:root{--ink:#203c36;--muted:#72817c;--green:#18765c;--line:#e0e8e2;--paper:#f5f7f2}*{box-sizing:border-box}body{margin:0;background:var(--paper);color:var(--ink);font-family:"Nirmala UI","Segoe UI",sans-serif;font-size:14px}button,input,select{font:inherit}button,select{cursor:pointer}button,a,input,select{ -webkit-tap-highlight-color:transparent}button{color:inherit}button:focus-visible,a:focus-visible,input:focus-visible,select:focus-visible{outline:3px solid #dcaa3a;outline-offset:3px}button:disabled{opacity:.45;cursor:not-allowed}a{color:var(--green)}header{height:92px;padding:0 5%;display:flex;align-items:center;justify-content:space-between;background:#fff;border-bottom:1px solid var(--line)}.brand{display:flex;gap:12px;align-items:center;text-decoration:none;color:var(--ink);font-size:25px;font-weight:750}.brand-icon{font-family:Georgia;font-size:38px;background:var(--green);color:#fff;width:49px;height:49px;border-radius:15px;text-align:center}.brand small{display:block;font:9px "Segoe UI",sans-serif;letter-spacing:2px;margin-top:2px}.tab{border:0;background:none;padding:15px 22px;color:var(--muted);border-radius:9px}.tab.active{background:#eaf3ed;color:var(--green);font-weight:650}.level{font-size:12px}.level i,.live i{display:inline-block;width:6px;height:6px;border-radius:50%;background:#4f9d72;margin-right:6px}main{max-width:1440px;margin:auto;padding:38px 5% 0}.intro{display:flex;align-items:center;justify-content:space-between;margin-bottom:36px}.eyebrow{font-size:11px;letter-spacing:1px;color:var(--green);font-weight:650}h1{font-size:36px;font-weight:650;margin:10px 0}h1 em{font-style:normal;color:var(--green)}p{line-height:1.8}.intro p{color:var(--muted);margin:0}.stats{display:flex;gap:34px}.stats b{font-size:28px;font-weight:500;border-left:1px solid var(--line);padding-left:30px}.stats span{display:block;font-size:11px;color:var(--muted);font-weight:400;margin-top:5px}.layout{display:grid;grid-template-columns:265px minmax(0,1fr);gap:28px}.catalog{background:#fff;border:1px solid var(--line);border-radius:15px;padding:22px 17px;align-self:start}.section-top{display:flex;justify-content:space-between;align-items:center;gap:8px}h2,h3{margin:0}h2{font-size:18px}h3{font-size:14px;font-weight:600}.section-top>span{font-size:12px;color:var(--muted)}.search{display:flex;align-items:center;gap:8px;border:1px solid var(--line);border-radius:8px;margin:21px 0 17px;padding:9px;color:var(--muted);font-size:22px}.search input{width:100%;min-width:0;background:none;border:0;outline:none;font-size:12px;color:var(--ink)}.filter-label{font-size:11px;color:var(--muted);display:block;margin-bottom:6px}select{border:1px solid var(--line);background:white;border-radius:6px;padding:8px;color:var(--ink)}#category{width:100%;font-size:12px}.reaction-list{margin-top:16px;max-height:620px;overflow:auto;scrollbar-width:thin}.reaction-item{display:block;text-align:left;width:100%;border:1px solid transparent;border-radius:9px;background:none;padding:13px 11px;margin-bottom:5px}.reaction-item:hover{background:#f4f8f4}.reaction-item.selected{background:#edf5ee;border-color:#bcd6c4}.reaction-item .item-top{display:flex;gap:9px;align-items:center}.number{font:11px monospace;color:#8b9f92}.reaction-item strong{font-size:12px;font-weight:600}.reaction-item small{display:block;color:var(--muted);font:11px "Segoe UI",sans-serif;margin:7px 0 0 25px}.aside-note{display:flex;gap:12px;align-items:center;background:#faf8ed;border-radius:8px;margin-top:20px;padding:10px 13px;color:#8c7e46}.aside-note span{font-size:26px}.aside-note p{font-size:11px;margin:0}#workspace{min-width:0}.workspace-heading{display:flex;justify-content:space-between;align-items:center;margin:3px 0 22px}.workspace-heading h2{font-size:23px;margin-top:6px}.chip{padding:6px 12px;border-radius:20px;background:#e7eee1;color:#63804a;font-size:11px}.ingredients,.explanation{background:white;border:1px