@import url('https://fonts.googleapis.com/css2?family=Golos+Text:wght@400;500;600;700;800&display=swap');
:root{--paper:#faf9f6;--ink:#202622;--muted:#777c74;--line:#e4e5de;--peach:#f4bea0;--sage:#dbe5d5;--lilac:#e4dff2;--yellow:#f5e9b9;--font:'Golos Text',Arial,sans-serif}*{box-sizing:border-box}body{margin:0;background:var(--paper);color:var(--ink);font:15px/1.55 var(--font)}button,input,select{font:inherit}a{color:inherit;text-decoration:none}button,a,input,select{outline-offset:5px}button{cursor:pointer}button:disabled{cursor:default}.hub-header{height:72px;max-width:1440px;margin:auto;padding:0 5vw;display:flex;align-items:center;gap:32px;border-bottom:1px solid var(--line)}.brand{display:flex;align-items:center;gap:12px;font-size:23px;font-weight:700;letter-spacing:-1px}.brand-mark{display:flex;align-items:center;justify-content:center;background:var(--ink);color:var(--paper);height:38px;width:38px;font-size:27px;border-radius:13px;position:relative}.brand-mark span{color:var(--peach);margin-top:-22px;font-size:28px}.hub-header nav{display:flex;gap:6px;margin-left:auto}.hub-header nav a{padding:10px 19px;border-radius:24px;font-size:14px;color:#74796f}.hub-header nav a:hover,.hub-header nav a.active{background:#eaece5;color:var(--ink)}.screen{border:1px solid var(--line);width:39px;height:39px;border-radius:50%;background:transparent;font-size:21px}main{max-width:1340px;padding:0 5vw;margin:auto;min-height:calc(100vh - 170px)}.eyebrow{text-transform:uppercase;letter-spacing:2px;font-size:11px;color:var(--muted);font-weight:600}.hero{display:grid;grid-template-columns:1.1fr 1fr;gap:60px;align-items:center;padding:70px 0 56px}.hero h1{font-size:clamp(40px,5.2vw,74px);font-weight:500;line-height:1.04;letter-spacing:-3.5px;margin:21px 0}.hero h1 em{font-style:normal;position:relative;white-space:nowrap}.hero h1 em:after{content:'';height:12px;position:absolute;bottom:3px;left:0;right:0;background:var(--peach);z-index:-1}.hero p{font-size:17px;max-width:420px;color:#777c74;line-height:1.7}.lab-art{position:relative;height:300px;display:flex;align-items:center;justify-content:center}.lab-art svg{width:100%;height:100%;overflow:visible}.float{animation:float 8s ease-in-out infinite}.float.slow{animation-delay:-4s;animation-duration:11s}.bubble{animation:bubble 4s ease-in-out infinite;transform-box:fill-box;transform-origin:center}.bubble.two{animation-delay:-2s}@keyframes float{50%{transform:translateY(-9px) rotate(2deg)}}@keyframes bubble{50%{transform:translateY(-12px);opacity:.5}}.section-top{display:flex;align-items:baseline;justify-content:space-between;margin:10px 0 21px;gap:16px}.section-top h2{font-size:23px;font-weight:500;letter-spacing:-.7px;margin:0}.section-top span{color:var(--muted);font-size:12px}.cards{display:grid;grid-template-columns:1.1fr 1fr 1fr;gap:18px;padding-bottom:50px}.tool-card{border:1px solid var(--line);border-radius:20px;overflow:hidden;transition:transform .25s,box-shadow .25s;background:#fdfcf9;position:relative;display:flex;flex-direction:column}.tool-card:hover{transform:translateY(-5px);box-shadow:0 13px 30px #20262209}.card-art{height:160px;position:relative;overflow:hidden;display:flex;align-items:center;justify-content:center;margin:8px;border-radius:13px;background:var(--sage)}.tool-card:nth-child(2) .card-art{background:var(--lilac)}.tool-card:nth-child(3) .card-art{background:var(--peach)}.card-copy{padding:15px 24px 27px}.card-copy small{font-size:10px;color:var(--muted);letter-spacing:1.6px}.card-copy h3{font-size:21px;font-weight:500;line-height:1.25;letter-spacing:-.7px;margin:10px 0}.card-copy p{font-size:13px;color:var(--muted);line-height:1.7;margin:0;max-width:250px}.periodic-art{display:grid;grid-template-columns:repeat(6,26px);gap:5px;transform:rotate(-9deg);filter:drop-shadow(0 