:host{color-scheme:light;--ink:#20372e;--muted:#576c60;--paper:#f7f5ef;--green:#24543f;--deep:#143d32;font-family:Inter,"PingFang SC","Microsoft YaHei",sans-serif;-webkit-font-smoothing:antialiased}
*{box-sizing:border-box}:host{scroll-behavior:smooth}.booktree-intro-root{margin:0;color:var(--ink);background:radial-gradient(circle at 15% 18%,#e9f4e5 0,transparent 32%),radial-gradient(circle at 90% 82%,#f9e3d8 0,transparent 29%),#f7f5ef}button,select{font:inherit}button{cursor:pointer}a{color:inherit;text-decoration:none}img{max-width:100%}:focus-visible{outline:3px solid #509e79;outline-offset:3px}.skip-link{position:absolute;left:12px;top:-90px;background:#143d32;color:#fff;padding:10px 14px;z-index:99}.skip-link:focus{top:12px}
.site-header{height:74px;display:flex;align-items:center;gap:22px;padding:0 clamp(18px,4vw,65px);background:#ffffffca;backdrop-filter:blur(18px);border-bottom:1px solid #335f4722}.site-brand{display:flex;align-items:center;gap:10px;min-width:200px}.site-brand img{width:46px;height:46px;object-fit:contain}.site-brand span{display:grid}.site-brand strong{font-size:18px;letter-spacing:.025em}.site-brand small{font-size:8px;letter-spacing:.19em;color:#67806e;font-weight:800}.header-caption{font-size:12px;letter-spacing:.12em;color:#66806e;margin:auto}.header-shelf{background:#21523c;color:#fff;border-radius:999px;padding:11px 16px;font-size:12px;font-weight:800;white-space:nowrap}.header-shelf:hover{background:#173d2f}
.guide-shell{width:min(100% - 40px,1170px);margin:0 auto;padding:25px 0 28px}.book-heading{display:flex;align-items:baseline;justify-content:space-between;gap:12px;padding:0 7px 15px}.book-heading span{font-size:13px;letter-spacing:.08em;font-weight:900;color:#476d56}.book-heading p{font-size:11px;color:#718273;margin:0}.book-stage{display:none;position:relative;width:100%;height:min(690px,calc(100svh - 225px));min-height:490px;perspective:1800px;filter:drop-shadow(0 25px 34px #23402b30)}.is-enhanced .book-stage{display:block}.book-pages-shadow{position:absolute;inset:7px 2px -7px;border-radius:13px;background:#e4e3d8;box-shadow:0 2px 0 #d9d7cb,0 5px 0 #e7e4da}.book-left,.book-right{position:absolute;top:0;bottom:0;width:50%;background:#fff;overflow:hidden;box-shadow:inset 0 0 0 1px #2b67401d}.book-left{left:0;border-radius:13px 2px 2px 13px}.book-right{right:0;border-radius:2px 13px 13px 2px}.book-left:after{content:"";position:absolute;z-index:1;right:0;top:0;bottom:0;width:25px;background:linear-gradient(90deg,transparent,#143d3220);pointer-events:none}.book-right:before{content:"";position:absolute;z-index:1;left:0;top:0;bottom:0;width:24px;background:linear-gradient(90deg,#143d321d,transparent);pointer-events:none}.endpaper{height:100%;padding:48px;display:flex;flex-direction:column;justify-content:space-between;background:repeating-linear-gradient(138deg,#e3eedf 0,#e3eedf 2px,#edf3e8 2px,#edf3e8 12px);color:#6a876d}.endpaper:before{content:"BOOKTREE";font-size:14px;letter-spacing:.5em;font-weight:900}.endpaper:after{content:"每一条记录，都有来处。";font-size:13px;letter-spacing:.17em}
.book-page{height:100%;min-height:0;overflow:auto;overscroll-behavior:contain;scrollbar-color:#aec5af transparent;position:relative}.page-inner{min-height:100%;padding:clamp(26px,3.5vw,52px);display:flex;flex-direction:column;position:relative;z-index:1}.book-page h1,.book-page h2,.book-page p{overflow-wrap:anywhere}.book-page h2{font-size:clamp(30px,3.2vw,45px);line-height:1.22;letter-spacing:-.04em;margin:18px 0 22px}.book-page h2 em{font-style:normal;color:#3f8d65}.book-page p{line-height:1.7}.page-lead{font-size:clamp(13px,1.13vw,16px);color:#385547;margin:0 0 16px}.page-kicker{font-size:10px;letter-spacing:.2em;font-weight:900;color:#4d8061}.page-note{font-size:11px;line-height:1.6;color:#587366;border-top:1px