:root{font-family:Inter,"Segoe UI",Arial,sans-serif;font-synthesis:none;color:var(--ink);--blue:#235ee7;--ink:#172534;--muted:#637489;--line:#dce3ee;--paper:#fff;--bg:#f3f5f9;--pale:#edf3ff;--success:#19794c;--success-bg:#ecf8f1;--danger:#b93d46;--danger-bg:#fff0f1;--warning:#896016;--warning-bg:#fff7e8;--code-bg:#f5f7fb;--button-ink:#fff;color-scheme:light}
*{box-sizing:border-box}body{margin:0;background:var(--bg)}button,input,select,textarea{font:inherit}button,input,select,textarea,a{-webkit-tap-highlight-color:transparent}button{cursor:pointer;color:inherit;border:0;background:none}button:disabled{cursor:default;opacity:.4}button:focus-visible,a:focus-visible,input:focus-visible,select:focus-visible,textarea:focus-visible,summary:focus-visible{outline:3px solid var(--blue);outline-offset:3px}a{color:var(--blue);text-decoration:none}a:hover{text-decoration:underline}[hidden]{display:none!important}
.topbar{height:62px;background:var(--paper);display:flex;align-items:center;justify-content:space-between;padding:0 28px;border-bottom:1px solid var(--line);position:sticky;top:0;z-index:5}.brand{display:flex;align-items:center;gap:9px;font-size:21px;font-weight:750;letter-spacing:-.7px;color:var(--ink)}.brand:hover{text-decoration:none}.brand span{font-size:9px;color:var(--muted);letter-spacing:1.5px;margin-left:14px;border-left:1px solid var(--line);padding-left:20px;font-weight:650}.header-actions{display:flex;align-items:center;gap:6px}.quiet{font-size:13px;color:var(--muted);padding:11px 12px;border-radius:6px;min-height:42px}.quiet:hover{background:var(--pale);color:var(--blue)}
.layout{display:grid;grid-template-columns:270px minmax(0,1fr);min-height:calc(100vh - 62px)}.sidebar{background:var(--paper);border-right:1px solid var(--line);padding:23px 19px 20px;position:sticky;top:62px;height:calc(100vh - 62px);overflow:auto;display:flex;flex-direction:column}.side-label,.nav-title{font-size:10px;letter-spacing:1.2px;font-weight:700;color:var(--muted);display:flex;justify-content:space-between;align-items:center}.side-label{margin-bottom:9px}select{display:block;width:100%;background:var(--bg);border:1px solid var(--line);border-radius:7px;color:var(--ink);padding:11px 28px 11px 10px;font-size:13px;min-height:44px}.paper-summary{font-size:11px;line-height:1.6;color:var(--muted);margin:8px 1px 19px}.search{border:1px solid var(--line);border-radius:6px;display:flex;align-items:center;gap:8px;padding:11px 10px;color:var(--muted)}.search svg{width:16px;fill:none;stroke:currentColor;stroke-width:1.7;flex-shrink:0}.search input{width:100%;min-width:0;font-size:13px;background:none;border:0;outline:none;color:var(--ink)}kbd{font-size:10px;padding:0 4px;border:1px solid var(--line);border-radius:3px}.filter-tabs{display:flex;gap:3px;background:var(--bg);border-radius:6px;padding:4px;margin:12px 0 24px}.filter-tabs button{font-size:11px;padding:8px 5px;min-height:34px;flex:1;border-radius:4px;color:var(--muted);white-space:nowrap}.filter-tabs button.active{background:var(--paper);color:var(--blue);box-shadow:0 1px 4px #14243512}.nav-title{margin-bottom:15px}.nav-section{font-size:11px;color:var(--muted);margin:19px 1px 10px}.nav-section:first-child{margin-top:0}.question-grid{display:grid;grid-template-columns:repeat(5,1fr);gap:7px}.question-number{height:39px;border:1px solid var(--line);border-radius:6px;font-size:12px;color:var(--muted);position:relative}.question-number:hover{border-color:var(--blue);background:var(--pale)}.question-number.active{background:var(--blue);border-color:var(--blue);color:var(--button-ink)}.question-number.reviewed:not(.active){border-color:var(--success);background:var(--success-bg);color:var(--success)}.question-number.source-gap:after{content:"";position:absolute;right:4px;bottom:4px;width:4px;height:4px;border-radius:50%;background:#d6a04d}.question-number.saved:before{content:"";position:absolute;right:4px;top:3px;width:4px;height:6px;background:var(--blue);clip-path:polygon(0 0,100% 