:root{--bg:#f7f5f0;--paper:#fffefa;--ink:#262a2a;--muted:#6d7471;--line:#dddcd5;--accent:#df4f20;--accent-soft:#fff0e9;--green:#276d57;--green-soft:#e8f3ed;--shadow:0 18px 60px rgba(31,35,31,.06);font-family:Inter,"PingFang SC","Microsoft YaHei",system-ui,sans-serif;color:var(--ink);background:var(--bg)}
*{box-sizing:border-box}html{scroll-behavior:smooth}body{margin:0}button,input,select,textarea{font:inherit}button{cursor:pointer}button:disabled{cursor:not-allowed;opacity:.5}a{color:var(--accent)}:focus-visible{outline:3px solid #f0a78d;outline-offset:2px}.loading{padding:30vh 1rem;text-align:center;color:var(--muted)}
.shell{max-width:1180px;margin:auto;padding:0 24px}.site-header{position:sticky;top:0;z-index:20;background:rgba(247,245,240,.94);backdrop-filter:blur(16px);border-bottom:1px solid var(--line)}.header-inner{min-height:70px;display:flex;align-items:center;justify-content:space-between;gap:24px}.brand{display:flex;align-items:center;gap:10px;border:0;background:none;color:var(--ink);padding:0;text-align:left}.brand-mark{width:34px;height:34px;display:grid;place-items:center;border-radius:10px;background:var(--ink);color:white;font-size:23px;line-height:1}.brand-name{font-family:Georgia,"Songti SC",serif;font-size:20px;font-weight:700;white-space:nowrap}.brand-name small{font:500 11px Inter,system-ui,sans-serif;letter-spacing:.06em;color:var(--muted)}.nav{display:flex;gap:5px}.nav button{border:0;background:transparent;color:var(--muted);padding:9px 14px;border-radius:999px;white-space:nowrap}.nav button:hover,.nav button.active{background:var(--ink);color:white}
main{padding-top:42px;padding-bottom:72px}.eyebrow{font-size:12px;font-weight:800;letter-spacing:.16em;text-transform:uppercase;color:var(--accent)}h1,h2,h3,p{margin-top:0}h1,h2,h3{font-family:Georgia,"Songti SC",serif}h1{font-size:clamp(42px,5vw,68px);line-height:1.08;letter-spacing:-.04em;margin:14px 0 20px}h2{font-size:clamp(27px,3vw,36px);margin-bottom:10px}h3{font-size:21px;margin-bottom:9px}.muted{color:var(--muted)}.tiny{font-size:12px}.lead{font-size:16px;line-height:1.85;color:var(--muted);max-width:690px}.hero{display:grid;grid-template-columns:minmax(0,1.6fr) minmax(250px,.7fr);align-items:center;gap:36px}.hero-card{background:var(--paper);border:1px solid var(--line);border-radius:28px;padding:24px;box-shadow:var(--shadow);transform:rotate(2deg)}.hero-card .molecule{height:210px}.hero-card p{text-align:center;color:var(--muted);margin:7px 0 0;font-size:13px}.stats{display:flex;gap:24px;flex-wrap:wrap;margin-top:30px}.stat strong{font-size:24px;font-family:Georgia,serif}.stat span{display:block;font-size:12px;color:var(--muted);margin-top:4px}
.section{margin-top:48px}.section-head{display:flex;justify-content:space-between;align-items:end;gap:16px;margin-bottom:18px}.section-head p{margin:0;color:var(--muted)}.panel{background:var(--paper);border:1px solid var(--line);border-radius:22px;padding:24px;box-shadow:var(--shadow)}.grid-2{display:grid;grid-template-columns:1fr 1fr;gap:18px}.grid-3{display:grid;grid-template-columns:repeat(3,1fr);gap:14px}.flow{display:flex;gap:10px;flex-wrap:wrap;align-items:center}.stack{display:grid;gap:14px}.divider{border:0;border-top:1px solid var(--line);margin:22px 0}.pill,.chip{border:1px solid var(--line);background:white;border-radius:999px;color:var(--ink);padding:9px 15px}.pill:hover,.chip:hover{border-color:var(--accent)}.pill.selected,.chip.selected{background:var(--ink);color:white;border-color:var(--ink)}.pill.accent.selected{background:var(--accent);border-color:var(--accent)}.btn{border:1px solid var(--line);background:white;color:var(--ink);border-radius:12px;padding:11px 17px;font-weight:650}.btn:hover{border-color:var(--accent);color:var(--accent)}.btn.primary{background:var(--accent);border-color:var(--accent);color:white}.btn.primary:hover{background:#c43f14}.btn.dark{background:var(--ink);border-color:var(--ink);color:white}.btn.small{padding:7px 11px;font-size:13px;border-radius:9px}.btn.ghost{border:0;background:transparent;padding:8px 