10px 10px #4657401a)}.periodic-art i{height:28px;background:#ffffffb0;border-radius:4px}.periodic-art i:nth-child(4n){background:#98b58b}.periodic-art i:nth-child(3n){background:#efcb91}.formula-art{font-size:40px;letter-spacing:-2px;transform:rotate(-7deg);color:#65422e}.formula-art sub{font-size:24px}.series-art{display:flex;gap:8px;align-items:center;transform:rotate(-6deg)}.series-art b{padding:9px 13px;border:1px solid #8474a52a;border-radius:10px;background:#ffffff91;font-size:23px;font-weight:500}.series-art b:nth-child(2){transform:translateY(-14px);background:#fff}.series-art b:nth-child(3){transform:translateY(-28px)}.hub-footer{max-width:1340px;margin:10px auto 0;padding:23px 5vw 30px;display:flex;justify-content:space-between;color:var(--muted);font-size:11px;border-top:1px solid var(--line)}.page-head{padding:49px 0 28px}.page-head h1{font-size:clamp(32px,4vw,52px);font-weight:500;line-height:1.1;letter-spacing:-2px;margin:15px 0}.page-head p{color:var(--muted);font-size:16px;max-width:650px}.back-link{font-size:12px;color:var(--muted);display:inline-flex;gap:8px}.panel{background:#fffefa;border:1px solid var(--line);border-radius:20px;padding:28px;margin:0 0 24px}.lesson-grid{display:grid;grid-template-columns:1fr 1fr;gap:24px;padding-bottom:45px}.lesson-card{display:grid;grid-template-columns:1.15fr 1fr;border:1px solid var(--line);border-radius:20px;min-height:300px;overflow:hidden;background:#fffefa}.lesson-card .card-copy{align-self:center;padding:32px}.lesson-card h2{font-size:27px;font-weight:500;letter-spacing:-1px;line-height:1.18;margin:16px 0}.lesson-card p{color:var(--muted);font-size:14px}.lesson-card .card-art{height:auto;margin:9px;background:var(--sage)}.pill{display:inline-block;padding:5px 11px;border-radius:20px;background:var(--sage);font-size:11px}.lesson-card .open{display:inline-block;margin-top:22px;font-size:14px;border-bottom:1px solid var(--ink);padding-bottom:4px}.lesson-grid{grid-template-columns:1fr}.series{display:flex;gap:7px;overflow:auto;padding:20px 2px 28px}.metal{border:0;border-radius:10px;background:var(--sage);min-width:51px;padding:15px 7px;text-align:center;color:var(--ink)}.metal strong{font-size:24px;display:block;font-weight:500}.metal small{font-size:9px}.metal.noble{background:var(--lilac)}.metal.hydrogen{background:var(--yellow)}.metal.selected{box-shadow:0 0 0 2px var(--ink);transform:translateY(-5px)}.series-label{display:flex;justify-content:space-between;font-size:11px;color:var(--muted)}.detail-grid{display:grid;grid-template-columns:1fr 1fr;gap:24px}.detail-grid h2{font-size:24px;font-weight:500;letter-spacing:-.7px;margin:10px 0}.detail-grid p{color:var(--muted);line-height:1.8}.equation{font-size:clamp(21px,2.3vw,32px);padding:20px 0;font-weight:500;letter-spacing:-.7px}.tag{padding:5px 11px;background:var(--sage);border-radius:20px;font-size:12px;display:inline-block}.note{font-size:12px;color:var(--muted);padding:18px 0}.chooser{display:flex;gap:9px;flex-wrap:wrap}.chooser select,.search{border:1px solid var(--line);border-radius:10px;background:var(--paper);padding:11px 15px;color:var(--ink)}.search{min-width:240px;flex:1}.filterbar{display:flex;gap:7px;flex-wrap:wrap;margin-bottom:20px}.filterbar button{border:1px solid var(--line);background:transparent;border-radius:22px;padding:8px 16px;font-size:12px}.filterbar button.active{background:var(--ink);color:white;border-color:var(--ink)}.compound-layout{display:grid;grid-template-columns:1fr 1.1fr;gap:24px}.compound-list{max-height:510px;overflow:auto}.compound-row{display:flex;gap:20px;align-items:center;width:100%;padding:14px 12px;border:0;border-bottom:1px solid