*{box-sizing:border-box} :root{font-family:"Segoe UI","Microsoft YaHei",sans-serif;color:#18324f;background:#edf2f8;font-synthesis:none}body{margin:0}button,input,select{font:inherit}button,a,input,select{touch-action:manipulation}button{cursor:pointer;min-height:44px;border:1px solid #cbd7e5;background:white;color:#244b74;padding:10px 17px;border-radius:8px;line-height:1.4}button:hover{background:#eaf1fa;border-color:#829ebd}button:disabled{opacity:.5;cursor:default}button:focus-visible,a:focus-visible,input:focus-visible,select:focus-visible{outline:3px solid #427ec1;outline-offset:3px}a{color:#245c9f}input,select{min-height:46px;padding:10px 12px;background:#fff;border:1px solid #bdccde;border-radius:7px;max-width:100%;color:#18324f}input{width:100%}label{display:block;margin:15px 0;font-size:14px;font-weight:600}label input,label select{display:block;margin-top:7px}h1{font-size:clamp(27px,3vw,38px);font-weight:650;letter-spacing:-.035em;line-height:1.25;margin:0 0 14px}h2{font-size:23px;letter-spacing:-.02em;margin:0 0 14px}h3{font-size:18px;margin:24px 0 10px}p{line-height:1.65;max-width:72ch}small{font-weight:400}.topbar{height:84px;padding:0 5vw;display:flex;align-items:center;justify-content:space-between;gap:20px;background:white;border-bottom:1px solid #d5dfeb}.brand{display:flex;align-items:baseline;gap:14px;font-size:27px;font-weight:750;letter-spacing:-1px;color:#18324f;text-decoration:none}.brand span{font-size:14px;font-weight:400;letter-spacing:0;color:#62748a}.account-tools{display:flex;align-items:center;gap:18px;font-size:14px}#language{border:0;background:#edf2f8}#identity{max-width:180px;overflow-wrap:anywhere}main{max-width:1320px;margin:28px auto;padding:0 28px}#welcome{padding:48px 0 12px;text-align:center}#welcome p{margin:12px auto;color:#62748a}#auth{max-width:470px;margin:0 auto 60px;background:white;padding:32px;border-radius:14px;border:1px solid #d5dfeb}#auth p{font-size:13px;color:#62748a}#status{margin:0 0 15px;min-height:25px;font-size:14px;color:#246951}#status:empty{min-height:0;margin:0}#workspace{display:grid;grid-template-columns:190px minmax(0,1fr);gap:30px;align-items:start}#workspace[hidden],[hidden]{display:none!important}#app-navigation{position:sticky;top:24px;display:grid;gap:8px;padding-top:8px}#app-navigation button{border:0;background:transparent;text-align:left;padding:14px 18px;color:#526982}#app-navigation button[aria-current=page]{background:#18324f;color:white}.workspace-body{min-width:0;background:white;border:1px solid #d5dfeb;border-radius:16px;padding:38px;min-height:660px}.intro{color:#62748a;margin-bottom:32px}.practice-grid{display:grid;grid-template-columns:1fr 1.15fr;gap:28px;align-items:start}.paper-practice{padding-right:24px;border-right:1px solid #dbe4ee}.paper-practice p{color:#62748a;font-size:14px}.paper-practice nav{display:grid;gap:12px}.paper-practice select{width:100%}.paper-practice button{width:100%;text-align:left}.paper-practice #new,#random-start,#login button[type=submit],#finish,#teacher-form button{background:#245c9f;color:white;border-color:#245c9f}fieldset{border:0;padding:0;margin:0;min-width:0}legend{font-size:23px;font-weight:650;margin-bottom:8px}fieldset p{font-size:13px;color:#62748a}fieldset select{width:100%}#random-count{max-width:140px}#random-start{width:100%;margin-top:10px}.workspace-footer{border-top:1px solid #e1e8f1;margin-top:36px;padding-top:18px;display:flex;align-items:center;justify-content:space-between;gap:15px;font-size:12px;color:#62748a}.workspace-footer button{font-size:13px;border:0}#sessions{display:grid;gap:10px}#sessions button{padding:18px;text-align:left;background:#f4f7fb}#statistics>p{color:#62748a;font-size:14px}#statistics h3{padding-top:20px;border-top:1px solid #dbe4ee}#teacher-form{background:#f4f7fb;padding:24px;border-radius:10px;margin-bottom:28px}#teacher-form p{font-size:14px;color:#62748a}#assignment-list button{margin:5px}#assignment-report{line-height:1.7}#question{max-width:760px;margin:auto}#counter{font-size:14px;color:#62748a;margin-top:30px}#back-to-practice{border:0;background:#edf2f8}#stem{font-family:Georgia,"Times New Roman",serif;font-size:20px;white-space:pre-wrap;line-height:1.85;margin:30px 0}img{max-width:100%;height:auto}#options{display:grid;gap:10px;margin-bottom:28px}#options button{width:100%;text-align:left;padding:16px 20px;min-height:58px;background:#f7f9fc;color:#18324f}#options button[aria-pressed=true]{border:2px solid #245c9f;background:#eaf2fd;padding:15px 19px}#question>nav{display:flex;flex-wrap:wrap;gap:8px;border-top:1px solid #dbe4ee;padding-top:22px}#result{font-weight:600;padding-top:12px}#review{margin-top:32px;border-top:1px solid #dbe4ee;padding-top:25px}#review button{display:block;width:100%;text-align:left;margin:8px 0;overflow-wrap:anywhere}#review p{white-space:pre-wrap;font-size:16px;line-height:1.85}.katex-display{overflow-x:auto;overflow-y:hidden}.katex{font-size:1.08em}#favorite{font-size:13px}button,select{max-width:100%}
@media(max-width:1000px){#workspace{grid-template-columns:155px minmax(0,1fr);gap:18px}.workspace-body{padding:26px}.practice-grid{grid-template-columns:1fr}.paper-practice{padding:0 0 24px;border-right:0;border-bottom:1px solid #dbe4ee}.paper-practice nav{grid-template-columns:1fr 1fr}.paper-practice select{grid-column:1/-1}}
@media(max-width:650px){.topbar{height:auto;min-height:76px;padding:14px 16px}.brand{font-size:24px}.brand span{display:none}.account-tools{gap:8px}#identity{max-width:100px;font-size:12px}main{padding:0 12px;margin:16px auto}#workspace{display:block}#app-navigation{position:static;display:grid;grid-template-columns:1fr 1fr;gap:5px;margin-bottom:14px;padding:0}#app-navigation button{text-align:center;padding:10px 6px}.workspace-body{padding:22px 16px;min-height:0;border-radius:12px}.paper-practice nav{grid-template-columns:1fr}.paper-practice select{grid-column:auto}.workspace-footer{align-items:flex-start}#stem{font-size:18px}#question>nav button{flex:1 1 42%;padding:10px 8px}#teacher-form{padding:15px}#auth{padding:24px}#review button{font-size:14px}.intro{margin-bottom:24px}}

/* Keep long content within the working area without shrinking touch controls. */
button,select,summary{overflow-wrap:anywhere}
button{white-space:normal}
.submission-actions{display:flex;justify-content:flex-end;margin-top:28px;padding-top:24px;border-top:1px solid #d5dfeb}
.submission-actions #finish{border-color:#b77970;color:#8a3026;background:#fff8f6;min-width:120px}
.submission-actions #finish:hover{background:#fbe9e5}
input,select{min-width:0}
input[type=checkbox]{display:inline-block;width:20px;min-height:20px;margin:0 10px 0 0;vertical-align:middle;accent-color:#245c9f}
summary{cursor:pointer;min-height:44px;padding:11px 0;line-height:1.5}