solid var(--line);border-radius:12px;padding:20px}.text-button{border:0;background:transparent;color:var(--green);font-size:11px;padding:4px}.ingredients #reagents{display:flex;gap:12px;margin:17px 0}.reagent{flex:1;border:1px solid var(--line);border-radius:9px;background:#fcfdfa;display:flex;align-items:center;text-align:left;padding:12px;gap:13px}.reagent.added{background:#edf5ee;border-color:#8eb9a2}.formula-icon{font-family:"Segoe UI",sans-serif;color:var(--green);font-size:19px;min-width:48px;font-weight:600}.reagent small{display:block;font:10px "Segoe UI",sans-serif;color:var(--muted);margin-top:5px}.reagent .add{margin-left:auto;font-size:19px;color:var(--green)}.condition{font-size:11px;background:#f5f6f0;border-radius:6px;padding:8px 11px;margin:0;color:#6e7968}.scenes{display:grid;grid-template-columns:1fr 1fr;gap:17px;margin-top:18px}.scene{border-radius:12px;border:1px solid var(--line);overflow:hidden;background:#fff;position:relative}.scene-heading{display:flex;justify-content:space-between;align-items:center;padding:17px}.scene-heading h3{font-size:12px}.live,.tiny-tag{font-size:9px;color:var(--muted)}.particle-scene{background-color:#f0f5f0;background-image:radial-gradient(#ccd9ce .7px,transparent .7px);background-size:15px 15px}.scene svg{display:block;width:100%;height:255px}.scene-caption{text-align:center;font-size:11px;margin:0;min-height:49px;padding:9px 15px;color:#63786c}.controls{display:flex;gap:10px;align-items:center;flex-wrap:wrap;background:#fff;padding:17px;border:1px solid var(--line);border-radius:10px;margin-top:18px}.primary,.secondary{border:0;border-radius:7px;padding:11px 16px;font-size:12px;font-weight:600}.primary{background:var(--green);color:white;box-shadow:0 3px 5px #18765c15}.primary:hover{background:#125e48}.secondary{background:#f0f4ef;border:1px solid var(--line)}.controls label{font-size:10px;color:var(--muted);display:flex;align-items:center;gap:7px}.controls select{font-size:11px;padding:6px}.motion{margin-left:auto}.timeline{height:4px;background:#eaf0e9;width:100%;border-radius:4px;margin-top:5px;overflow:hidden}#timelineFill{background:var(--green);height:100%;width:0}.steps{display:flex;justify-content:space-between;font-size:10px;color:#87958a;margin:12px 0 22px;padding:0 12px}.steps .current{color:var(--green);font-weight:700}.equation{text-align:center;font-family:"Segoe UI",sans-serif;font-size:22px;padding:23px 10px;background:#f6f8f3;border-radius:8px;margin-top:16px;overflow-wrap:anywhere}.explanation>p{font-size:12px;color:#63786c;margin:14px 0}.explanation-footer{border-top:1px solid var(--line);padding-top:12px;display:flex;justify-content:space-between;gap:15px;font-size:9px;color:var(--muted)}.model-note{color:var(--muted);font-size:10px;margin:16px 4px}.quiz-panel{padding:20px;border:1px solid #dfd6aa;background:#fffbed;border-radius:12px;margin-bottom:18px}.quiz-panel p{font-size:13px}#answers{display:flex;gap:9px;flex-wrap:wrap}#answers button{background:#fff;border:1px solid #d6d9cc;padding:10px;border-radius:6px}#answers button.correct{background:#e3f3e5;border-color:var(--green)}#answers button.wrong{background:#fce5dc;border-color:#b55b36}#feedback{color:var(--green)}.mix-check{background:#edf2e9;border:1px solid var(--line);padding:25px;border-radius:12px;margin-top:34px;display:flex;flex-wrap:wrap;align-items:center;justify-content:space-between;gap:20px}.mix-check h2{font-size:17px}.mix-check p{margin:5px 0 0;color:var(--muted);font-size:11px}.mix-check form{display:flex;gap:10px;align-items:end}.mix-check label{font-size:10px}.mix-check select{display:block;max-width:150px;margin-top:6px}.mix-check #mixResult{width:100%;margin:0;color:var(--green)}footer{display:flex;justify-content:space-between;padding:25px 