var(--line);text-align:left;background:transparent;border-radius:8px}.compound-row:hover,.compound-row.active{background:#e9ede3}.compound-row strong{font-weight:500;font-size:21px;min-width:102px}.compound-row span{font-size:13px}.compound-detail{position:sticky;top:20px;align-self:start;padding:32px;background:var(--sage);border:0}.compound-detail .big-formula{font-size:57px;font-weight:500;letter-spacing:-2px;margin:18px 0}.compound-detail h2{font-size:25px;line-height:1.2;font-weight:500}.compound-detail p{font-size:14px;line-height:1.8}.readout{background:#ffffff8a;border-radius:13px;padding:18px;margin-top:22px}.readout small{font-size:10px;letter-spacing:1px;color:var(--muted)}.readout p{margin:6px 0;font-weight:500}.sources a{border-bottom:1px solid #999}.empty{color:var(--muted);padding:20px}@media(min-width:1400px){main{padding:0 45px}.hub-header{padding:0 70px}.hub-footer{padding-left:45px;padding-right:45px}}@media(max-width:800px){.hub-header{height:72px;padding:0 22px;gap:12px}.brand{font-size:20px;gap:7px}.hub-header nav{gap:0}.hub-header nav a{font-size:12px;padding:9px 12px}.screen{display:none}.hero{padding:45px 0 30px;gap:20px}.hero h1{letter-spacing:-2px}.hero p{font-size:14px}.lab-art{height:245px}.cards{gap:11px}.card-copy{padding:12px 16px 30px}.card-copy h3{font-size:18px}.card-art{height:130px}.card-copy p{font-size:12px}.periodic-art{grid-template-columns:repeat(6,18px);gap:4px}.periodic-art i{height:20px}.series-art{gap:4px}.series-art b{font-size:18px;padding:6px 9px}.formula-art{font-size:29px}.compound-layout{grid-template-columns:1fr 1fr}.panel{padding:20px}.compound-row{gap:6px}.compound-row strong{min-width:82px;font-size:18px}.compound-row span{font-size:11px}}@media(max-width:550px){.hub-header{padding:0 15px}.brand{font-size:18px}.brand-mark{width:30px;height:30px;border-radius:10px;font-size:23px}.hub-header nav a{font-size:11px;padding:8px 10px}.hero{grid-template-columns:1fr;padding-top:34px;gap:0}.hero h1{font-size:51px}.hero p{font-size:15px}.lab-art{height:210px;margin-top:-8px}.cards{grid-template-columns:1fr}.tool-card{display:grid;grid-template-columns:130px 1fr;min-height:157px}.card-art{height:auto}.card-copy{padding:18px 14px}.card-copy h3{font-size:20px;margin:7px 0}.card-copy p{padding-right:8px}.periodic-art{grid-template-columns:repeat(6,14px);gap:3px}.periodic-art i{height:17px}.series-art{gap:3px}.series-art b{padding:4px;font-size:18px}.formula-art{font-size:25px}.section-top span{display:none}.hub-footer{gap:15px;font-size:9px}.detail-grid,.compound-layout{grid-template-columns:1fr}.compound-list{max-height:265px}.compound-detail{position:static}.lesson-card{grid-template-columns:1fr}.lesson-card .card-art{min-height:150px;grid-row:1}.lesson-card .card-copy{padding:25px}.page-head{padding-top:30px}.page-head h1{letter-spacing:-1.5px}.search{width:100%;min-width:0}.series{padding-bottom:20px}.metal{min-width:48px}.compound-row span{font-size:13px}.compound-detail .big-formula{font-size:48px}}@media(prefers-reduced-motion:reduce){*,*:before,*:after{animation:none!important;transition:none!important;scroll-behavior:auto!important}}

.series-hint{font-size:11px;color:var(--muted);margin:0 0 15px}@media(min-width:1400px){.series-hint{display:none}}

