:root{--bg:#faf9f6;--ink:#25272c;--muted:#8b8e95;--border:#e9e7e2;--red:#ed5263;--blue:#e7f2ff}*{box-sizing:border-box}body{margin:0;background:var(--bg);color:var(--ink);font-family:-apple-system,BlinkMacSystemFont,"PingFang SC","Microsoft YaHei",sans-serif;font-size:14px}button,input{font:inherit}button,a{-webkit-tap-highlight-color:transparent}button{cursor:pointer}a{text-decoration:none;color:inherit}button{border:0;background:none;color:inherit}button:focus-visible,a:focus-visible,input:focus-visible{outline:3px solid #86b9e8;outline-offset:3px}.sidebar{width:216px;position:fixed;inset:0 auto 0 0;border-right:1px solid var(--border);padding:30px 18px;display:flex;flex-direction:column;background:var(--bg)}.brand{display:flex;align-items:center;gap:8px;font-weight:750;font-size:21px;letter-spacing:-1px;white-space:nowrap}.brand-mark{display:grid;place-items:center;background:var(--red);color:white;border-radius:9px;width:30px;height:30px;font-size:28px;letter-spacing:0}.beta{font-size:9px;color:#9c9da2;letter-spacing:1px;align-self:flex-end;margin-bottom:4px}.sidebar nav{margin-top:38px;display:grid;gap:9px}.nav-item{display:flex;align-items:center;gap:15px;width:100%;padding:13px 17px;border-radius:10px;text-align:left;color:#666970}.nav-item>span{font-size:21px;line-height:20px}.nav-item.active{background:#efebe5;color:#24262b;font-weight:650}.nav-item:hover{background:#f0eeea}.side-note{margin:48px 16px 0;border-top:1px solid var(--border);padding-top:26px}.little-shapes{font:30px Georgia;color:#a0b2c1;margin-bottom:18px;letter-spacing:9px}.little-shapes span{color:#e4b474}.side-note strong{font-size:15px;line-height:1.8;font-weight:550}.side-note p{color:var(--muted);font-size:12px;line-height:1.8}.side-account{margin-top:auto;display:flex;gap:10px;align-items:center;text-align:left;padding:14px 0;border-top:1px solid var(--border);font-size:12px}.avatar{border-radius:50%;background:#ece8e0;color:#a0927c;width:31px;height:31px;display:grid;place-items:center}.side-account small{display:block;color:var(--muted);font-size:10px;margin-top:5px}.side-account>span:last-child{margin-left:auto}.shell{margin-left:216px}header{height:76px;padding:0 6%;display:flex;align-items:center;justify-content:space-between}.breadcrumb{font-size:12px;color:#96989b}.breadcrumb span{padding:0 12px;color:#cececd}.header-actions{display:flex;gap:18px;align-items:center}.draft-label{font-size:11px;color:#9a9b9b}.login{border:1px solid #dcdad5;border-radius:9px;padding:9px 16px;background:#fff}.mobile-brand{display:none}main{max-width:1260px;margin:auto;padding:25px 6% 0}.intro{display:flex;justify-content:space-between;align-items:center;gap:22px}.eyebrow{font-size:10px;letter-spacing:2.4px;color:#9a9d9c;margin-bottom:14px}h1{font-family:"Songti SC","STSong",Georgia,serif;font-size:38px;font-weight:650;letter-spacing:1px;margin:0}h1 span{color:#72878a}.intro p{font-size:14px;color:#909298;margin:16px 0 0}.upload{display:flex;align-items:center;gap:14px;white-space:nowrap;padding:14px 18px;background:linear-gradient(110deg,#edf7ff,#dceafa);border:1px solid #dbe8f5;border-radius:12px;font-size:13px}.upload>span:first-child{font-size:20px}.upload>span:last-child{margin-left:8px}.search{margin-top:29px;display:flex;align-items:center;gap:12px;padding:9px 10px 9px 19px;background:#fff;border:1px solid #e1dfda;border-radius:13px;box-shadow:0 3px 9px #45403603}.search>span{font-size:28px;color:#a4a7ae;line-height:1}.search