:root{--bg:#f6f7f9;--card:#fff;--text:#17191f;--muted:#6f7480;--line:#e7e9ee;--primary:#2758d9;--primary-soft:#eef3ff;--good:#12805c;--good-bg:#eaf8f2;--bad:#c93c3c;--bad-bg:#fff0f0;--warn:#9b6500;--warn-bg:#fff7df;--shadow:0 8px 28px rgba(20,28,45,.07)}
*{box-sizing:border-box;-webkit-tap-highlight-color:transparent}
html,body{margin:0;background:var(--bg);color:var(--text);font-family:-apple-system,BlinkMacSystemFont,"Segoe UI","PingFang SC","Hiragino Sans GB","Microsoft YaHei",sans-serif}
body{min-height:100vh}
button,input,select{font:inherit}
button{cursor:pointer}
.shell{width:100%;max-width:520px;min-height:100vh;margin:0 auto;background:var(--bg);position:relative;border-left:1px solid rgba(0,0,0,.02);border-right:1px solid rgba(0,0,0,.02)}
.topbar{position:sticky;top:0;z-index:30;height:58px;padding:env(safe-area-inset-top) 12px 0;display:grid;grid-template-columns:44px 1fr 44px;align-items:center;background:rgba(246,247,249,.94);backdrop-filter:blur(16px);border-bottom:1px solid var(--line)}
.topTitle{text-align:center;font-weight:720;font-size:17px;white-space:nowrap;overflow:hidden;text-overflow:ellipsis}.iconbtn{border:0;background:transparent;color:var(--text);height:44px;border-radius:12px;font-size:25px}.iconbtn:active{background:#eceef2}.iconbtn.hidden{visibility:hidden}
#main{padding:14px 14px calc(92px + env(safe-area-inset-bottom))}
.bottomNav{position:fixed;z-index:35;bottom:0;left:50%;transform:translateX(-50%);width:min(520px,100%);height:68px;padding:6px 28px calc(6px + env(safe-area-inset-bottom));display:grid;grid-template-columns:repeat(3,1fr);background:rgba(255,255,255,.97);backdrop-filter:blur(16px);border-top:1px solid var(--line)}
.bottomNav button{border:0;background:transparent;color:#8a8f99;display:flex;flex-direction:column;align-items:center;justify-content:center;gap:1px;font-size:19px}.bottomNav button b{font-size:11px;font-weight:650}.bottomNav button.active{color:var(--primary)}
.hero{padding:10px 2px 4px}.hero h1{margin:0;font-size:27px;line-height:1.25}.hero p{margin:8px 0 0;color:var(--muted);font-size:14px;line-height:1.6}
.subject{width:100%;border:1px solid var(--line);background:var(--card);padding:17px;border-radius:18px;text-align:left;margin-top:12px;box-shadow:var(--shadow)}.subject .row{display:flex;align-items:flex-start;justify-content:space-between;gap:12px}.subject h2{font-size:17px;margin:0}.subject small{color:var(--muted)}.subject .continue{margin-top:16px;width:100%;height:46px;border:0;border-radius:13px;background:var(--primary);color:#fff;font-weight:720}.meter{height:6px;background:#edf0f5;border-radius:99px;margin-top:14px;overflow:hidden}.meter i{display:block;height:100%;background:var(--primary);border-radius:99px}.subjectMeta{display:flex;justify-content:space-between;margin-top:8px;color:var(--muted);font-size:12px}
.sectionTitle{display:flex;align-items:center;justify-content:space-between;margin:22px 2px 10px}.sectionTitle h2{font-size:16px;margin:0}.sectionTitle span{font-size:12px;color:var(--muted)}
.quickGrid{display:grid;grid-template-columns:1fr 1fr;gap:10px}.quick{min-height:82px;border:1px solid var(--line);background:var(--card);border-radius:15px;text-align:left;padding:14px}.quick b{display:block;font-size:15px}.quick span{display:block;color:var(--muted);font-size:12px;margin-top:5px}.quick:active{transform:scale(.99)}
.miniStats{display:grid;grid-template-columns:repeat(3,1fr);gap:8px}.miniStats div{background:var(--card);border:1px solid var(--line);border-radius:14px;padding:12px;text-align:center}.miniStats b{font-size:19px}.miniStats span{display:block;margin-top:3px;color:var(--muted);font-size:11px}
.practiceWrap{padding-bottom:88px}.qHead{display:flex;align-items:center;justify-content:space-between;gap:12px;margin:2px 1px 12px}.qProgress{font-size:13px;color:var(--muted)}.qTags{display:flex;gap:6px;flex-wrap:wrap}.tag{display:inline-flex;padding:5px 8px;border-radius:99px;background:#eef0f4;color:#606672;font-size:11px}.favBtn{border:0;background:transparent;font-size:23px;color:#9a9fa9;padding:6px}.favBtn.on{color:#f0a500}
.questionCard{background:var(--card);border:1px solid var(--line);border-radius:18px;padding:18px;box-shadow:var(--shadow)}.questionCard h1{font-size:20px;line-height:1.55;margin:0 0 18px;font-weight:700}.typeHint{font-size:12px;color:var(--muted);margin-bottom:9px}
.options{display:flex;flex-direction:column;gap:10px}.option{width:100%;display:grid;grid-template-columns:34px 1fr;gap:8px;align-items:start;text-align:left;border:1.5px solid var(--line);background:#fff;border-radius:14px;padding:13px 12px;line-height:1.55;color:var(--text)}.option .letter{width:28px;height:28px;border-radius:50%;border:1px solid #cfd3dc;display:grid;place-items:center;font-weight:700;font-size:13px}.option.selected{border-color:var(--primary);background:var(--primary-soft)}.option.selected .letter{border-color:var(--primary);background:var(--primary);color:#fff}.option.correct{border-color:#82cbb0;background:var(--good-bg)}.option.correct .letter{border-color:var(--good);background:var(--good);color:#fff}.option.wrong{border-color:#efabab;background:var(--bad-bg)}.option.wrong .letter{border-color:var(--bad);background:var(--bad);color:#fff}.option:disabled{opacity:1;color:inherit}