10px}.btn.danger{color:#aa3434}.btn-row{display:flex;gap:10px;flex-wrap:wrap;align-items:center}.mode-card{display:flex;flex-direction:column;align-items:flex-start;gap:10px;min-height:175px;text-align:left;border:1px solid var(--line);background:var(--paper);border-radius:20px;padding:22px;color:var(--ink)}.mode-card:hover,.mode-card.selected{border-color:var(--accent);box-shadow:0 8px 25px rgba(223,79,32,.1)}.mode-icon{display:grid;place-items:center;width:38px;height:38px;border-radius:12px;background:var(--accent-soft);color:var(--accent);font-size:23px}.mode-card strong{font-size:19px}.mode-card span:last-child{font-size:13px;color:var(--muted);line-height:1.6}.tip{padding:15px 18px;background:#f0eee8;border-radius:13px;color:var(--muted);font-size:13px;line-height:1.7}.empty{padding:36px 20px;text-align:center;color:var(--muted);border:1px dashed var(--line);border-radius:18px}.progress{height:7px;background:#e8e7e1;border-radius:99px;overflow:hidden}.progress>span{display:block;background:var(--accent);height:100%;transition:width .2s}.quiz-layout{max-width:850px;margin:auto}.quiz-top{display:flex;justify-content:space-between;align-items:center;gap:16px;margin-bottom:18px}.quiz-question{text-align:center;padding:28px 16px}.quiz-question h1{font-size:clamp(30px,4vw,45px);letter-spacing:0;margin:10px 0}.quiz-question .molecule{height:260px;max-width:500px;margin:auto}.quiz-options{display:grid;grid-template-columns:1fr 1fr;gap:12px}.option{min-height:105px;border:1px solid var(--line);border-radius:17px;background:white;padding:13px;color:var(--ink);text-align:left;display:flex;align-items:center;gap:14px}.option:hover:not(:disabled){border-color:var(--accent);transform:translateY(-1px)}.option.selected{border-color:var(--accent)}.option.correct{border-color:var(--green);background:var(--green-soft)}.option.wrong{border-color:#be5348;background:#fff0eb}.option .letter{display:grid;place-items:center;flex:0 0 27px;width:27px;height:27px;border-radius:8px;background:#f1f0eb;font-size:12px;font-weight:800;color:var(--muted)}.option .molecule{height:120px;flex:1;min-width:0}.option .answer-text{font-weight:650;line-height:1.5}.answer-panel{margin-top:18px;padding:20px;background:var(--paper);border:1px solid var(--line);border-radius:18px}.answer-panel.good{border-color:#9bcbb1;background:var(--green-soft)}.answer-panel.bad{border-color:#edb8a5;background:#fff6f1}.answer-panel p{margin-bottom:7px;line-height:1.6}.answer-actions{display:flex;gap:8px;flex-wrap:wrap;margin-top:14px}.molecule{position:relative;display:flex;align-items:center;justify-content:center;overflow:hidden}.molecule svg{max-width:100%;max-height:100%;width:100%;height:100%}.molecule canvas{max-width:100%;max-height:100%}.molecule-fallback{font-size:12px;color:var(--muted);overflow-wrap:anywhere;text-align:center;padding:10px}.result-score{font-family:Georgia,serif;font-size:64px;line-height:1;color:var(--accent);margin:18px 0}.searchbar{width:100%;border:1px solid var(--line);border-radius:12px;padding:13px 16px;background:white;color:var(--ink)}.toolbar{display:flex;gap:12px;align-items:center;flex-wrap:wrap;margin:18px 0}.toolbar select,.form-field select,.form-field input,.form-field textarea{border:1px solid var(--line);border-radius:10px;padding:11px 12px;background:white;color:var(--ink);width:100%}.toolbar select{width:auto}.library-grid{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:15px}.library-card{background:var(--paper);border:1px solid var(--line);border-radius:18px;padding:14px;min-width:0}.library-card .molecule{height:160px;background:white;border:1px solid #f0eee8;border-radius:12px}.library-card h3{font-family:inherit;font-size:17px;margin:13px 0 4px}.library-card .subtitle{font-size:12px;color:var(--muted);min-height:18px}.library-card .note{font-size:12px;line-height:1.6;color:var(--muted);min-height:38px}.badge{display:inline-block;border-radius:5px;background:#f0eee8;color:var(--muted);font-size:11px;padding:3px 6px;margin-right:4px}.badge.orange{background:var(--accent-soft);color:var(--accent)}.card-actions{display:flex;gap:5px;flex-wrap:wrap;margin-top:11px}.card-actions