0,100% 100%,50% 70%,0 100%)}.question-number.active:before{background:var(--button-ink)}.legend{display:flex;gap:16px;font-size:10px;color:var(--muted);margin:19px 1px}.legend span{display:flex;align-items:center;gap:5px}.legend i{display:inline-block;width:5px;height:5px;border-radius:50%}.reviewed-dot{background:var(--success)}.gap-dot{background:#d6a04d}.side-bottom{margin-top:auto;padding-top:26px;font-size:11px;color:var(--muted)}.progress{height:4px;background:var(--line);border-radius:3px;margin:10px 0 11px}.progress i{height:100%;background:var(--blue);display:block;border-radius:3px;transition:width .2s}.side-bottom small{font-size:10px;line-height:1.5}.empty-nav{font-size:13px;color:var(--muted);line-height:1.7;padding:15px 0}
main{padding:28px 36px 0;max-width:1280px;width:100%;margin:0 auto}.paper-heading{display:flex;justify-content:space-between;align-items:center;gap:20px}.eyebrow{font-size:10px;letter-spacing:1.15px;font-weight:650;color:var(--muted)}h1{font-size:25px;letter-spacing:-.55px;font-weight:650;margin:9px 0 0;line-height:1.25}.paper-count{font-size:12px;color:var(--muted);white-space:nowrap}.question-toolbar{display:flex;align-items:center;justify-content:space-between;gap:12px;margin:23px 0 12px;font-size:12px;color:var(--muted)}.question-toolbar>div{display:flex;align-items:center;gap:7px}.question-toolbar .outline{font-size:12px;padding:10px 12px}.outline[aria-pressed=true]{background:var(--success-bg);color:var(--success);border-color:var(--success)}.question-card{background:var(--paper);border:1px solid var(--line);border-radius:10px;overflow:hidden}.question-heading{padding:24px 29px;display:flex;align-items:flex-start;justify-content:space-between;gap:20px;border-bottom:1px solid var(--line)}h2{font-size:22px;line-height:1.4;font-weight:650;letter-spacing:-.3px;margin:8px 0 0}.kind{white-space:nowrap;font-size:11px;background:var(--bg);border:1px solid var(--line);padding:7px 10px;border-radius:5px;color:var(--muted)}.source-notice{padding:15px 29px;font-size:13px;color:var(--warning);background:var(--warning-bg);border-bottom:1px solid var(--line);line-height:1.7}.question-body{padding:26px 29px 29px}.question-content{font-size:18px;line-height:1.8;overflow-wrap:anywhere;user-select:text}.question-content p{margin:0 0 20px;white-space:pre-wrap}.question-content p:last-child{margin-bottom:0}.question-content h3{font-size:16px;line-height:1.5;margin:25px 0 10px}.question-content h3:first-child{margin-top:0}.question-content pre{font-family:Consolas,"Cascadia Code",monospace;font-size:16px;line-height:1.7;background:var(--code-bg);border:1px solid var(--line);border-radius:6px;padding:16px 18px;overflow:auto;white-space:pre;overflow-wrap:normal;margin:14px 0 22px}.practice-label{display:block;color:var(--muted);font-size:12px;line-height:1.6;margin-bottom:14px}.answer-area{margin-top:27px;border-top:1px solid var(--line);padding-top:23px}.answer-area fieldset{border:0;padding:0;margin:0;min-width:0}.answer-area legend{font-size:13px;font-weight:600;margin-bottom:14px;color:var(--muted)}.answer-options{display:grid;gap:10px}.answer-option{display:grid;grid-template-columns:26px minmax(0,1fr) 23px;gap:12px;align-items:center;border:1px solid var(--line);border-radius:7px;padding:16px;min-height:60px;cursor:pointer;font-size:17px;line-height:1.65;white-space:pre-wrap;overflow-wrap:anywhere}.answer-option:hover{background:var(--pale);border-color:var(--blue)}.answer-option.selected{border-color:var(--blue);background:var(--pale)}.option-letter{color:var(--muted);font-size:12px;font-weight:600;border:1px solid var(--line);width:26px;height:26px;display:grid;place-items:center;border-radius:4px}.answer-option input{width:21px;height:21px;accent-color:var(--blue);margin:0;justify-self:end;cursor:pointer}.answer-option.correct-answer{border-color:var(--success);background:var(--success-bg)}.answer-option.wrong-answer{border-color:var(--danger);background:var(--danger-bg)}.option-status{font-size:12px;font-weight:600;color:var(--success);grid-column:2/4;margin-top:-5px}.wrong-answer .option-status{color:var(--danger)}.integer-label{font-size:14px;display:block;margin-bottom:10px;font-weight:600}.integer-input{display:block;width:250px;max-width:100%;min-height:48px;padding:10px 13px;border:1px solid var(--line);border-radius:6px;background:var(--bg);color:var(--ink);font-size:18px}.answer-actions{display:flex;gap:12px;align-items:center;margin-top:19px;flex-wrap:wrap}.outline,.primary{font-size:13px;padding:12px 17px;min-height:44px;border-radius:6px;font-weight:550}.outline{background:var(--paper);border:1px solid var(--line);color:var(--muted)}.primary{background:var(--blue);color:var(--button-ink);border:1px solid var(--blue)}.primary:hover{filter:brightness(1.08)}.outline:hover{border-color:var(--blue);color:var(--blue)}.form-error{font-size:13px;color:var(--danger);margin:14px 0 0}.feedback{margin-top:23px;border:1px solid var(--line);border-radius:7px;padding:19px 20px;background:var(--bg);font-size:15px;line-height:1.75}.feedback.correct{border-color:var(--success);background:var(--success-bg)}.feedback.incorrect{border-color:var(--danger)}.feedback-title{display:flex;align-items:center;gap:9px;font-weight:650;font-size:16px}.feedback.correct .feedback-title{color:var(--success)}.feedback.incorrect .feedback-title{color:var(--danger)}.feedback p{margin:10px 0 0;white-space:pre-wrap}.feedback small{font-size:11px;color:var(--muted);display:block;margin-top:15px}.feedback ul{padding-left:22px;margin:12px 0 0}.feedback li{margin:6px 0}.no-grade{margin-top:19px;color:var(--muted);font-size:13px;line-height:1.7}
.mock-ide{margin-top:29px;border:1px solid var(--line);border-radius:8px;overflow:hidden;background:var(--code-bg)}.ide-toolbar{display:flex;justify-content:space-between;align-items:center;gap:12px;flex-wrap:wrap;border-bottom:1px solid var(--line);padding:11px 15px;font-size:12px;color:var(--muted)}.ide-file{display:flex;align-items:center;gap:12px;color:var(--ink);font-family:Consolas,monospace}.language-badge{border:1px solid var(--line);border-radius:4px;padding:4px 8px;font:11px "Segoe UI",sans-serif;color:var(--muted)}.ide-toolbar .quiet{padding:6px 9px;min-height:32px;font-size:12px}.editor-wrap{display:grid;grid-template-columns:44px minmax(0,1fr);height:440px;overflow:hidden}.line-numbers{font:14px/1.7 Consolas,"Cascadia Code",monospace;text-align:right;padding:18px 10px 18px 0;color:var(--muted);background:var(--code-bg);white-space:pre;overflow:hidden;user-select:none}.java-editor{display:block;width:100%;height:100%;min-height:300px;resize:none;border:0;border-radius:0;padding:18px 17px 18px 9px;color:var(--ink);background:var(--code-bg);font:14px/1.7 Consolas,"Cascadia Code",monospace;tab-size:4;white-space:pre;overflow:auto;outline:none}.java-editor:focus-visible{outline-offset:-3px}.ide-status{display:flex;justify-content:space-between;gap:15px;padding:9px 15px;border-top:1px solid var(--line);font-size:11px;color:var(--muted)}.ide-note{font-size:12px;color:var(--muted);line-height:1.6;margin:13px 0 0}.solution-guide{margin-top:18px;border:1px solid var(--line);border-radius:7px;background:var(--bg);padding:18px 20px;font-size:15px;line-height:1.8}.solution-guide h3{font-size:15px;margin:0 0 9px}.solution-guide p{margin:0;white-space:pre-wrap}.source-reference{border-top:1px solid var(--line);font-size:12px;color:var(--muted)}.source-reference summary{cursor:pointer;padding:16px 29px;min-height:47px}.source-reference[open] summary{border-bottom:1px solid var(--line)}#source-captures{padding:18px 29px;display:grid;gap:20px}.source-capture{margin:0;max-width:850px}.source-capture figcaption{display:flex;justify-content:space-between;gap:15px;margin-bottom:12px;font-size:12px}.source-capture img{display:block;width:100%;height:auto;border:1px solid var(--line);background:#fff}