summary:focus-visible,[tabindex]:focus-visible{outline:3px solid #427ec1;outline-offset:3px}
.skip-link{position:absolute;top:8px;left:12px;padding:12px 16px;background:white;border:2px solid #245c9f;border-radius:8px;transform:translateY(-160%);z-index:10}
.skip-link:focus{transform:translateY(0)}
.topbar,.account-tools,.workspace-footer{flex-wrap:wrap}
.account-tools{min-width:0}
.account-settings{margin-top:30px;border-top:1px solid #dbe4ee;padding-top:12px}
.account-settings form{max-width:430px;padding-bottom:10px}
.account-settings p{font-size:14px;color:#62748a}
#login{display:flex;flex-wrap:wrap;gap:10px}
#login label{flex:1 1 100%;margin:8px 0}
#auth>a{display:inline-flex;align-items:center;min-height:44px;line-height:1.5}
#status,#result,#counter,#assignment-report,#statistics,#practice-next-actions{overflow-wrap:anywhere}
#stem,#options button,#review .question-detail{min-width:0;max-width:100%;overflow-x:auto;overscroll-behavior-x:contain}
#options button{overflow-wrap:anywhere}
.katex-display{max-width:100%;padding:4px 0}
.katex-display>.katex{white-space:nowrap}
#practice-next-actions:empty{display:none}
#practice-next-actions{margin-bottom:28px;padding:20px;border-left:3px solid #245c9f;background:#f4f7fb;border-radius:0 8px 8px 0}
#practice-next-actions h2{font-size:19px}
#practice-next-actions h3{margin-top:15px}
#practice-next-actions button{margin:4px 6px 4px 0}
#practice-next-actions p:last-child{margin-bottom:0}
#history-controls{display:flex;align-items:center;flex-wrap:wrap;gap:10px;margin-bottom:18px}
#history-controls label{margin:0;flex:1 1 180px}
#history-controls select{width:100%}
#history-page{font-size:14px;color:#62748a}
#sessions button{display:grid;gap:7px;width:100%;overflow-wrap:anywhere}
#sessions button span{font-size:14px;color:#526982}
#sessions button time{font-variant-numeric:tabular-nums}
#local-recovery{margin-top:22px;border-top:1px solid #dbe4ee;padding-top:10px;overflow-wrap:anywhere}
#local-recovery button{margin:5px 5px 5px 0}
#remaining-time{display:block;position:sticky;top:8px;z-index:5;font-variant-numeric:tabular-nums;max-width:100%;line-height:1.6;font-weight:700;padding:12px;background:#edf2f8;border:1px solid #bdccde;border-radius:6px;box-shadow:0 2px 8px #18334f12}
#remaining-time[hidden]{display:none}
#sync-conflict{margin:24px 0;padding:18px;background:#fff8e9;border:1px solid #d8bd83;border-radius:8px;overflow-wrap:anywhere}
#sync-conflict h2{font-size:20px}
#sync-conflict select{width:100%}
#sync-conflict button{margin:6px 6px 0 0}
#sync-conflict table{display:block;max-width:100%;overflow-x:auto;border-collapse:collapse;margin:16px 0;font-size:14px}
#sync-conflict th,#sync-conflict td{padding:10px;text-align:left;border-bottom:1px solid #d8cdb5;vertical-align:top}
.assignment-preview{padding:20px;margin-top:18px;background:white;border:1px solid #bdccde;border-radius:8px;overflow-wrap:anywhere}
.assignment-preview label{min-height:44px;line-height:1.6}
.assignment-preview details{padding:5px 0}
.assignment-preview p{margin:8px 0}
#assignment-report{margin-top:24px}
#assignment-list p,.report-student-row{padding:15px 0;border-bottom:1px solid #e1e8f1}
.report-student-list,.report-question-list,.review-question-list{display:grid;grid-template-columns:minmax(0,1fr);gap:10px;min-width:0}
.report-question-list>details{min-width:0;max-width:100%}