input{border:0;outline:0;min-width:0;flex:1;font-size:13px;background:transparent;padding:9px 0}.search input::placeholder{color:#a6a8ae}.search kbd{color:#bdc0c4;font-size:16px}.search button{background:#282b31;color:white;padding:11px 23px;border-radius:9px;font-size:12px}.filters{margin-top:22px}.filter-row{display:flex;align-items:center;gap:15px}.filter-label{font-size:12px;color:#93969c;white-space:nowrap}.choices{display:flex;gap:6px}.choices button{padding:8px 13px;border-radius:7px;font-size:12px;color:#777b82}.choices button.chosen{background:#ece9e3;color:#292c30;font-weight:600}.textbook{margin-left:auto;font-size:12px;color:#8b8d94;white-space:nowrap}.textbook span{padding-left:12px}.subject-tabs{display:flex;gap:26px;border-bottom:1px solid var(--border);margin-top:27px;overflow:auto}.subject-tabs button{padding:11px 0 15px;white-space:nowrap;color:#91939a;font-size:14px;border-bottom:2px solid transparent}.subject-tabs button.selected{color:#292b2f;border-color:#292b2f;font-weight:650}.topic-chips{display:flex;gap:9px;margin:17px 0 30px;overflow:auto;padding-bottom:3px}.topic-chips button{border:1px solid var(--border);border-radius:20px;padding:7px 14px;white-space:nowrap;color:#8b8d92;font-size:11px;background:#fff8}.topic-chips .chosen{background:#eeece7;color:#54575b;border-color:#eeece7}.collection-heading{display:flex;align-items:center;gap:13px;margin:0 0 21px}.section-icon{width:48px;height:48px;display:grid;place-items:center;border-radius:12px;background:#eaf0e8;color:#92a889;font:36px Georgia}.collection-heading h2{font-size:19px;margin:0 0 7px;font-weight:650}.collection-heading p{font-size:12px;color:#9699a0;margin:0}.result-count{font-size:11px;color:#989ba1;margin-left:auto;white-space:nowrap}.cards{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:22px}.card{background:white;border:1px solid #e9e7e3;border-radius:16px;padding:7px;text-align:left;box-shadow:0 3px 6px #3b302b04;display:block;transition:transform .2s,box-shadow .2s}.card:hover{transform:translateY(-4px);box-shadow:0 9px 22px #3b302b0b}.cover{height:166px;border-radius:10px;position:relative;overflow:hidden;display:grid;place-items:center}.cover svg{width:100%;height:100%;max-width:310px}.cover .pill{position:absolute;left:10px;top:10px;border:1px solid #ffffffb0;background:#ffffffb0;backdrop-filter:blur(5px);padding:4px 8px;border-radius:6px;font-size:9px;color:#657c83}.play{position:absolute;bottom:10px;right:10px;width:28px;height:28px;border-radius:50%;display:grid;place-items:center;color:#536974;background:#ffffffba;font-size:10px;transition:scale .2s}.card:hover .play{scale:1.12}.card-body{padding:14px 11px 10px}.card-meta{font-size:10px;letter-spacing:.2px;color:#969aa0;display:flex;justify-content:space-between;gap:5px}.card-meta .real{color:#547b6a}.card h3{font-size:15px;line-height:1.55;margin:8px 0 6px;font-weight:650}.card p{font-size:11px;line-height:1.7;color:#92969d;margin:0;min-height:36px}.card-bottom{display:flex;align-items:center;gap:7px;border-top:1px solid #f3f2ef;margin-top:14px;padding-top:10px;color:#a0a3a8;font-size:10px}.card-bottom span:first-child{padding:3px 6px;border-radius:4px;background:#f6f5f2;color:#8b8d91}.card-bottom span:last-child{margin-left:auto;color:#82968e}.upload-strip{border:1px solid var(--border);border-radius:14px;padding:23px 25px;display:flex;justify-content:space-between;align-items:center;gap:18px;margin:35px 0;background:#f3f2ed}.upload-strip h3{font-size:14px;margin:0 