0;margin-top:15px;color:#86928a;font-size:10px}footer>span:first-child{font-size:16px;color:var(--green)}.skip{position:absolute;left:8px;top:-100px;background:white;padding:10px;z-index:5}.skip:focus{top:8px}[hidden]{display:none!important}sub{font-size:.65em}.empty{padding:15px;color:var(--muted)}@media(min-width:1400px){main{padding-left:3%;padding-right:3%}}@media(max-width:1000px){.layout{grid-template-columns:220px minmax(0,1fr);gap:18px}.scene-heading{padding:12px}.scene-heading h3{font-size:10px}.stats{gap:15px}.stats b{padding-left:15px}.reagent{flex-wrap:wrap}.reagent small{max-width:120px}.controls{gap:8px}.motion{margin-left:0}.equation{font-size:18px}}@media(max-width:750px){header{height:auto;min-height:80px;flex-wrap:wrap;padding:16px 5%;gap:16px}.brand{font-size:21px}.brand-icon{width:40px;height:40px;font-size:30px}.level{display:none}.tab{padding:10px;font-size:12px}main{padding-top:25px}.intro{align-items:start;gap:10px}h1{font-size:27px}.intro p{font-size:12px}.stats{display:none}.layout{display:block}.catalog{padding:15px;margin-bottom:24px}.catalog .search{margin:13px 0}.reaction-list{display:flex;max-height:none;overflow-x:auto;margin-top:12px}.reaction-item{min-width:200px;max-width:200px}.aside-note{display:none}.workspace-heading h2{font-size:20px}.scene svg{height:220px}.scene-caption{min-height:65px}.mix-check form{flex-wrap:wrap}.mix-check select{max-width:130px}.explanation-footer{flex-wrap:wrap}}@media(max-width:450px){.scenes{grid-template-columns:1fr}.scene svg{height:230px}.scene-caption{min-height:42px}.ingredients #reagents{flex-direction:column}.reagent{flex-wrap:nowrap}.reagent small{max-width:none}.workspace-heading{gap:10px}.chip{white-space:nowrap}.intro h1{font-size:25px}.equation{font-size:17px}footer{gap:16px}}@media(prefers-reduced-motion:reduce){*{scroll-behavior:auto!important}}

.dev-credit a{color:var(--green);text-decoration:none;font-weight:600}.dev-credit a:hover{text-decoration:underline}
footer.site-footer{flex-wrap:wrap;align-items:center;gap:12px 20px}
.site-footer .dev-credit{flex-basis:100%;order:5;text-align:center;font-size:12px;line-height:1.8;color:#60756a;padding-top:14px;border-top:1px solid var(--line)}
.site-footer .dev-credit a{display:inline;min-height:0;padding:0;white-space:nowrap}

/* Shared touch navigation; progressively enhanced by common.js. */
.mobile-menu-toggle{display:none}
summary:focus-visible{outline:3px solid #dcaa3a;outline-offset:3px}
@media(max-width:760px){
 header.has-mobile-menu{height:auto;min-height:78px;padding:14px 4%;gap:12px;display:flex;flex-wrap:wrap}
 header.has-mobile-menu .brand{font-size:21px;min-width:0}
 header.has-mobile-menu .brand small{font-size:8px;letter-spacing:1px}
 header.has-mobile-menu .brand-icon{width:40px;height:40px;font-size:30px;flex-shrink:0}
 header.has-mobile-menu .mobile-menu-toggle{display:inline-flex;align-items:center;justify-content:center;order:2;margin-left:auto;min-height:44px;padding:8px 12px;border:1px solid #cadbd0;border-radius:9px;background:#f2f7f2;font-size:12px;color:#245a44}
 header.has-mobile-menu .child-toggle{order:4;width:100%;min-height:32px;margin:0;font-size:12px;justify-content:flex-start}
 header.has-mobile-menu nav{display:none!important;order:3;flex:1 0 100%;width:100%;padding:8px 0;border-top:1px solid var(--line)}
 header.has-mobile-menu.menu-open nav{display:grid!important;grid-template-columns:repeat(2,minmax(0,1fr));gap:6px}
 header.has-mobile-menu nav a{min-height:44px;white-space:normal;text-align:center;justify-content:center;padding:10px;font-size:12px;border-radius:8px}
}

/* ---- Site header: one sticky bar on every page except the subject picker (built in common.js) ---- */
body header.site-header{position:sticky;top:0;z-index:60;height:auto;min-height:0;display:flex;flex-wrap:nowrap;align-items:center;gap:18px;padding:10px max(4%,calc((100% - 1240px)/2));background:rgba(255,255,255,.96);backdrop-filter:saturate(1.4) blur(8px);border-bottom:1px solid var(--line);box-shadow:0 2px 12px #203c360a}