.assignment-row{padding:10px 0 18px;border-bottom:1px solid #dbe4ee}
.assignment-row h3{margin-top:10px;overflow-wrap:anywhere}
.assignment-row p{font-size:14px;margin:8px 0}
.statistics-sample{padding:10px 0 10px 16px;border-left:3px solid #bdccde;margin:15px 0}
.statistics-sample h4,.statistics-topic h4{margin:0 0 10px;font-size:16px}
.statistics-sample p,.statistics-topic p{margin:6px 0;font-size:14px}
.statistics-topic{padding:18px 0;border-top:1px solid #e1e8f1}
.statistics-topic button{margin-top:8px}
#review>p[data-original]{max-width:100%;overflow-x:auto;overscroll-behavior-x:contain}
.question-detail{padding:12px 16px;background:#f4f7fb;border:1px solid #d5dfeb;border-radius:8px;min-width:0;max-width:100%;overflow-wrap:anywhere}
.question-detail [data-original]{white-space:pre-wrap;max-width:100%;overflow-x:auto}
#report-status-filter,#review-filter{width:100%}
#review .review-question-list button{margin:0}
@media(max-width:650px){
 .topbar{gap:10px}
 #login button{flex:1 1 100%}
 #practice-next-actions{padding:16px}
 #practice-next-actions button,#assignment-list button,.report-student-row button{display:block;width:100%;margin:8px 0}
 .workspace-footer{gap:8px}
 #sync-conflict,.assignment-preview{padding:13px}
 #sync-conflict button{width:100%;margin:6px 0}
 #history-controls>button{flex:1 1 40%}
 #history-page{flex-basis:100%}
 #remaining-time{font-size:14px}
 .question-detail{padding:10px 12px}
}
@media(prefers-reduced-motion:reduce){*{scroll-behavior:auto!important}}
.option-diagram{display:block;max-width:100%;max-height:240px;width:auto;height:auto;margin:8px 0;object-fit:contain}
#options button:disabled{opacity:1}

/* Dedicated bilingual learning-area entrance. */
.area-home{background:#f6f8fb;color:#203653}.area-home main{max-width:1040px;padding:32px;margin:20px auto}.area-brand{font-size:16px;font-weight:650;margin-bottom:60px;color:#586b80}.area-home h1{font-size:clamp(34px,5vw,54px);margin-bottom:28px}.area-home h1 span{display:block;font-family:Georgia,serif;font-size:clamp(20px,3vw,28px);font-weight:400;letter-spacing:0;margin-top:14px}.area-home main>p{color:#586b80;margin:6px 0}.area-home .practice-grid{grid-template-columns:1fr 1fr;gap:26px;margin-top:38px}.area-home .practice-grid section{background:white;border:1px solid #dbe3ed;border-radius:18px;padding:30px;min-width:0}.area-symbol{font-family:Georgia,serif;font-size:76px;height:120px;color:#315e96;line-height:1.2}.area-competitions .area-symbol{color:#21655f}.area-home h2{font-size:30px;margin:10px 0}.area-home h3{font-family:Georgia,serif;font-size:21px;font-weight:400;margin:0 0 24px}.area-home section>p{font-size:15px;color:#586b80}.area-home section>a{display:block;border-top:1px solid #dbe3ed;margin-top:28px;padding:22px 0 4px;text-decoration:none;font-weight:600}.area-home section>a:hover{text-decoration:underline}.assignment-guide{background:#f0f5fa;border-left:3px solid #315e96;padding:16px 20px;margin-bottom:24px}.assignment-guide h2{font-size:18px}.assignment-guide ol{padding-left:22px;line-height:1.8}.assignment-guide small{display:block;color:#586b80}
@media(max-width:640px){.area-home main{padding:22px;margin:0 auto}.area-brand{margin-bottom:36px}.area-home .practice-grid{grid-template-columns:1fr;gap:20px;margin-top:26px}.area-home .practice-grid section{padding:24px}.area-symbol{height:80px;font-size:58px}}