.cards{grid-template-columns:repeat(4,minmax(0,1fr))}.tool-card:nth-child(4) .card-art{background:#f1e9c8}.series{gap:4px;display:grid;grid-template-columns:repeat(21,minmax(0,1fr));overflow:auto}.metal{min-width:0;padding:13px 0;border-radius:8px}.metal strong{font-size:clamp(17px,2.1vw,27px)}.series-hint{display:none}.sol-art{display:grid;grid-template-columns:repeat(5,23px);gap:5px;transform:rotate(-7deg)}.sol-art i{width:23px;height:23px;background:#9bb88c;border-radius:4px}.sol-art .ins{background:#b4a2cf}.sol-art .low{background:#e9c38d}.sol-scroll{overflow:auto;max-height:66vh;border-radius:13px}.sol-table{width:100%;min-width:700px;border-collapse:separate;border-spacing:4px;text-align:center;font-size:13px;table-layout:fixed}.sol-table th{padding:13px 1px;font-weight:500;background:var(--paper);position:sticky;top:0;z-index:2}.sol-table th:first-child{left:0;z-index:3;width:66px}.sol-table tbody th{position:sticky;left:0;z-index:1}.sol-table button{display:block;width:100%;border:0;border-radius:6px;padding:12px 0;background:#dde8d6;color:#35512b;font-size:13px;font-weight:500}.sol-table button[data-sol=L]{background:#f3e6c2;color:#796124}.sol-table button[data-sol=I]{background:#e5def0;color:#6d568c}.sol-table button[data-sol=U]{background:#eee;color:#888}.sol-table button:hover,.sol-table button.selected{outline:2px solid var(--ink);outline-offset:-2px;filter:brightness(.97)}.sol-table .marked{background:#e8ece2}.sol-legend{display:flex;gap:20px;flex-wrap:wrap;font-size:12px;margin-bottom:20px}.sol-legend span{display:flex;gap:7px;align-items:center}.sol-legend i{width:12px;height:12px;border-radius:4px;background:#dde8d6}.sol-legend .low{background:#f3e6c2}.sol-legend .ins{background:#e5def0}.sol-legend .unknown{background:#eee}.sol-detail{display:flex;align-items:center;gap:30px;flex-wrap:wrap}.sol-detail .formula{font-size:37px;font-weight:500;min-width:130px}.sol-detail p{margin:5px 0;color:var(--muted)}.language-select{font:500 11px 'Golos Text',Arial,sans-serif!important;appearance:auto;width:auto!important;max-width:78px;flex-shrink:0;border:1px solid #dedfd7!important;border-radius:18px!important;background:transparent!important;color:#202622!important;padding:8px!important;height:36px;outline-offset:3px}.hub-header{gap:15px}.chem-header .language-select{margin-left:8px}.hub-header .language-select{order:4}
@media(max-width:1100px){.cards{grid-template-columns:repeat(2,minmax(0,1fr))}.hub-header nav a{padding-left:13px;padding-right:13px}}
@media(max-width:700px){.series{display:flex;gap:4px}.metal{flex:0 0 34px;min-width:34px}.metal strong{font-size:19px}.series-hint{display:block;margin-bottom:0}.hub-header{gap:7px}.hub-header nav a{padding:8px 10px}.language-select{max-width:63px;padding:6px!important}.sol-scroll{max-height:60vh}.sol-table{min-width:680px;font-size:12px;border-spacing:3px}.sol-table button{padding:10px 0}.chem-header .language-select{margin-left:0}.chem-header{column-gap:8px!important}}
@media(max-width:550px){.cards{grid-template-columns:1fr}.hub-header{padding:0 12px}.brand{font-size:16px}.brand-mark{width:27px;height:27px}.hub-header nav a{padding:8px 7px;font-size:10px}.hub-header .language-select{font-size:10px!important;max-width:54px;height:31px}.sol-legend{gap:10px}.sol-legend span{font-size:10px}}

.sol-detail{align-items:flex-start;gap:30px}.sol-description{flex:1;min-width:220px}.sol-description h2{font-size:27px;font-weight:500;letter-spacing:-.8px;line-height:1.2;margin:0 0 13px}.sol-description .tag{margin-bottom:12px}.sol-description p{line-height:1.7}.sol-description .sol-read{font-size:12px;color:var(--muted);margin-bottom:9px}.sol-equation{font-size:19px!important;color:var(--ink)!important;overflow-wrap:anywhere}.sol-detail .formula{padding-top:1px}.sol-description .note{padding:0;margin-top:9px;font-size:12px}@media(max-width:550px){.sol-detail{gap:18px}.sol-description{min-width:0;width:100%}.sol-description h2{font-size:24px}}

.game-empty{padding:36px;text-align:center;background:#fff;border-radius:28px;max-width:760px;margin:0 auto 60px}.game-empty .formula-art{height:100px;font-size:70px}.game-empty p{color:var(--muted,#6d736b);line-height:1.6}.game-empty .back-link{display:inline-block;margin:18px 0}