rem; }
.problem-entry:last-child:nth-child(odd) figure { height: 36rem; min-height: 0; }
a.problem-entry:hover figure img { transform: scale(1.035); }
a.problem-entry:hover strong { color: var(--sage-dark); }
.problem-entry:not(.problem-entry--ready) strong { color: #92978f; font-weight: 500; }

/* 单独答案页 */
.problem-article { padding: 8.5rem var(--edge) 0; }
.article-breadcrumb { display: flex; gap: .7rem; width: var(--page); margin: 0 auto 3.2rem; color: var(--muted); font-size: .66rem; letter-spacing: .08em; }
.article-breadcrumb a { text-decoration: none; }
.article-hero { display: grid; grid-template-columns: minmax(0,1.15fr) minmax(18rem,.85fr); gap: clamp(2rem,7vw,8rem); align-items: end; width: var(--page); margin: 0 auto 3.5rem; }
.article-hero > p { grid-column: 1 / -1; margin: 0; color: var(--rust); font: 700 .65rem/1.5 Arial,sans-serif; letter-spacing: .18em; }
.article-hero h1 { margin: 0; font: 400 clamp(3.6rem,6.3vw,6.7rem)/.98 STSong,"Noto Serif SC",serif; letter-spacing: -.065em; }
.article-hero > strong { padding: 1.5rem 0 .25rem; border-top: 1px solid var(--ink); font: 400 clamp(1.05rem,1.65vw,1.55rem)/1.6 STSong,"Noto Serif SC",serif; }
.article-hero-image { position: relative; width: var(--page); height: clamp(28rem,56vw,48rem); margin: 0 auto; overflow: hidden; background: #d7d4cd; }
.article-hero-image > img { width: 100%; height: 100%; object-fit: cover; object-position: center 58%; }
.article-hero-image figcaption { position: absolute; right: 1.1rem; bottom: 1.1rem; left: 1.1rem; display: flex; justify-content: space-between; gap: 1rem; padding: .9rem 1rem; color: white; background: rgba(20,29,24,.78); backdrop-filter: blur(8px); }
.article-hero-image figcaption span { font-size: .65rem; letter-spacing: .1em; }
.article-hero-image figcaption small { color: rgba(255,255,255,.72); font-size: .58rem; }

.article-body { width: min(68rem,calc(100vw - 2 * var(--edge))); margin: 0 auto; padding: clamp(3rem,7vw,7rem) 0 1rem; }
.article-section { display: grid; grid-template-columns: 12rem minmax(0,1fr); gap: clamp(2rem,7vw,7rem); padding: clamp(3rem,5vw,5rem) 0; border-top: 1px solid var(--line); }
.article-section > header { display: flex; gap: 1rem; align-items: baseline; }
.article-section > header span { color: var(--rust); font: 700 .62rem/1 Arial,sans-serif; }
.article-section h2 { margin: 0; font: 400 clamp(1.6rem,2.3vw,2.5rem)/1.15 STSong,"Noto Serif SC",serif; }
.article-section p { margin: 0; color: var(--muted); font-size: .84rem; line-height: 1.9; }
.article-lead { color: var(--ink) !important; font: 400 clamp(1.35rem,2.2vw,2.1rem)/1.65 STSong,"Noto Serif SC",serif !important; }
.cause-list, .repair-list { display: grid; margin: 0; padding: 0; list-style: none; }
.cause-list li { display: grid; grid-template-columns: 13rem 1fr; gap: 2rem; padding: 1.6rem 0; border-bottom: 1px solid var(--line); }
.cause-list li:first-child { padding-top: 0; }
.cause-list b, .repair-list b { font-size: .9rem; letter-spacing: .03em; }
.repair-list li { display: grid; grid-template-columns: 3.25rem 1fr; gap: 1.25rem; padding: 1.5rem 0; border-bottom: 1px solid var(--line); }
.repair-list li:first-child { padding-top: 0; }
.repair-list li > span { display: grid; place-items: center; width: 2.3rem; height: 2.3rem; color: var(--white); border-radius: 50%; background: var(--sage-dark); font: 600 .7rem/1 Arial,sans-serif; }
.repair-list li div { display: grid; gap: .55rem; }