.result{margin-top:12px;border-radius:14px;padding:13px 14px;font-weight:720}.result.good{background:var(--good-bg);color:var(--good)}.result.bad{background:var(--bad-bg);color:var(--bad)}
.explain{margin-top:12px;display:flex;flex-direction:column;gap:10px}.explainBox{background:#fff;border:1px solid var(--line);border-radius:15px;padding:14px}.explainBox h3{margin:0 0 8px;font-size:13px;color:#505662}.explainBox p{margin:0;font-size:14px;line-height:1.7}.explainBox.key{border-color:#d7e2ff;background:#f8faff}.explainBox.memory{border-color:#f4dfaa;background:#fffaf0}.explainBox.teacher{border-color:#d8d7f9;background:#f8f7ff}.explainBox.trap{border-color:#f2d0d0;background:#fff8f8}.explainBox .source{display:block;margin-top:8px;color:var(--muted);font-size:11px}.videoLink{display:inline-flex;margin-top:10px;text-decoration:none;color:var(--primary);font-weight:700;font-size:13px}
.detailToggle{width:100%;border:0;background:transparent;color:var(--primary);padding:10px;font-weight:700}.detailBody.hidden{display:none}
.answerBar{position:fixed;z-index:34;bottom:68px;left:50%;transform:translateX(-50%);width:min(520px,100%);padding:10px 14px;background:linear-gradient(to top,var(--bg) 75%,rgba(246,247,249,0));}.answerBar button{width:100%;height:50px;border:0;border-radius:14px;font-weight:750;font-size:16px}.answerBar .submit{background:var(--primary);color:#fff}.answerBar .submit:disabled{background:#cbd3e6}.answerBar .next{background:#17191f;color:#fff}
.sheetTitle{margin:4px 2px 12px}.sheetTitle h1{font-size:24px;margin:0}.sheetTitle p{color:var(--muted);font-size:13px;line-height:1.6}.filterRow{display:flex;gap:8px;overflow:auto;padding-bottom:4px}.pill{white-space:nowrap;border:1px solid var(--line);background:#fff;border-radius:99px;padding:9px 13px;font-size:13px}.pill.active{background:#17191f;color:#fff;border-color:#17191f}
.chapterList{display:flex;flex-direction:column;gap:9px}.chapterBtn{border:1px solid var(--line);background:#fff;border-radius:15px;padding:14px;text-align:left}.chapterBtn b{display:block;font-size:14px;line-height:1.45}.chapterBtn span{display:block;color:var(--muted);font-size:12px;margin-top:6px}
.empty{background:#fff;border:1px solid var(--line);border-radius:16px;padding:30px 20px;text-align:center;color:var(--muted)}.empty b{display:block;color:var(--text);font-size:16px;margin-bottom:7px}
.wrongList{display:flex;flex-direction:column;gap:9px}.wrongItem{background:#fff;border:1px solid var(--line);border-radius:15px;padding:14px}.wrongItem .meta{font-size:11px;color:var(--muted)}.wrongItem p{font-size:14px;line-height:1.55;margin:7px 0 0}.wrongItem button{margin-top:10px;border:0;background:var(--primary-soft);color:var(--primary);border-radius:10px;padding:8px 11px;font-weight:700}
.primaryWide{width:100%;height:48px;border:0;border-radius:14px;background:var(--primary);color:#fff;font-weight:750;margin-bottom:12px}.secondaryWide{width:100%;height:46px;border:1px solid var(--line);border-radius:14px;background:#fff;color:var(--text);font-weight:700}
.meCard{background:#fff;border:1px solid var(--line);border-radius:17px;padding:16px;margin-bottom:10px}.meCard h3{margin:0 0 12px;font-size:15px}.statLine{display:flex;justify-content:space-between;padding:9px 0;border-bottom:1px solid #f0f1f4}.statLine:last-child{border-bottom:0}.statLine span{color:var(--muted);font-size:13px}.statLine b{font-size:13px}.profileBtns{display:flex;gap:8px;flex-wrap:wrap}.profileBtns button{border:1px solid var(--line);background:#fff;border-radius:11px;padding:9px 11px}.profileBtns button.active{border-color:var(--primary);color:var(--primary);background:var(--primary-soft)}
.toast{position:fixed;z-index:99;left:50%;bottom:150px;transform:translateX(-50%) translateY(10px);background:#17191f;color:#fff;padding:9px 13px;border-radius:10px;font-size:13px;opacity:0;pointer-events:none;transition:.2s}.toast.show{opacity:1;transform:translateX(-50%) translateY(0)}
@media(min-width:720px){body{padding:18px 0}.shell{min-height:calc(100vh - 36px);border-radius:24px;overflow:hidden;box-shadow:0 18px 60px rgba(0,0,0,.08)}.bottomNav,.answerBar{position:fixed}.topbar{top:18px}}
.explainBox .statLine{display:block;padding:9px 0}.explainBox .statLine span{display:block;color:var(--text);font-size:13px;line-height:1.5}.explainBox .statLine b{display:block;margin-top:4px;color:var(--muted);font-weight:500;line-height:1.5}