solid #5f886630;padding-top:11px;margin-top:auto}.book-page[data-theme=mint]{background:linear-gradient(150deg,#e6f4e5,#f5faef 60%,#ecf4e6)}.book-page[data-theme=cream]{background:linear-gradient(135deg,#fff8e8,#f5f5df)}.book-page[data-theme=sky]{background:linear-gradient(145deg,#e6f5fa,#f6fcf9)}.book-page[data-theme=lavender]{background:linear-gradient(145deg,#f0ebf9,#fbf8fd)}.book-page[data-theme=peach]{background:linear-gradient(145deg,#fff0e8,#fff9ef)}.book-page[data-theme=gold]{background:linear-gradient(145deg,#fff5d9,#fbf8e8)}.book-page[data-theme=bluegreen]{background:linear-gradient(150deg,#e2f4ef,#f4fbf7)}.book-page[data-theme=sage]{background:linear-gradient(145deg,#e7f0df,#f8fbef)}.book-page[data-theme=coral]{background:linear-gradient(145deg,#fcece5,#fff8ee)}.book-page[data-theme=violet]{background:linear-gradient(145deg,#edeaf7,#f8f6ff)}.book-page[data-theme=rose]{background:linear-gradient(145deg,#f9e8ec,#fff7f5)}
.cover-page{background:#214d3c;color:#f9f8eb}.cover-page .page-inner{padding:clamp(28px,4vw,58px);background:radial-gradient(circle at 50% 36%,#4b886570,transparent 52%),linear-gradient(135deg,#1b4938,#12382e)}.cover-page:before{content:"";position:absolute;inset:16px;border:1px solid #c4d4aa58;border-radius:4px;pointer-events:none;z-index:2}.cover-ribbon,.cover-edition{font-size:10px;letter-spacing:.18em;font-weight:900;color:#cfe3bb}.cover-ribbon{align-self:center}.cover-logo-wrap{align-self:center;background:#f7f5ef;border-radius:50%;width:min(55%,200px);aspect-ratio:1;display:grid;place-items:center;margin:24px 0 18px;box-shadow:0 12px 40px #0c2f2770}.cover-logo-wrap img{width:88%;height:88%;object-fit:contain}.cover-edition{text-align:center}.cover-page h1{font-size:clamp(29px,3vw,42px);line-height:1.38;letter-spacing:-.04em;text-align:center;margin:22px auto 10px}.cover-page h1 span{display:inline-block;color:#ebcb75}.cover-page p{text-align:center;font-size:12px;letter-spacing:.07em;color:#d6e9cd;margin:0}.cover-turn{margin:auto auto 0;padding-top:28px;font-size:12px;font-weight:900;color:#f6ddb3;letter-spacing:.12em}
.intro-page h2 em{color:#33855b}.highlight-quote{font-family:"Songti SC","Noto Serif CJK SC",serif;font-size:clamp(20px,2.2vw,30px);line-height:1.55;color:#1d6747;background:#fffdf2b9;border-left:5px solid #ebbb70;border-radius:8px;padding:17px 20px;margin:12px 0}.page-foot{display:flex;gap:14px;align-items:center;margin-top:auto}.page-foot p{font-size:11px;line-height:1.5;margin:0}.round-number{display:grid;place-items:center;flex:0 0 67px;width:67px;height:67px;border-radius:50%;background:#26704a;color:#fff;font-size:23px;font-weight:900}
.path-map{display:flex;align-items:center;gap:5px;margin:8px 0 25px}.path-node{display:flex;flex-direction:column;align-items:center;justify-content:center;width:23%;aspect-ratio:1;border-radius:50%;background:#f7d28e;color:#604616;font-size:15px;font-weight:900;text-align:center;box-shadow:0 6px 13px #8a622320}.path-node:nth-of-type(3){background:#c6e5c0;color:#27563b}.path-node:nth-of-type(5){background:#efd1b5;color:#71462f}.path-node:nth-of-type(7){background:#cdd8f2;color:#334b7c}.path-node small{font-size:9px;font-weight:700;margin-top:4px}.path-line{flex:1;height:3px;min-width:4px;background:#a5be9a}.feature-pair{display:grid;grid-template-columns:1fr 1fr;gap:11px}.feature-pair div{border-radius:15px;background:#fffef4c7;padding:15px}.feature-pair b{font-size:14px;color:#2a6549}.feature-pair p{font-size:11px;margin:6px 0 0;color:#526a59}