button{border:1px solid var(--line);background:white;border-radius:7px;padding:5px 8px;font-size:12px;color:var(--muted)}.card-actions button:hover{color:var(--accent);border-color:var(--accent)}.pagination{display:flex;justify-content:center;gap:12px;align-items:center;margin-top:24px}.form-grid{display:grid;grid-template-columns:1fr 1fr;gap:16px}.form-field{display:grid;gap:6px;font-size:13px;font-weight:650}.form-field.wide{grid-column:1/-1}.form-field textarea{min-height:82px;resize:vertical}.preview{height:260px;border:1px dashed var(--line);background:white;border-radius:16px;margin-top:14px}.sketch-board{position:relative;height:370px;border:1px solid var(--line);background:white;border-radius:14px;overflow:hidden;touch-action:none}.sketch-board svg{display:block;width:100%;height:100%}.tool-btn{border:1px solid var(--line);border-radius:8px;background:white;padding:8px 11px;min-width:38px}.tool-btn.selected{border-color:var(--accent);background:var(--accent-soft);color:var(--accent)}.helper{font-size:12px;color:var(--muted);line-height:1.6}.footer{border-top:1px solid var(--line);padding:24px 0 36px;color:var(--muted);font-size:12px}.footer-inner{display:flex;justify-content:space-between;gap:15px;flex-wrap:wrap}.modal-wrap{position:fixed;inset:0;z-index:30;background:rgba(25,29,27,.55);display:grid;place-items:center;padding:16px}.modal{width:min(100%,560px);max-height:90vh;overflow:auto;background:var(--paper);border-radius:20px;padding:24px;box-shadow:0 24px 80px rgba(0,0,0,.2)}.modal header{display:flex;align-items:center;justify-content:space-between;gap:10px;margin-bottom:18px}.modal h2{font-size:25px;margin:0}.modal .close{border:0;background:none;font-size:25px;color:var(--muted)}.toast{position:fixed;z-index:40;left:50%;bottom:24px;transform:translateX(-50%);background:var(--ink);color:white;border-radius:10px;padding:12px 18px;box-shadow:0 9px 30px #0002;font-size:13px}
@media(max-width:800px){.hero{grid-template-columns:1fr}.hero-card{max-width:300px;transform:none}.library-grid{grid-template-columns:repeat(2,minmax(0,1fr))}.grid-3{grid-template-columns:1fr}.mode-card{min-height:130px}.nav button{padding:8px 10px}.brand-name small{display:none}}
@media(max-width:560px){.shell{padding:0 15px}.header-inner{min-height:62px;gap:6px}.brand-name{font-size:16px}.brand-mark{width:30px;height:30px}.nav{gap:0}.nav button{font-size:13px;padding:7px 8px}main{padding-top:27px}.panel{padding:17px}.section{margin-top:34px}.grid-2,.form-grid,.quiz-options{grid-template-columns:1fr}.library-grid{grid-template-columns:1fr 1fr;gap:9px}.library-card{padding:9px}.library-card .molecule{height:130px}.library-card h3{font-size:14px}.library-card .note{min-height:0}.card-actions button{font-size:11px}.quiz-question .molecule{height:210px}.option{min-height:70px}.option .molecule{height:100px}.stats{gap:18px}}

/* Brighter study workspace and new bilingual identity. */
:root{--bg:#fff;--paper:#fff;--ink:#182e2d;--muted:#637574;--line:#dce6e2;--accent:#d85631;--accent-soft:#fff1eb;--shadow:0 8px 28px rgba(16,72,65,.055);background:#fff}
.site-header{background:#fff;backdrop-filter:none;border-bottom:1px solid #e4eae7}.header-inner{min-height:82px}.brand{gap:13px}.brand-symbol{width:46px;height:46px;color:#d85631;flex:none}.brand-copy{display:flex;flex-direction:column;gap:2px;line-height:1.1}.brand-copy strong{font-family:"Songti SC",Georgia,serif;font-size:24px;letter-spacing:.08em}.brand-copy small{font-size:10px;font-weight:800;letter-spacing:.17em;color:#748783}.nav button.active{background:#173a37}.nav button:hover:not(.active){background:#edf5f2;color:#173a37}