.solution-product { display: grid; grid-template-columns: minmax(0,1.08fr) minmax(28rem,.92fr); width: var(--page); margin: clamp(5rem,8vw,8rem) auto 0; border: 1px solid var(--line); background: #e2e9df; }
.solution-product > figure { min-height: 38rem; margin: 0; overflow: hidden; }
.solution-product > figure img { width: 100%; height: 100%; object-fit: cover; }
.solution-product__copy { display: flex; flex-direction: column; padding: clamp(2.5rem,4.5vw,4.5rem); }
.solution-product__copy > p:first-child { margin: 0 0 2rem; color: var(--sage-dark); font: 700 .61rem/1.5 Arial,sans-serif; letter-spacing: .16em; }
.solution-product__copy h2 { margin: 0; font: 400 clamp(2.3rem,3.8vw,4.2rem)/1.08 STSong,"Noto Serif SC",serif; letter-spacing: -.05em; }
.solution-product__copy > p:not(:first-child) { margin: 1.8rem 0 0; color: #47534c; font-size: .8rem; line-height: 1.9; }
.solution-product__pack { display: grid; grid-template-columns: 8rem 1fr; gap: 1.4rem; align-items: center; margin-top: auto; padding-top: 2rem; }
.solution-product__pack img { width: 100%; max-height: 9rem; object-fit: contain; }
.solution-product__pack div { display: grid; gap: .45rem; }
.solution-product__pack b { font: 400 1.5rem/1.2 STSong,"Noto Serif SC",serif; }
.solution-product__pack span { color: var(--muted); font-size: .7rem; }
.solution-product__pack a { width: max-content; margin-top: .65rem; padding-bottom: .25rem; border-bottom: 1px solid currentColor; font-size: .66rem; text-decoration: none; }
.technical-evidence { margin-top: 2rem; border-top: 1px solid var(--line); }
.technical-evidence summary { padding: 1.2rem 0; font-size: .69rem; font-weight: 700; letter-spacing: .08em; cursor: pointer; }
.technical-evidence dl { display: grid; grid-template-columns: repeat(2,1fr); margin: 0; border-top: 1px solid var(--line); border-left: 1px solid var(--line); }
.technical-evidence dl div { padding: 1rem; border-right: 1px solid var(--line); border-bottom: 1px solid var(--line); }
.technical-evidence dt { color: var(--muted); font-size: .61rem; }
.technical-evidence dd { margin: .45rem 0 0; font: 400 1.1rem/1.4 STSong,"Noto Serif SC",serif; }
.technical-evidence > p { margin: 1rem 0 0; color: var(--muted); font-size: .65rem; line-height: 1.7; }

.article-warning { display: grid; grid-template-columns: 10rem 1fr; gap: 2rem; width: var(--page); margin: 0 auto; padding: 1.5rem 2rem; color: white; background: var(--ink); }
.article-warning b { color: var(--acid); font-size: .66rem; letter-spacing: .1em; }
.article-warning p { margin: 0; color: rgba(255,255,255,.76); font-size: .72rem; line-height: 1.7; }
.article-return { display: flex; justify-content: space-between; width: var(--page); margin: 0 auto; padding: 2rem 0 clamp(5rem,8vw,8rem); }
.article-return a { padding-bottom: .35rem; border-bottom: 1px solid var(--ink); font-size: .7rem; text-decoration: none; }

/* 四类材料入口 */
.material-directory { display: grid; grid-template-columns: repeat(2,minmax(0,1fr)); width: var(--page); margin: 0 auto; border-top: 1px solid var(--line); border-left: 1px solid var(--line); }
.material-entry { --material-accent: var(--sage-dark); display: grid; grid-template-rows: minmax(24rem,1.25fr) minmax(19rem,.75fr); min-width: 0; min-height: 44rem; color: var(--ink); border-right: 1px solid var(--line); border-bottom: 1px solid var(--line); background: var(--white); text-decoration: none; }
.material-entry--art { --material-accent: #83516c; }
.material-entry--graph { --material-accent: #69ad87; }
.material-entry--poly { --material-accent: #657a52; }
.material-entry figure { min-height: 0; margin: 0; overflow: hidden; background: #d5d2cb; }
.material-entry figure img { width: 100%; height: 100%; object-fit: cover; transition: transform .8s cubic-bezier(.22,1,.36,1); }
.material-entry > div { display: grid; grid-template-columns: 1fr auto; grid-template-rows: auto 1fr auto; gap: 1.2rem 2rem; padding: clamp(1.8rem,3.3vw,3.5rem); }
.material-entry span { grid-column: 1 / -1; color: var(--material-accent); font: 700 .62rem/1.4 Arial,sans-serif; letter-spacing: .18em; }
.material-entry h2 { align-self: end; margin: 0; font: 400 clamp(2.7rem,4.7vw,5.2rem)/.98 STSong,"Noto Serif SC",serif; letter-spacing: -.06em; }
.material-entry p { align-self: end; max-width: 22rem; margin: 0; color: var(--muted); font-size: .8rem; line-height: 1.8; }
.material-entry strong { grid-column: 1 / -1; padding-top: 1.1rem; border-top: 1px solid var(--line); font-size: .68rem; letter-spacing: .08em; }
.material-entry:hover figure img { transform: scale(1.025); }
.material-entry:hover strong { color: var(--material-accent); }

