:root { color-scheme: light; font-family: Inter, Arial, "PingFang SC", "Microsoft YaHei", sans-serif; --ink:#17201d; --muted:#64716c; --line:#d8dfdc; --accent:#246b55; --soft:#eff7f3; --paper:#fff; }
* { box-sizing:border-box; }
html { scroll-behavior:smooth; }
body { margin:0; min-width:320px; color:var(--ink); background:#f5f6f5; }
a { color:inherit; }
button,input { font:inherit; }
[hidden] { display:none !important; }
.site-header { min-height:64px; display:flex; align-items:center; justify-content:space-between; gap:20px; padding:12px clamp(18px,4vw,52px); border-bottom:1px solid var(--line); background:rgba(255,255,255,.94); backdrop-filter:blur(12px); position:sticky; top:0; z-index:20; }
.site-name { font-size:20px; font-weight:800; text-decoration:none; letter-spacing:.04em; }
.site-header nav { display:flex; flex-wrap:wrap; justify-content:flex-end; gap:4px; }
.site-header nav a { padding:7px 9px; border-radius:8px; color:var(--muted); font-size:12px; text-decoration:none; }
.site-header nav a:hover,.site-header nav a[aria-current="page"] { color:var(--accent); background:var(--soft); }
.site-main { width:min(1480px,100%); margin:auto; padding:clamp(28px,5vw,68px) clamp(18px,4vw,58px) 80px; }
.hero { display:grid; grid-template-columns:minmax(0,1.4fr) minmax(260px,.6fr); gap:42px; align-items:end; margin-bottom:36px; }
.eyebrow,.kicker { margin:0 0 12px; color:var(--accent); font-size:11px; font-weight:800; letter-spacing:.15em; text-transform:uppercase; }
h1 { margin:0; font-size:clamp(40px,6vw,72px); line-height:1.04; letter-spacing:-.045em; }
.lead { max-width:830px; margin:18px 0 0; color:var(--muted); font-size:17px; line-height:1.8; }
.search-box { display:block; padding:16px; border:1px solid var(--line); border-radius:14px; background:var(--paper); }
.search-box span { display:block; margin-bottom:8px; color:var(--muted); font-size:12px; font-weight:700; }
.search-box input { width:100%; height:44px; padding:0 13px; border:1px solid var(--line); border-radius:9px; outline:none; background:#fff; }
.search-box input:focus { border-color:var(--accent); box-shadow:0 0 0 3px color-mix(in srgb,var(--accent) 14%,transparent); }
.stats { display:flex; flex-wrap:wrap; gap:12px; margin-bottom:34px; }
.stat { min-width:150px; padding:15px 18px; border:1px solid var(--line); border-radius:12px; background:var(--paper); }
.stat strong { display:block; color:var(--accent); font-size:24px; }
.stat span { color:var(--muted); font-size:12px; }
.filter-bar { display:flex; gap:8px; overflow-x:auto; margin:0 0 30px; padding-bottom:4px; }
.filter-button { flex:0 0 auto; padding:9px 13px; border:1px solid var(--line); border-radius:999px; color:var(--muted); background:#fff; cursor:pointer; }
.filter-button.active,.filter-button:hover { color:#fff; border-color:var(--accent); background:var(--accent); }
.subject-group { margin-top:44px; scroll-margin-top:90px; }
.group-head { display:flex; align-items:end; justify-content:space-between; gap:20px; margin-bottom:18px; padding-bottom:14px; border-bottom:1px solid var(--line); }
.group-head h2 { margin:0; font-size:clamp(27px,3vw,38px); }
.group-head p { max-width:780px; margin:8px 0 0; color:var(--muted); line-height:1.65; }
.group-head > span { flex:0 0 auto; color:var(--muted); font-size:12px; }
.module-grid { display:grid; grid-template-columns:repeat(2,minmax(0,1fr)); gap:18px; }
.learning-module { min-width:0; padding:24px; border:1px solid var(--line); border-radius:16px; background:var(--paper); }
.module-index { color:var(--accent); font-size:11px; font-weight:800; letter-spacing:.14em; }
.learning-module h3 { margin:10px 0 8px; font-size:22px; }
.module-summary { margin:0 0 18px; color:var(--muted); line-height:1.7; }
.concept-list { display:grid; gap:8px; }
.concept-detail { border-top:1px solid var(--line); }
.concept-detail summary { padding:13px 4px; font-weight:700; cursor:pointer; }
.concept-detail summary::marker { color:var(--accent); }
.concept-copy { padding:0 4px 15px; color:#46534f; font-size:13px; line-height:1.75; }
.concept-copy p { margin:0 0 8px; }
.method { margin-top:16px; padding:13px 15px; border-left:3px solid var(--accent); color:#44514c; background:var(--soft); font-size:13px; line-height:1.65; }