.paper-demo{height:185px;display:flex;justify-content:center;gap:0;margin:4px 0 20px;filter:drop-shadow(0 9px 12px #21607428)}.paper-demo>div{background:#fffef9;border:1px solid #b3cbd0;width:46%;padding:17px;display:flex;flex-direction:column;gap:9px;transform:rotate(-3deg);border-radius:5px}.paper-demo>div+div{transform:rotate(3deg);border-color:#c9d5c8}.paper-demo span{font-size:11px;font-weight:900;color:#50796b}.paper-demo b{font-size:15px}.paper-demo i,.insert-demo i{display:block;width:95%;height:5px;background:#d9e7df;border-radius:3px}.paper-demo i:nth-of-type(2),.insert-demo i:nth-of-type(2){width:75%}.paper-demo i:nth-of-type(3),.insert-demo i:nth-of-type(3){width:88%}.paper-demo small{font-size:9px;color:#779b8a;margin-top:auto}
.dialogue-demo{display:grid;gap:11px;margin:5px 0 25px}.bubble{border-radius:18px;padding:17px 20px;font-size:14px;line-height:1.6;box-shadow:0 6px 16px #6b5d8b13}.bubble-question{background:#ead8f7;color:#51366d;justify-self:end;border-bottom-right-radius:4px;font-weight:900}.bubble-reply{background:#fff;color:#4a6172;justify-self:start;border-bottom-left-radius:4px;max-width:90%}
.sticky-grid{display:grid;grid-template-columns:1fr 1fr;gap:11px;margin:5px 0 20px}.sticky-card{min-height:105px;padding:14px;border-radius:4px;box-shadow:4px 5px 0 #a06b5220;display:flex;flex-direction:column;justify-content:space-between;transform:rotate(-2deg)}.sticky-card:nth-child(2){transform:rotate(2deg)}.sticky-card:nth-child(3){grid-column:1/-1;min-height:82px;transform:rotate(-1deg)}.sticky-green{background:#d9eed8}.sticky-yellow{background:#ffebad}.sticky-pink{background:#f9d9cf}.sticky-card span{font-size:10px;letter-spacing:.08em;font-weight:900;color:#506a58}.sticky-card b{font-size:13px;line-height:1.4}
.insert-demo{display:flex;align-items:center;justify-content:center;height:185px;margin:2px 0 20px;position:relative}.insert-demo>div{width:35%;height:130px;background:#fffefa;border:1px solid #d9d5bc;border-radius:5px;padding:10px;display:flex;flex-direction:column;gap:8px;box-shadow:0 10px 22px #7c673520}.insert-demo .original-paper:first-child{transform:rotate(-11deg) translateX(10px)}.insert-demo .original-paper:last-child{transform:rotate(11deg) translateX(-10px)}.insert-demo .note-paper{background:#f0d9a9;z-index:1;height:155px;width:43%;transform:rotate(-2deg);border-color:#daa865}.insert-demo span{font-size:10px;font-weight:900;color:#5c6655}.insert-demo b{font-size:12px}.insert-demo small{font-size:9px;margin-top:auto;color:#7e653d}
.subject-cards{display:grid;gap:9px;margin:2px 0 15px}.subject-card{display:grid;grid-template-columns:53px 1fr;align-items:start;gap:0 8px;padding:11px 13px;border-radius:11px}.subject-card span{grid-row:1/3;display:grid;place-items:center;width:45px;height:45px;border-radius:50%;font-size:11px;font-weight:900}.subject-card b{font-size:14px}.subject-card p{font-size:10px;margin:3px 0 0}.subject-chinese{background:#fff1d9}.subject-chinese span{background:#eab66b}.subject-english{background:#dcf0e9}.subject-english span{background:#71baa3}.subject-math{background:#e2e8fa}.subject-math span{background:#a2b6e5}
.step-cards{padding:0;margin:4px 0 20px;list-style:none;display:grid;gap:10px}.step-cards li{display:flex;gap:15px;background:#ffffffab;border:1px solid #376f4430;border-radius:12px;padding:12px 15px}.step-cards li>span{font-size:23px;font-weight:900;color:#6b9c66;line-height:1}.step-cards b{font-size:13px}.step-cards p{font-size:11px;margin:3px 0 0;color:#546c5b}.navigation-tip{border-radius:12px;padding:15px 17px;background:#f7d9ca}.navigation-tip b{font-size:13px}.navigation-tip p{font-size:11px;margin:4px 0 0}.family-questions{padding:0;margin:5px 0 24px;list-style:none;display:grid;gap:11px}.family-questions li{background:#fffafaad;border-left:4px solid #9b7bc2;border-radius:8px;padding:13px;font-size:14px;font-weight:900}.family-questions span{font-size:10px;color:#8e65a8;margin-right:10px}