.material-problem-page { padding-top: 8.5rem; }
.material-problem-page > .article-breadcrumb { margin-bottom: clamp(3rem,5vw,5rem); }
.material-problem-hero { margin-bottom: clamp(3rem,5vw,5rem); }
.directory-return { display: flex; justify-content: space-between; width: var(--page); margin: 0 auto; padding: 2.5rem 0 0; }
.directory-return a { padding-bottom: .35rem; border-bottom: 1px solid currentColor; font-size: .7rem; text-decoration: none; }

.knowledge-loading, .knowledge-error { width: var(--page); margin: 12rem auto 8rem; }
.knowledge-error { min-height: 50vh; }
.knowledge-error h1 { margin: 0 0 1rem; font: 400 clamp(2.8rem,6vw,6rem)/1 STSong,"Noto Serif SC",serif; }
.knowledge-error p { color: var(--muted); }
.knowledge-error a { display: inline-block; margin-top: 2rem; font-size: .75rem; }
.article-hero h1 { max-width: 9.5em; }
.solution-product__pack-image--logo { width: 7rem !important; height: 7rem; padding: 1rem; object-fit: contain !important; border-radius: 50%; background: white; }
.technical-sources { display: grid; gap: .6rem; margin-top: 1rem; }
.technical-sources a { width: max-content; max-width: 100%; color: var(--sage-dark); font-size: .64rem; line-height: 1.5; text-underline-offset: .25rem; }

@media (max-width: 1120px) {
  .problem-entry { grid-template-columns: 1fr; }
  .problem-entry:last-child:nth-child(odd) { grid-template-columns: 1fr; }
  .problem-entry:last-child:nth-child(odd) figure { height: 30rem; }
  .problem-entry figure { min-height: 20rem; }
  .problem-entry h3 { margin-top: 2.5rem; }
  .solution-product { grid-template-columns: 1fr 1fr; }
  .material-entry { grid-template-rows: minmax(20rem,1fr) minmax(20rem,auto); }
}

@media (max-width: 780px) {
  .site-header { min-height: 4.7rem; }
  .problem-index { padding-top: 7.5rem; }
  .problem-index__hero, .article-hero { grid-template-columns: 1fr; gap: 1.5rem; }
  .problem-index__hero > p, .article-hero > p { grid-column: auto; }
  .problem-index__hero h1, .article-hero h1 { font-size: clamp(3rem,14vw,4.7rem); }
  .problem-directory { grid-template-columns: 1fr; }
  .material-directory { grid-template-columns: 1fr; }
  .material-entry { grid-template-rows: 22rem auto; min-height: 0; }
  .material-entry > div { grid-template-columns: 1fr; }
  .material-entry span, .material-entry strong { grid-column: auto; }
  .material-entry h2 { font-size: clamp(3rem,14vw,4.8rem); }
  .material-entry--graph h2 { overflow-wrap: anywhere; font-size: clamp(2.65rem,12vw,4rem); }
  .problem-entry { min-height: 0; }
  .problem-entry figure { min-height: 18rem; }
  .problem-entry:last-child:nth-child(odd) figure { height: 24rem; }
  .problem-entry > div { min-height: 17rem; }
  .problem-entry h2 { margin-top: 2.5rem; }
  .problem-article { padding-top: 7rem; }
  .article-breadcrumb { margin-bottom: 2rem; overflow-x: auto; white-space: nowrap; }
  .article-hero-image { height: 58vh; min-height: 24rem; }
  .article-hero-image figcaption { display: grid; }
  .article-section { grid-template-columns: 1fr; gap: 2rem; }
  .cause-list li { grid-template-columns: 1fr; gap: .6rem; }
  .solution-product { grid-template-columns: 1fr; }
  .solution-product > figure { min-height: 25rem; }
  .solution-product__copy { min-height: 34rem; }
  .article-warning { grid-template-columns: 1fr; gap: .65rem; }
  .article-return { display: grid; gap: 1.5rem; }
  .directory-return { display: grid; gap: 1.5rem; }
  .footer-links { grid-template-columns: 1fr; gap: .85rem; justify-content: start; }
}

@media (prefers-reduced-motion: reduce) {
  * { scroll-behavior: auto !important; animation-duration: .01ms !important; transition-duration: .01ms !important; }
}