0 7px}.upload-strip p{font-size:12px;color:#9a9b9f;margin:0}.strip-icon{float:left;font-size:32px;margin:2px 18px 0 0;color:#8d9da3}.upload-strip button{font-size:12px;white-space:nowrap}.upload-strip button:hover{text-decoration:underline}footer{display:flex;justify-content:space-between;padding:0 0 27px;font-size:10px;color:#b0b1b4;gap:15px}dialog{border:1px solid var(--border);border-radius:20px;max-width:480px;width:calc(100% - 36px);padding:32px;background:var(--bg);box-shadow:0 20px 100px #20242b22}dialog::backdrop{background:#25272c55;backdrop-filter:blur(3px)}.close{position:absolute;right:12px;top:9px;font-size:25px;color:#989b9f}dialog h2{font-size:23px;margin:10px 0 15px}dialog p{line-height:1.9;color:#81858d;font-size:13px}.dialog-label{font-size:11px;letter-spacing:1px;color:#91a19e}.dialog-primary{display:block;padding:13px 20px;background:#292c31;color:white;border-radius:9px;text-align:center;margin-top:24px;font-size:13px}.dialog-note{border:1px dashed #d8d5cd;padding:15px;border-radius:10px;color:#93969d;font-size:12px;line-height:1.9}.dialog-input{padding:13px;border:1px solid #dedcd7;border-radius:9px;width:100%;margin-bottom:10px;background:#fff;color:#989b9f}.small{font-size:11px!important}#empty{text-align:center;padding:65px 15px;color:#9a9da2}#empty>span{font-size:40px}#empty h3{color:#666b72;font-size:16px}#empty p{font-size:13px}#empty button{border:1px solid var(--border);border-radius:8px;padding:10px 20px;margin-top:14px}button:hover{filter:brightness(.98)}@media(min-width:1500px){.cover{height:190px}}@media(max-width:1100px){.sidebar{width:185px;padding:26px 14px}.brand{font-size:19px}.brand .beta{display:none}.shell{margin-left:185px}main{padding:20px 5% 0}header{padding:0 5%}.cards{grid-template-columns:repeat(2,minmax(0,1fr));gap:18px}.upload{padding:12px;font-size:11px;gap:7px}h1{font-size:33px}.intro p{font-size:12px}.cover{height:180px}.draft-label{display:none}}@media(max-width:700px){.sidebar{display:none}.shell{margin-left:0}header{height:64px;padding:0 20px;border-bottom:1px solid var(--border)}.breadcrumb{display:none}.mobile-brand{display:block;font-size:18px;font-weight:700;color:#32353b}.mobile-brand::first-letter{color:var(--red)}.login{font-size:11px;padding:7px 11px}main{padding:28px 20px 0}.intro{display:block;position:relative}.eyebrow{font-size:9px;margin-bottom:12px}h1{font-size:32px}.intro p{font-size:12px;line-height:1.8;margin:12px 0 0}.upload{margin-top:19px;width:100%;justify-content:center;font-size:12px}.upload span:last-child{margin-left:auto}.upload span:first-child{margin-right:auto}.search{margin-top:15px;padding:6px 7px 6px 13px;gap:8px}.search input{font-size:11px}.search kbd{display:none}.search button{padding:10px 13px;font-size:11px}.filter-row{gap:5px;flex-wrap:wrap}.filter-label{font-size:10px;margin-right:5px}.choices{gap:1px;flex:1}.choices button{font-size:11px;padding:8px 9px}.textbook{padding-top:11px;font-size:10px}.subject-tabs{gap:25px;margin-top:14px}.subject-tabs button{font-size:12px}.topic-chips{margin-bottom:25px;gap:7px}.topic-chips button{font-size:10px;padding:6px 11px}.collection-heading{gap:10px;margin-bottom:16px}.collection-heading h2{font-size:16px}.collection-heading p{font-size:10px;line-height:1.5}.section-icon{width:38px;height:38px;font-size:30px;flex-shrink:0}.result-count{font-size:9px}.cards{gap:12px}.cover{height:118px}.card{border-radius:12px;padding:5px}.cover{border-radius:8px}.cover .pill{font-size:8px;padding:3px 5px;left:6px;top:6px}.card-body{padding:10px 7px 7px}.card-meta{font-size:8px;flex-wrap:wrap;gap:4px}.card h3{font-size:12px;margin:6px 0;line-height:1.6}.card p{font-size:10px;min-height:48px}.card-bottom{font-size:8px;gap:2px;margin-top:9px;padding-top:8px}.card-bottom span:first-child{padding:2px 3px}.play{width:23px;height:23px;font-size:8px;right:6px;bottom:6px}.upload-strip{padding:19px 16px;display:block;margin:25px 0}.strip-icon{display:none}.upload-strip h3{font-size:13px}.upload-strip p{font-size:11px;line-height:1.8}.upload-strip button{padding:15px 0 0;font-size:11px}footer{display:block;font-size:9px;line-height:2}footer span{display:block}}@media(max-width:350px){.cards{grid-template-columns:1fr}.cover{height:170px}.card p{min-height:0}.choices button{padding:8px 6px}}@media(prefers-reduced-motion:reduce){*{transition:none!important}}
/* Keep the grade chooser readable on small screens instead of squeezing labels. */
body .choices button{white-space:nowrap}
@media(max-width:700px){body .choices{flex:none}body .textbook{width:100%;text-align:right;padding-top:9px}body .card h3{font-size:13px}body .card p{font-size:11px}}
.cover img{width:100%;height:100%;object-fit:contain;background:#1c222b}.problem-preview{padding:42px 22px 18px;font-size:15px;line-height:1.8;color:#3b4e5b;overflow:hidden;display:-webkit-box;-webkit-line-clamp:5;-webkit-box-orient:vertical}.full-problem{white-space:pre-wrap;line-height:1.9}#topics{flex-wrap:wrap;max-height:146px;overflow:auto}#loadMore{display:block;margin:26px auto}#loadMore[hidden]{display:none}
.card-problem{height:4.5em;overflow:hidden;line-height:1.5;overflow-wrap:anywhere}.full-problem{overflow-wrap:anywhere}.cover .pill{z-index:1}
.brand-lockup{display:block;width:fit-content;color:#213e43}.brand-lockup .brand{gap:10px;letter-spacing:0;font-weight:400}.brand-symbol{width:40px;height:40px;flex:none}.brand-type{display:flex;flex-direction:column;gap:4px}.brand-type strong{font-size:20px;line-height:1.15;font-weight:750;letter-spacing:1px}.brand-type>span{font-size:9px;letter-spacing:1.8px;color:#7b8e8c}.brand-slogan{display:block;margin-top:12px;font-size:11px;font-weight:400;color:#89918f;letter-spacing:1px}.mobile-brand{display:none}.sr-only{position:absolute;width:1px;height:1px;padding:0;margin:-1px;overflow:hidden;clip:rect(0,0,0,0);white-space:nowrap;border:0}.discovery-bar{display:flex;align-items:center;gap:12px}.discovery-bar .search{flex:1;margin-top:0;min-width:0}.discovery-bar .upload{margin:0;min-height:55px;flex:none}.shell main{padding-top:14px}
@media(max-width:1100px){.brand-symbol{width:36px;height:36px}.brand-type strong{font-size:18px}.brand-type>span{font-size:8px;letter-spacing:1.5px}.brand-slogan{font-size:10px;letter-spacing:.8px}.discovery-bar .upload{gap:8px;padding:12px}}
@media(max-width:700px){.mobile-brand{display:block}header{height:98px;padding:12px 20px}.mobile-brand .brand-symbol{width:32px;height:32px}.mobile-brand .brand{gap:8px}.mobile-brand .brand-type strong{font-size:17px}.mobile-brand .brand-type>span{font-size:8px;letter-spacing:1.3px}.mobile-brand .brand-slogan{font-size:10px;margin-top:8px;letter-spacing:.8px}.header-actions{gap:0}.login{font-size:10px;padding:9px}.shell main{padding-top:20px}.discovery-bar{gap:8px}.discovery-bar .search{padding:5px 6px 5px 10px;gap:6px}.discovery-bar .search input{font-size:11px}.discovery-bar .search button{padding:10px;font-size:10px}.discovery-bar .search input::placeholder{color:#a6a8ae}.discovery-bar .upload{width:auto;min-height:47px;padding:10px;font-size:11px;gap:6px}.discovery-bar .upload>span:last-child{display:none}.discovery-bar .upload>span:first-child{font-size:17px;margin:0}}