body header.site-header .brand{font-size:20px;gap:10px;flex-shrink:0}
body header.site-header .brand-icon{width:40px;height:40px;font-size:30px;line-height:40px;border-radius:12px}
body header.site-header .brand small{font-size:8px;letter-spacing:1.5px}
body header.site-header nav{order:0;flex:1 1 auto;min-width:0;width:auto;display:flex;flex-wrap:nowrap;gap:4px;justify-content:flex-start;overflow-x:auto;scrollbar-width:none;padding:2px}
body header.site-header nav::-webkit-scrollbar{display:none}
body header.site-header nav .tab{flex:0 0 auto;display:inline-flex;align-items:center;gap:7px;min-height:40px;padding:8px 14px;border-radius:999px;font-size:13.5px;color:#4f625b;text-decoration:none;white-space:nowrap;text-align:left;transition:background .15s,color .15s}
body header.site-header nav .tab:hover{background:#eef5f0;color:var(--green)}
body header.site-header nav .tab.active{background:var(--green);color:#fff;font-weight:650}
body header.site-header nav .subject-home{font-weight:650;color:var(--ink);box-shadow:inset 0 0 0 1px var(--line)}
body header.site-header nav .subject-home.active{box-shadow:none}
.tab-icon{font-size:.95em;line-height:1}
.header-actions{display:flex;align-items:center;gap:8px;flex-shrink:0}
.subject-switch-link{display:inline-flex;align-items:center;gap:6px;min-height:38px;padding:7px 13px;border:1px solid var(--line);border-radius:999px;background:#fff;color:var(--ink);text-decoration:none;font-size:12.5px;white-space:nowrap}
.subject-switch-link:hover{border-color:var(--green);color:var(--green)}
body header.site-header .child-toggle{display:inline-flex;align-items:center;gap:7px;width:auto;min-height:38px;margin:0;padding:6px 13px;border-radius:999px;background:#eef5f0;color:#2f5a48;font-size:12.5px;white-space:nowrap;cursor:pointer}
body header.site-header .child-toggle input{accent-color:var(--green);width:16px;height:16px;margin:0}
body header.site-header a:focus-visible,body header.site-header button:focus-visible,body header.site-header .child-toggle:focus-within{outline:3px solid #dcaa3a;outline-offset:2px}
/* Medium screens: the tabs get their own scrollable row under the brand. */
@media(max-width:1180px){
 body header.site-header{flex-wrap:wrap;row-gap:6px}
 body header.site-header .header-actions{margin-left:auto}
 body header.site-header nav{order:3;flex:1 0 100%}
}
/* Phones: brand and a menu button; the menu opens as a grid of large buttons with the settings below. */
@media(max-width:760px){
 body header.site-header{gap:10px;padding:9px 4%}
 body header.site-header .brand{font-size:19px}
 body header.site-header .mobile-menu-toggle{display:inline-flex;align-items:center;gap:6px;order:2;margin-left:auto;min-height:44px;padding:8px 14px;border:1px solid #cadbd0;border-radius:12px;background:#f2f7f2;color:#245a44;font-size:13px;font-weight:600}
 body header.site-header nav,body header.site-header .header-actions{display:none}
 body header.site-header.menu-open nav{display:grid;order:3;flex:1 0 100%;grid-template-columns:1fr 1fr;gap:8px;overflow:visible;padding:10px 0 4px;border-top:1px solid var(--line)}
 body header.site-header.menu-open nav .tab{justify-content:flex-start;min-height:52px;padding:10px 14px;border-radius:14px;background:#f5f9f6;font-size:14px;white-space:normal}
 body header.site-header.menu-open nav .tab.active{background:var(--green)}
 body header.site-header.menu-open nav .subject-home{grid-column:1/-1}
 body header.site-header.menu-open .header-actions{display:flex;order:4;flex:1 0 100%;justify-content:space-between;flex-wrap:wrap;gap:8px;padding:6px 0 8px}
 body header.site-header.menu-open .header-actions>*{flex:1 1 45%;justify-content:center;min-height:44px}
}

/* ---- Site footer: the same three columns on every page ---- */
footer.site-footer{display:block;margin:56px 0 0;padding:0 0 28px;border:0;font-size:13px;color:#4f625b}
