:root{color-scheme:light;--blue:#165a84;--deep:#123f5d;--sky:#eaf5fc;--line:#b9d8e9;--ink:#16384d;--muted:#557284;--soft:#f7fbfe}*{box-sizing:border-box}body{margin:0;background:#f3f9fc;color:var(--ink);font-family:"Noto Sans SC","PingFang SC","Microsoft YaHei",system-ui,sans-serif;line-height:1.55}a{color:var(--deep)}h1,h2,h3{line-height:1.22}.hero,.card{width:min(880px,100%);background:#fff;border:1px solid var(--line);border-radius:22px;box-shadow:0 8px 24px #123f5d14;padding:22px}.eyebrow{font-weight:900;color:var(--blue)}.sub{color:var(--muted)}.badge{display:inline-block;padding:3px 10px;border-radius:999px;background:var(--sky);color:var(--deep);font-size:.84rem;font-weight:900}.learning-path{display:grid;grid-template-columns:repeat(auto-fit,minmax(135px,1fr));gap:8px;margin:10px 0}.learning-path div{padding:10px;border-radius:12px;background:var(--sky);font-weight:800;text-align:center}.example{padding:11px 14px;border-left:5px solid var(--blue);background:var(--soft);border-radius:12px;margin:10px 0}.question{padding:12px;border:1px solid var(--line);border-radius:16px;background:var(--soft)}.practice-question{font-size:1.08rem;font-weight:800}.options{display:grid;gap:6px}.answer{width:100%;min-height:48px;border-radius:13px;border:2px solid var(--blue);background:#fff;color:var(--deep);font:inherit;font-weight:850;padding:8px 14px;text-align:left;cursor:pointer}.answer:hover{background:var(--sky)}.answer.correct{background:#dff4e7;border-color:#21864f}.answer.wrong{background:#fff0dd;border-color:#b66e0a}.feedback{min-height:40px;padding:8px 12px;border-radius:11px;background:#edf3f7;margin-top:8px}.feedback.success{background:#dff4e7}.feedback.hint{background:#fff0dd}.unit-link,.chapter-link{display:block;padding:16px;border:1px solid var(--line);border-radius:16px;background:#fff;text-decoration:none}.unit-link h3,.chapter-link h3{margin:4px 0}.unit-link p,.chapter-link p{margin:4px 0;color:var(--muted)}.menu-card{width:min(680px,100%)}.btn-link{display:inline-flex;align-items:center;justify-content:center;text-decoration:none;margin-top:8px}@media(max-width:700px){.hero,.card{padding:12px}.v2-main h2{margin:6px 0}.learning-path{gap:5px}.learning-path div{padding:7px;font-size:.88rem}.question{padding:8px}.practice-question{font-size:1rem;line-height:1.4}.options{gap:4px}.answer{min-height:43px;padding:6px 10px;line-height:1.35}.feedback{min-height:36px;padding:6px 10px;margin-top:6px}.example{padding:8px 10px}.v2-main p{margin:5px 0}}