@media(max-width:350px){header{padding-right:14px;padding-left:14px}.mobile-brand .brand-type strong{font-size:15px}.mobile-brand .brand-symbol{width:28px;height:28px}.login{font-size:9px;padding:8px}.discovery-bar{flex-wrap:wrap}.discovery-bar .search{flex-basis:100%}.discovery-bar .upload{width:100%}}
.brand-symbol{border-radius:9px;object-fit:contain}.sidebar{overflow-y:auto}
.header-actions{margin-left:auto}@media(min-width:701px){.shell>header{height:64px}}
.sidebar .nav-item{display:grid;grid-template-columns:22px minmax(0,1fr);column-gap:14px;align-items:center;min-height:48px;padding:13px 17px;font-size:14px;line-height:22px}.nav-icon{display:block;width:22px;height:22px;fill:none;stroke:currentColor;stroke-width:1.8;stroke-linecap:round;stroke-linejoin:round}.nav-item>.nav-label{display:block;font-size:14px;line-height:22px;white-space:nowrap;letter-spacing:0}.brand-slogan{letter-spacing:0;white-space:nowrap}@media(max-width:700px){.mobile-brand .brand-slogan{letter-spacing:0}}
.brand-lockup{display:inline-grid;grid-template-columns:max-content}.brand-slogan{width:100%;max-width:0;min-width:100%;text-align:justify;text-align-last:justify}.mobile-brand{display:none}@media(max-width:700px){.mobile-brand{display:inline-grid}}
.login{background:#18191b;color:#fff;border-color:#18191b}
.discovery-bar .search .search-submit{display:grid;place-items:center;flex:0 0 44px;width:44px;height:44px;padding:0;border-radius:50%;background:#fff;color:#8b909b;border:1px solid #eceef3;box-shadow:0 1px 4px #292f4410}.search-submit svg{width:25px;height:25px;fill:none;stroke:currentColor;stroke-width:2.2;stroke-linecap:round;stroke-linejoin:round}.discovery-bar .search .search-submit:hover{background:#f3f4f8;color:#525865}.discovery-bar .search .search-submit:active{background:#eaeef5}
.mobile-collections{display:none}#myCourseTabs:not([hidden]){display:flex;gap:8px;margin:8px 0 18px;flex-wrap:wrap}#myCourseTabs[hidden]{display:none}#myCourseTabs button{border:1px solid #e4e1dd;background:#fff;border-radius:18px;padding:8px 16px;color:#4f5759;font:inherit;font-size:13px}#myCourseTabs button[aria-pressed=true]{background:#282b2e;color:#fff;border-color:#282b2e}.dialog-primary+.dialog-primary{margin-left:10px}.dialog-primary:disabled{opacity:.5;cursor:not-allowed}#collectionNotice{color:#7a8183;margin:0 0 18px;font-size:12px;line-height:1.6}
.task-cover{display:flex;flex-direction:column;align-items:center;justify-content:center;gap:12px;background:#f1efeb;color:#7a8183;font-size:13px}.task-symbol{display:grid;place-items:center;width:46px;height:46px;border:1px solid #d6d3cf;border-radius:50%;font-size:28px;color:#565f62}
@media(max-width:700px){.mobile-collections{display:flex;gap:8px;margin:8px 0 16px}.mobile-collections button{border:1px solid #e4e1dd;background:#fff;border-radius:18px;padding:7px 13px;color:#4f5759;font:inherit;font-size:12px}}
.creation-unread{display:inline-block;margin-bottom:9px;padding:4px 8px;border-radius:6px;background:#fff0f2;color:#cc304a;font-size:11px}#markCreationSeen{margin:0 0 18px;padding:8px 14px;border:1px solid var(--border);border-radius:16px;background:#fff;color:var(--ink);font-size:12px}#markCreationSeen:disabled{opacity:.5;cursor:wait}