.faq-cards{display:grid;gap:9px;margin:2px 0 18px}.faq-cards>div{background:#fffdfcc7;border-left:3px solid #cf879a;border-radius:9px;padding:10px 13px}.faq-cards b{font-size:12px}.faq-cards p{font-size:10px;color:#6f5b63;margin:3px 0 0;line-height:1.5}.ending-page{background:radial-gradient(circle at 50% 25%,#f3e4b8,transparent 40%),linear-gradient(145deg,#e5f1e3,#fff8e6)}.ending-page .page-inner{align-items:center;text-align:center}.ending-logo{width:min(50%,195px);max-height:150px;object-fit:contain;margin:20px auto 6px}.ending-page h2{font-size:clamp(26px,2.7vw,38px)}.ending-page p{font-size:12px;color:#516b5b;margin:0}.ending-actions{display:flex;gap:9px;justify-content:center;flex-wrap:wrap;margin:25px 0}.ending-actions a{background:#245940;color:white;padding:12px 15px;border-radius:99px;font-size:12px;font-weight:900}.ending-actions a+ a{background:#fff;border:1px solid #add1b0;color:#245940}.ending-page small{font-size:10px;color:#789080;margin-top:auto}
.flip-sheet{position:absolute;z-index:6;top:0;bottom:0;left:50%;width:50%;transform-origin:left center;transform-style:preserve-3d;pointer-events:none}.flip-sheet[hidden]{display:none}.flip-front,.flip-back{position:absolute;inset:0;backface-visibility:hidden;overflow:hidden;background:#fff}.flip-front{border-radius:2px 13px 13px 2px;box-shadow:-6px 4px 18px #18392422}.flip-back{transform:rotateY(180deg);border-radius:13px 2px 2px 13px;box-shadow:6px 4px 18px #18392422}.flip-sheet.is-forward{animation:turn-forward .72s cubic-bezier(.42,.02,.2,1) forwards}.flip-sheet.is-backward{animation:turn-backward .72s cubic-bezier(.35,.02,.2,1) forwards}@keyframes turn-forward{0%{transform:rotateY(0)}50%{box-shadow:0 12px 25px #0c33244d}100%{transform:rotateY(-180deg)}}@keyframes turn-backward{0%{transform:rotateY(-180deg)}50%{box-shadow:0 12px 25px #0c33244d}100%{transform:rotateY(0)}}
.page-hotspot{position:absolute;top:43%;z-index:7;width:35px;height:70px;border:0;background:#1a553321;color:#23553d;font-size:34px;opacity:.35;transition:opacity .2s,background .2s}.page-hotspot:hover{opacity:1;background:#dce9d4}.page-hotspot-prev{left:0;border-radius:0 35px 35px 0}.page-hotspot-next{right:0;border-radius:35px 0 0 35px}.page-hotspot:disabled{display:none}
.book-controls{display:none;align-items:center;gap:18px;justify-content:center;margin:23px auto 13px}.is-enhanced .book-controls{display:flex}.book-controls button{min-width:128px;border:1px solid #96b69b;background:#fffdf5;color:#24553c;border-radius:999px;padding:11px 16px;font-size:13px;font-weight:900}.book-controls button:hover:not(:disabled){background:#e4f2df}.book-controls button:disabled{opacity:.4;cursor:default}.page-position{display:grid;justify-items:center;gap:7px;min-width:190px;color:#587362;font-size:11px;font-weight:800}.page-progress{width:100%;height:4px;border-radius:5px;background:#dbe5d7;overflow:hidden}.page-progress span{display:block;width:0;height:100%;background:linear-gradient(90deg,#439b73,#e7a26d,#997ac0);transition:width .35s}.chapter-picker{display:none;align-items:center;justify-content:center;gap:10px;color:#65806a;font-size:11px}.is-enhanced .chapter-picker{display:flex}.chapter-picker select{border:1px solid #c5d4c5;background:#fffdf7;border-radius:8px;color:#275040;font-size:11px;padding:6px 12px;max-width:190px}.source-pages{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:20px}.source-pages .book-page{min-height:550px;border-radius:10px;box-shadow:0 10px 25px #24432b20}.is-enhanced .source-pages{display:none}