main{padding-top:48px;padding-bottom:80px}.hero-kicker{display:inline-flex;align-items:center;gap:10px;color:#b75b3e;font-size:12px;font-weight:750;letter-spacing:.1em}.hero-kicker:before{content:"";display:block;width:22px;height:2px;background:#d85631}.hero h1{margin-top:20px}.hero-card{background:#fff9f6;border-color:#f4e2d8;box-shadow:0 18px 40px rgba(216,86,49,.09)}.panel,.library-card,.mode-card{box-shadow:none}.panel{border-color:#dde8e3}.mode-card:hover,.mode-card.selected{background:#fff9f5}.mode-icon{background:#fff0e9}.stats{gap:36px}.stat strong{color:#1d514a}.section{margin-top:56px}.section-head{margin-bottom:20px}.section-head p{line-height:1.6}.chapter-details{margin-top:20px;border:1px solid #e5ede9;border-radius:16px;padding:13px 17px;background:#fbfdfc}.chapter-details summary{cursor:pointer;font-size:13px;font-weight:650;color:#38615a}.chapter-details .flow{margin-top:15px}.record-section{display:flex;justify-content:center}.record-panel{width:min(100%,760px);text-align:center;padding:32px 28px;background:#f9fcfb}.record-panel .btn-row{justify-content:center;margin-top:20px}.record-panel h2{margin-bottom:8px}.record-panel p{margin-bottom:0}.footer{display:none}
.personal-intro{max-width:760px}.personal-grid{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:18px}.personal-card{background:#fff;border:1px solid var(--line);border-radius:22px;padding:24px}.personal-card h3{font-size:23px}.personal-card p{line-height:1.7}.upload-box{display:grid;gap:10px;border:1.5px dashed #bdd5cc;border-radius:15px;padding:20px;background:#f8fcfa}.upload-box input{max-width:100%}.upload-box strong{color:#1e5148}.personal-status{border-radius:12px;padding:12px 15px;font-size:13px;line-height:1.6;background:#eef7f3;color:#2a5e50}.personal-status.error{background:#fff1ed;color:#a84c31}.bank-list{display:grid;gap:12px}.bank-row{display:flex;align-items:center;justify-content:space-between;gap:16px;padding:18px 20px;border:1px solid var(--line);border-radius:15px;background:white}.bank-row h3{font-family:inherit;font-size:17px;margin:0 0 5px}.bank-row p{font-size:12px;color:var(--muted);margin:0}.bank-row .btn-row{justify-content:flex-end}.source-preview{max-height:160px;overflow:auto;padding:14px;border-radius:12px;border:1px solid var(--line);background:#f9fcfb;color:#5c6d67;font-size:12px;white-space:pre-wrap;overflow-wrap:anywhere}.personal-progress{height:9px;border-radius:99px;background:#e7eee9;overflow:hidden}.personal-progress span{display:block;height:100%;background:#d85631}.mcq-stem{font-size:clamp(23px,3vw,30px);line-height:1.5;margin:22px 0}.source-quote{font-size:12px;color:#5f756d;border-left:3px solid #a5c6b9;padding:8px 12px;margin-top:14px;background:#f5faf7}.setup-note{font-size:12px;color:#6d7b76;line-height:1.7}
@media(max-width:800px){.personal-grid{grid-template-columns:1fr}.header-inner{align-items:flex-start;flex-direction:column;padding-top:12px;padding-bottom:12px;gap:10px}.nav{width:100%;overflow:auto}.nav button{flex:none}}
@media(max-width:560px){.brand-symbol{width:36px;height:36px}.brand-copy strong{font-size:19px}.brand-copy small{font-size:8px}.nav button{font-size:12px;padding:7px 9px}.personal-card{padding:18px}.bank-row{align-items:flex-start;flex-direction:column}.bank-row .btn-row{justify-content:flex-start}.record-panel{padding:24px 18px}}
.filter-preview{margin:14px 0 0;font-size:13px;color:#657c73;line-height:1.65}.filter-preview strong{color:#20584d}

.answer-actions .btn.selected{border-color:var(--accent);color:var(--accent)}
.other-options{margin-top:14px;padding-top:12px;border-top:1px dashed var(--line)}
.other-options .other-title{margin:0 0 8px;font-weight:650}
.other-options ul{list-style:none;margin:0;padding:0;display:grid;gap:8px}
.other-option{display:flex;align-items:center;gap:12px;background:rgba(255,255,255,.75);border:1px solid var(--line);border-radius:12px;padding:10px 12px}
.other-option .letter{display:grid;place-items:center;flex:0 0 27px;width:27px;height:27px;border-radius:8px;background:#f1f0eb;font-size:12px;font-weight:800;color:var(--muted)}
.other-body{flex:1;min-width:0}
.other-body p{margin:0}
.other-main{line-height:1.5;overflow-wrap:anywhere}
.other-sub{font-size:13px;color:var(--muted, #6b6b6b);margin-top:3px!important;line-height:1.5}
.other-option .molecule.other-mol{flex:none;width:150px;height:96px;margin:0}
.other-option .molecule.other-mol svg{width:100%;height:100%}
@media(max-width:560px){.other-option.has-mol{flex-wrap:wrap}.other-option .molecule.other-mol{width:100%;height:110px}.answer-actions{flex-wrap:wrap}}