.site-footer-inner{display:grid;grid-template-columns:1.5fr 1fr 1fr;gap:28px 36px;padding:28px 30px;background:#fff;border:1px solid var(--line);border-radius:18px}
.footer-brand{display:inline-flex;align-items:center;gap:10px;color:var(--ink);text-decoration:none;font-size:20px;font-weight:750}
.footer-brand .brand-icon{width:36px;height:36px;font-size:26px;line-height:36px;border-radius:11px}
.footer-about p{margin:12px 0 0;line-height:1.8;max-width:36ch}
.footer-about .footer-note{font-size:12px;color:#72817c}
.footer-column h2{margin:4px 0 10px;font-size:13px;letter-spacing:.5px;color:var(--ink)}
.footer-column ul{list-style:none;margin:0;padding:0;display:grid;gap:2px}
.footer-column a{display:inline-flex;align-items:center;gap:6px;min-height:34px;color:#3f5a50;text-decoration:none}
.footer-column a:hover{color:var(--green);text-decoration:underline}
.site-footer-bottom{display:flex;flex-wrap:wrap;align-items:center;justify-content:space-between;gap:10px 18px;padding:16px 6px 0;font-size:12px;color:#72817c}
.footer-top{border:1px solid var(--line);background:#fff;border-radius:999px;padding:8px 14px;min-height:38px;color:var(--green);font-size:12px}
.footer-top:hover{border-color:var(--green)}
.site-footer .dev-credit{flex-basis:auto;order:0;border:0;padding:0;text-align:right;font-size:12px}
@media(max-width:760px){
 .site-footer-inner{grid-template-columns:1fr 1fr;padding:22px 18px}
 .footer-about{grid-column:1/-1}
 .site-footer-bottom{flex-direction:column;align-items:flex-start}
 .site-footer .dev-credit{text-align:left}
}
/* Chapter lists: a little space between "পাঠ ১" and the lesson link. */
.chapter-lessons .chapter-no{margin-right:.5em}
/* Page stylesheets (home.css) restyle bare footer text; keep the footer's own sizes everywhere. */
footer.site-footer .footer-about p{font-size:13px}footer.site-footer .footer-about .footer-note{font-size:12px}
footer.site-footer .footer-column a{font-size:13px}footer.site-footer .site-footer-bottom span{font-size:12px}

/* ---- Page polish ---- */
/* Link-buttons never carry the link underline. */
a.primary,a.secondary{text-decoration:none}
/* Tabs that do not fit beside the brand get their own row (set by common.js). */
@media(min-width:761px){body header.site-header.nav-crowded{flex-wrap:wrap;row-gap:6px}body header.site-header.nav-crowded .header-actions{margin-left:auto}body header.site-header.nav-crowded nav{order:3;flex:1 0 100%}}
/* ---- Ad blocks (public/ad-slots.js, placed by public/ad-blocks.js) and the footer partner link ---- */
.ad-slot{display:block;max-width:728px;min-height:90px;margin:20px auto;padding:8px 10px 10px;border:1px solid var(--line);border-radius:12px;background:#fbfcf9;text-align:center;overflow:hidden}
.ad-slot .ad-label{display:block;font-size:10px;letter-spacing:1px;color:#8a9a92;margin-bottom:6px;text-align:left}
.ad-slot .ad-body{display:grid;place-items:center;min-height:60px;overflow:hidden}
.ad-slot.ad-preview{border:2px dashed #dcaa3a;background:#fffaf0}
.ad-slot.ad-preview .ad-body{color:#9a6c12;font-size:13px;font-weight:600}
@media(max-width:600px){.ad-slot{max-width:none;min-height:100px;margin:16px 0}}
.ad-slot.ad-slot-side{margin:16px 0 0;min-height:0}
/* The site notice from the admin panel (placed by public/ad-blocks.js). */
.site-notice{display:flex;align-items:flex-start;gap:12px;margin:0 0 16px;padding:10px 14px;border:1px solid #b9d8c6;border-radius:12px;background:#eaf6ef;color:#1d4a3a}
.site-notice p{margin:0;flex:1;line-height:1.7}.site-notice a{font-weight:700;color:inherit}
.site-notice-warning{border-color:#efc58a;background:#fff4e2;color:#6b4210}
.site-notice-close{border:0;background:none;font-size:16px;line-height:1;padding:4px;cursor:pointer;color:inherit}
.partner-link{font-size:12px;color:#72817c}.partner-link a{color:var(--green);font-weight:600;text-decoration:none}.partner-link a:hover{text-decoration:underline}