@media(max-width:760px){.site-header{height:61px;padding:0 13px;gap:10px}.site-brand{min-width:0}.site-brand img{width:37px;height:37px}.site-brand strong{font-size:15px}.site-brand small{font-size:6px}.header-caption{display:none}.header-shelf{margin-left:auto;font-size:10px;padding:9px 11px}.guide-shell{width:min(100% - 24px,530px);padding:15px 0}.book-heading{padding:0 2px 10px}.book-heading span{font-size:10px}.book-heading p{font-size:9px}.book-stage{height:calc(100svh - 185px);min-height:420px;max-height:650px}.book-left{display:none}.book-right{left:0;right:0;width:100%;border-radius:11px}.book-right:before{display:none}.flip-sheet{left:0;width:100%}.flip-back,.flip-front{border-radius:11px}.page-inner{padding:25px 27px 28px}.book-page h2{font-size:clamp(28px,8vw,38px);margin:14px 0 18px}.page-lead{font-size:13px}.cover-logo-wrap{width:min(48%,155px);margin:13px 0}.cover-page h1{font-size:clamp(28px,7.4vw,37px);margin:13px 0 8px}.cover-page .page-inner{padding:25px}.book-controls{gap:7px;margin:16px auto 9px}.book-controls button{min-width:88px;padding:10px;font-size:11px}.page-position{min-width:105px;font-size:10px}.chapter-picker{font-size:10px}.source-pages{grid-template-columns:1fr}.source-pages .book-page{min-height:500px}.page-hotspot{top:auto;bottom:0;width:26px;height:42px;font-size:24px;opacity:.5}}
@media(max-width:390px){.book-stage{height:calc(100svh - 173px);min-height:390px}.page-inner{padding:19px 23px 22px}.book-page h2{font-size:27px;margin:10px 0 14px}.page-lead{font-size:12px}.page-note{font-size:10px}.highlight-quote{font-size:19px;padding:12px}.paper-demo,.insert-demo{height:150px}.insert-demo>div{height:105px}.insert-demo .note-paper{height:130px}.subject-card{padding:8px}.subject-card span{width:38px;height:38px}.subject-card p{font-size:9px}.cover-page h1{font-size:27px}.cover-logo-wrap{width:130px}.cover-ribbon,.cover-edition{font-size:9px}}
@media(prefers-reduced-motion:reduce){:host{scroll-behavior:auto}*,*:before,*:after{animation-duration:.01ms!important;transition-duration:.01ms!important}.flip-sheet.is-forward{transform:rotateY(-180deg)}.flip-sheet.is-backward{transform:rotateY(0)}}

/* A quiet paper edge and spine shadow keep the mobile page book-like. */
@media(max-width:760px){
  .book-stage{overflow:hidden;border-radius:11px;background:linear-gradient(90deg,#e0e4d9 0,#f7f4ec 5px,transparent 6px)}
  .book-pages-shadow{left:6px}
  .book-right{left:6px;width:calc(100% - 6px);border-radius:4px 11px 11px 4px;box-shadow:inset 5px 0 8px #243e2e20}
  .flip-sheet{left:6px;width:calc(100% - 6px)}
  .flip-front,.flip-back{border-radius:4px 11px 11px 4px}
  .page-hotspot-prev{left:6px}
}

@media(max-width:760px){
  .booktree-intro-root.is-enhanced{height:100svh;overflow:hidden;display:flex;flex-direction:column}
  .is-enhanced .site-header{flex:0 0 61px}
  .is-enhanced .guide-shell{flex:1;min-height:0;display:flex;flex-direction:column;padding:8px 0}
  .is-enhanced .book-stage{flex:1;min-height:0;max-height:none;height:auto}
  .is-enhanced .book-controls{flex:0 0 auto;margin:8px auto 5px}
  .is-enhanced .chapter-picker{flex:0 0 auto}
}
@media(max-width:390px){
  .cover-page .page-inner{padding:14px 19px}
  .cover-logo-wrap{width:112px;margin:8px 0}
  .cover-page h1{font-size:26px;margin:8px 0 5px}
  .cover-page p{font-size:10px}
  .cover-turn{padding-top:8px}
  .book-controls{gap:5px}
  .book-controls button{min-width:75px;padding:8px 7px}
  .page-position{min-width:117px;font-size:9px}
}

/* Original guide, scoped by the component rather than global UP selectors. */
:host{display:block;font-size:16px;line-height:normal}
.booktree-intro-root{border-radius:16px}
.guide-shell{padding-top:16px}
.book-stage{height:min(690px,calc(100svh - 300px));min-height:460px}
.ending-actions button{font:inherit;background:#fff;border:1px solid #add1b0;color:#245940;padding:12px 15px;border-radius:99px;font-size:12px;font-weight:900}
@media(max-width:760px){.booktree-intro-root.is-enhanced{height:clamp(440px,calc(100svh - 250px),740px);overflow:hidden}.is-enhanced .guide-shell{width:calc(100% - 28px)}.is-enhanced .book-stage{min-height:0}}