.bottom-navigation{display:flex;justify-content:space-between;align-items:center;margin:20px 0 0;gap:15px}.bottom-navigation>span{font-size:12px;color:var(--muted)}footer{font-size:11px;color:var(--muted);display:flex;justify-content:space-between;border-top:1px solid var(--line);margin-top:30px;padding:20px 0 23px}footer a{color:var(--muted)}dialog{background:var(--paper);border:1px solid var(--line);border-radius:12px;box-shadow:0 20px 100px #0005;color:var(--ink);padding:32px;max-width:580px;width:calc(100% - 30px)}dialog::backdrop{background:#09111bb0;backdrop-filter:blur(3px)}dialog p{font-size:14px;line-height:1.8;color:var(--muted)}dialog h2{font-size:24px;margin-bottom:20px}.dialog-close{position:absolute;right:9px;top:7px;font-size:24px}.shortcuts{font-size:12px;color:var(--muted);line-height:2.4;border-top:1px solid var(--line);padding-top:14px;margin-top:18px}.shortcuts span{display:inline-block;width:55px;color:var(--ink)}.download-link{font-size:12px;display:block;margin-top:16px}#toast{position:fixed;bottom:24px;left:50%;transform:translateX(-50%);background:var(--ink);color:var(--paper);padding:12px 20px;border-radius:6px;font-size:13px;opacity:0;pointer-events:none;transition:opacity .2s;z-index:10}#toast.visible{opacity:1}
@media(min-width:1650px){main{padding:32px 50px 0;max-width:1400px}.question-body{padding:30px 36px}.question-heading{padding:25px 36px}.question-content{font-size:19px}}
@media(max-width:1050px){.layout{grid-template-columns:245px minmax(0,1fr)}.sidebar{padding:20px 15px}main{padding:25px 22px 0}.paper-heading h1{font-size:22px}.paper-count{display:none}.question-heading,.question-body{padding:23px}.question-content{font-size:17px}.question-heading h2{font-size:20px}.kind{font-size:10px}.question-toolbar .quiet{padding:10px 8px}.source-notice{padding:15px 23px}}
@media(max-width:760px){.topbar{height:58px;padding:0 16px}.brand{font-size:20px}.brand span{display:none}.header-actions{gap:0}.topbar .quiet{font-size:12px;padding:9px}.layout{display:block}.sidebar{position:static;height:auto;padding:17px 16px;border-right:0;border-bottom:1px solid var(--line)}.paper-summary{margin:7px 0 13px}.side-label{font-size:9px;margin-bottom:7px}.sidebar select{font-size:13px}.search{padding:10px}.filter-tabs{margin:10px 0 16px}.nav-title{margin-bottom:10px}.nav-section{margin:12px 0 8px}.question-grid{grid-template-columns:repeat(10,minmax(0,1fr));gap:5px}.question-number{height:36px;font-size:11px}.legend{margin:14px 0 0}.side-bottom{padding-top:14px;margin:0}.side-bottom small{display:none}.progress{margin-bottom:0}main{padding:23px 16px 0}.paper-heading h1{font-size:22px}.eyebrow{font-size:9px}.question-toolbar{margin:18px 0 10px;font-size:11px}.question-toolbar .outline{padding:9px 10px;font-size:11px}.question-toolbar .quiet{font-size:12px}.question-heading{padding:20px}.question-heading h2{font-size:20px}.kind{font-size:9px;padding:6px}.question-body{padding:22px 20px}.question-content{font-size:17px;line-height:1.8}.question-content pre{font-size:16px;padding:13px}.source-notice{padding:14px 20px;font-size:12px}.answer-option{font-size:16px;padding:13px 12px;gap:10px;grid-template-columns:23px minmax(0,1fr) 21px}.option-letter{width:23px;height:24px;font-size:11px}.feedback{padding:16px;font-size:14px}.source-reference summary{padding:16px 20px}#source-captures{padding:18px 20px}.bottom-navigation .primary,.bottom-navigation .outline{padding:11px 13px;font-size:12px}.editor-wrap{height:390px;grid-template-columns:35px minmax(0,1fr)}.java-editor,.line-numbers{font-size:13px}.ide-status{font-size:10px}.line-numbers{padding-right:7px}.ide-toolbar{padding:10px}.solution-guide{padding:16px;font-size:14px}footer{font-size:10px}dialog{padding:27px}}
@media(max-width:400px){.question-grid{grid-template-columns:repeat(5,minmax(0,1fr))}.question-toolbar{align-items:flex-start}.question-toolbar>span{padding-top:12px}.question-toolbar>div{gap:0}.question-heading{gap:10px}.question-heading h2{font-size:18px}.kind{white-space:normal;max-width:85px}.ide-status{flex-direction:column;gap:4px}}