:root{--bg:#0b0f14;--panel:#0f1620;--line:#23303d;--text:#e6edf5;--muted:#8fa1b3;--accent:#6ea8fe}
*{box-sizing:border-box}body{margin:0;background:var(--bg);color:var(--text);font:14px/1.45 system-ui,-apple-system,Segoe UI,sans-serif;overflow:hidden}
.pr-head{height:56px;display:flex;align-items:center;gap:16px;padding:0 20px;background:#0d141d;border-bottom:1px solid var(--line)}.pr-brand{color:var(--accent);font-weight:800;text-decoration:none}.pr-route{font-weight:700}.pr-head nav{margin-left:auto;display:flex;gap:14px}.pr-head nav a{color:var(--muted);text-decoration:none;font-size:12px}.pr-head nav a.on{color:var(--text)}
.pr-main{height:calc(100dvh - 56px);display:grid;grid-template-columns:300px minmax(0,1fr)}.pr-rail{background:#0d141d;border-right:1px solid var(--line);padding:14px;overflow:auto}.pr-rail label{display:flex;flex-direction:column;gap:4px;font-size:11px;color:var(--muted)}.pr-rail select{background:#0a1118;color:var(--text);border:1px solid var(--line);border-radius:7px;padding:6px}.pr-label{margin:14px 0 8px;font-size:10px;letter-spacing:.1em;text-transform:uppercase;color:var(--muted)}.pr-list{display:flex;flex-direction:column;gap:3px}.pr-item{text-align:left;background:#101923;border:1px solid transparent;color:var(--text);border-radius:7px;padding:7px 8px;cursor:pointer;font-size:12px}.pr-item.on{border-color:var(--accent);background:#142235}.pr-item span{display:block;color:var(--muted);font-size:10px}
.pr-focus{display:flex;flex-direction:column;min-height:0;padding:22px 26px 0}.pr-title{min-height:56px;color:var(--muted);font-size:13px}.pr-title b{display:block;color:var(--text);font-size:21px}.pr-body{flex:1;overflow:auto;max-width:840px;padding-bottom:20px}.pr-math{background:#0d1620;border:1px solid var(--line);border-radius:12px;padding:18px;overflow:auto;margin-bottom:14px}.pr-statement{color:#c9d6e3;font-size:13px;line-height:1.6}.pr-q{font-weight:700;margin:16px 0 8px}.pr-opt{display:block;width:100%;text-align:left;background:#101923;border:1px solid var(--line);color:var(--text);border-radius:9px;padding:10px 12px;margin-bottom:7px;cursor:pointer}.pr-opt.correct{border-color:#2f7d52;background:#123524}.pr-opt.wrong{border-color:#8a3038;background:#3a1418}.pr-foot{height:60px;display:flex;align-items:center;gap:12px;border-top:1px solid var(--line);color:var(--muted);font-size:12px}.pr-foot button{background:#162231;color:var(--text);border:1px solid var(--line);border-radius:8px;padding:7px 12px;cursor:pointer}.pr-foot #pr-next{margin-left:auto}
@media(max-width:760px){.pr-head nav{display:none}.pr-main{grid-template-columns:minmax(0,1fr)}.pr-rail{display:none}.pr-focus{padding:16px 12px}.pr-body{max-width:100%}.pr-title b{font-size:18px}.pr-opt{padding:9px}}