.empty-state { padding:50px 20px; color:var(--muted); text-align:center; }
.math-topic-page { max-width:1040px; margin:auto; padding:52px clamp(20px,5vw,72px) 90px; }
.back-link { color:var(--accent); font-size:13px; text-decoration:none; }
.math-topic-page h1 { margin:28px 0 0; color:var(--accent); font-size:clamp(38px,6vw,64px); line-height:1.08; }
.topic-meta { margin:12px 0 34px; color:var(--muted); }
.topic-section { margin-top:26px; padding:23px 25px; border:1px solid var(--line); border-left:4px solid var(--accent); background:#fff; }
.topic-section h2 { margin:0 0 12px; color:var(--accent); font-size:18px; }
.topic-section p { margin:0; color:#354841; font-size:16px; line-height:1.9; }
.topic-section.formula { background:var(--soft); }
.topic-section.warning { border-left-color:#b27828; background:#fff9ec; }
.periodic-section { margin:40px 0; padding:26px; border:1px solid var(--line); border-radius:18px; background:var(--paper); }
.periodic-section h2 { margin:0; font-size:32px; }
.periodic-controls { display:flex; flex-wrap:wrap; gap:7px; margin:18px 0; }
.element-filter { padding:7px 10px; border:1px solid var(--line); border-radius:999px; background:#fff; cursor:pointer; }
.element-filter.active,.element-filter:hover { color:#fff; border-color:var(--accent); background:var(--accent); }
.periodic-scroll { width:100%; overflow-x:auto; }
.periodic-table { min-width:1010px; display:grid; grid-template-columns:repeat(18,minmax(48px,1fr)); grid-template-rows:repeat(9,62px); gap:5px; }
.element { display:flex; flex-direction:column; justify-content:space-between; padding:5px; border:1px solid #ccd7d1; border-radius:4px; background:#f4f7f5; cursor:pointer; }
.element:hover,.element.selected { z-index:1; border-color:var(--accent); transform:scale(1.08); box-shadow:0 5px 16px #0002; }
.element.dimmed { opacity:.16; }
.element small,.element span { overflow:hidden; font-size:9px; text-overflow:ellipsis; white-space:nowrap; }
.element strong { font:700 18px Georgia,serif; }
.element[data-category="alkali"],.element[data-category="alkaline"] { background:#fff0dc; }.element[data-category="transition"] { background:#e7f1fb; }.element[data-category="post-transition"],.element[data-category="metalloid"] { background:#ebf4e5; }.element[data-category="nonmetal"] { background:#e3f5ef; }.element[data-category="halogen"] { background:#f8e9f2; }.element[data-category="noble"] { background:#eee9fb; }.element[data-category="lanthanide"],.element[data-category="actinide"] { background:#f5e9e4; }
.element-detail { display:grid; grid-template-columns:90px 1fr 1.2fr; gap:20px; align-items:center; margin-top:14px; padding:20px; border:1px solid var(--line); border-left:5px solid var(--accent); background:#fafcfb; }
.element-detail>div:first-child { display:flex; gap:8px; align-items:baseline; }.detail-symbol { color:var(--accent); font:700 42px Georgia,serif; }.detail-number { color:var(--muted); font-size:11px; }.element-detail h3 { margin:0 0 6px; }.element-detail p { margin:0; color:var(--muted); font-size:13px; }.element-detail dl { display:grid; grid-template-columns:repeat(3,1fr); gap:10px; margin:0; }.element-detail dt { color:var(--muted); font-size:10px; }.element-detail dd { margin:4px 0 0; font-size:12px; overflow-wrap:anywhere; }
footer { padding:28px; color:var(--muted); border-top:1px solid var(--line); text-align:center; font-size:12px; }
@media(max-width:920px){.hero{grid-template-columns:1fr}.module-grid{grid-template-columns:1fr}.element-detail{grid-template-columns:80px 1fr}.element-detail dl{grid-column:1/-1}}
@media(max-width:680px){.site-header{position:static;align-items:flex-start;flex-direction:column}.site-header nav{justify-content:flex-start}.site-main{padding-top:30px}.hero{gap:22px}.group-head{align-items:flex-start;flex-direction:column}.learning-module{padding:19px}.element-detail{display:block}.element-detail>*+*{margin-top:14px}.element-detail dl{grid-template-columns:1fr}.periodic-scroll{overflow:visible}.periodic-table{min-width:0;grid-template-columns:repeat(4,minmax(0,1fr));grid-template-rows:none}.element{min-height:62px;grid-row:auto!important;grid-column:auto!important}}