:root{--ink:#172033;--muted:#718096;--line:#e6eaf0;--paper:#fff;--bg:#f5f7fb;--accent:#2563eb;--accent-soft:#eaf1ff;--green:#159570;--red:#d94c5c;--amber:#c68016}*{box-sizing:border-box}body{margin:0;background:var(--bg);color:var(--ink);font:14px/1.6 -apple-system,BlinkMacSystemFont,"Segoe UI","PingFang SC","Hiragino Sans GB",Arial,sans-serif}.topbar{height:72px;background:#fff;border-bottom:1px solid var(--line);display:flex;align-items:center;justify-content:space-between;padding:0 30px}.brand{display:flex;align-items:center;gap:11px}.brand-mark{width:34px;height:34px;display:grid;place-items:center;background:var(--ink);color:#fff;font-size:12px;font-weight:800;letter-spacing:.5px}.brand strong{display:block;font-size:16px;line-height:1.2}.brand small{display:block;color:var(--muted);font-size:11px;margin-top:3px}.top-actions{display:flex;align-items:center;gap:10px}.stat-chip{display:flex;align-items:center;gap:8px;padding:6px 13px;background:#f6f8fb;border:1px solid var(--line);font-size:12px;color:var(--muted)}.stat-chip b{font-size:15px;color:var(--ink)}.icon-btn{border:1px solid var(--line);background:#fff;width:34px;height:34px;font-size:18px;color:var(--muted);cursor:pointer}.layout{display:grid;grid-template-columns:230px minmax(460px,1fr) 245px;gap:26px;max-width:1440px;margin:0 auto;padding:28px 30px}.sidebar{min-height:calc(100vh - 128px);display:flex;flex-direction:column}.side-section{margin-bottom:30px}.section-label{font-size:11px;letter-spacing:1.2px;text-transform:uppercase;color:#9aa5b5;margin:0 0 10px 12px}.nav-btn{width:100%;height:42px;border:0;background:transparent;color:#556176;display:flex;align-items:center;justify-content:space-between;padding:0 12px;margin:3px 0;cursor:pointer;text-align:left}.nav-btn:hover{background:#eef3fb}.nav-btn.active{background:var(--accent-soft);color:var(--accent);font-weight:650}.nav-btn em{font-style:normal;color:#a5afbe;font-size:12px}.nav-btn.active em{color:var(--accent)}.switch-row{height:40px;display:flex;align-items:center;justify-content:space-between;padding:0 12px;color:#556176}.switch-row input{display:none}.switch-row i{width:34px;height:19px;border-radius:20px;background:#d7dde7;position:relative;cursor:pointer;transition:.2s}.switch-row i:after{content:"";width:15px;height:15px;border-radius:50%;background:#fff;position:absolute;top:2px;left:2px;box-shadow:0 1px 3px #aeb8c8;transition:.2s}.switch-row input:checked+i{background:var(--accent)}.switch-row input:checked+i:after{left:17px}.side-footer{margin-top:auto;color:#98a3b4;font-size:11px;display:flex;align-items:center;gap:7px;padding:0 12px 5px}.dot{width:6px;height:6px;border-radius:50%;background:var(--green)}.content{min-width:0}.practice-head{display:flex;justify-content:space-between;align-items:flex-end;margin:6px 0 19px}.eyebrow{font-size:12px;color:var(--accent);font-weight:650;margin:0 0 3px}.practice-head h1{font-size:25px;margin:0;letter-spacing:0}.progress-wrap{width:180px;text-align:right;color:var(--muted);font-size:12px}.progress{height:5px;background:#e2e7ef;margin-top:7px}.progress i{display:block;height:100%;background:var(--accent);width:0;transition:.25s}.question-card{background:var(--paper);border:1px solid var(--line);padding:31px 34px 28px;min-height:430px}.question-meta{display:flex;align-items:center;gap:9px;margin-bottom:19px}.q-index{font-size:12px;color:#8994a5}.type-tag{font-size:11px;padding:2px 8px;background:#f0f4fa;color:#64748b}.question-title{font-size:18px;line-height:1.75;font-weight:650;margin:0 0 24px;letter-spacing:.1px}.options{display:flex;flex-direction:column;gap:11px}.option{border:1px solid var(--line);min-height:49px;display:flex;align-items:center;padding:11px 14px;gap:12px;cursor:pointer;transition:.15s;background:#fff}.option:hover{border-color:#b4c8f2;background:#f9fbff}.option.selected{border-color:var(--accent);background:var(--accent-soft)}.option.correct{border-color:var(--green);background:#effaf6}.option.incorrect{border-color:var(--red);background:#fff2f3}.option input{display:none}.option-key{width:25px;height:25px;border:1px solid #cbd4e1;display:grid;place-items:center;color:#718096;font-size:12px;flex:0 0 auto}.option.selected .option-key{background:var(--accent);border-color:var(--accent);color:#fff}.option.correct .option-key{background:var(--green);border-color:var(--green);color:#fff}.option.incorrect .option-key{background:var(--red);border-color:var(--red);color:#fff}.option-text{color:#344054}.result-note{margin-top:22px;border-top:1px solid var(--line);padding-top:16px;font-size:13px;color:var(--muted)}.result-note strong{color:var(--green)}.result-note.error strong{color:var(--red)}.bottom-actions{display:flex;justify-content:center;gap:10px;margin:20px 0}.primary-btn,.secondary-btn{height:42px;padding:0 22px;border:1px solid transparent;font-size:14px;cursor:pointer}.primary-btn{background:var(--accent);color:#fff}.primary-btn:hover{background:#1d4ed8}.secondary-btn{background:#fff;border-color:var(--line);color:#556176}.secondary-btn:hover{border-color:#b5c5df}.secondary-btn:disabled,.primary-btn:disabled{opacity:.45;cursor:not-allowed}.palette-panel{background:#fff;border:1px solid var(--line);height:max-content;padding:18px}.palette-head{display:flex;justify-content:space-between;align-items:center}.palette-head strong{font-size:14px}.palette-head span{font-size:12px;color:var(--muted)}.legend{display:flex;gap:12px;margin:15px 0 13px;color:#8994a5;font-size:11px}.legend span{display:flex;align-items:center;gap:5px}.legend-dot{display:inline-block;width:8px;height:8px;background:#e2e7ef}.legend-dot.current{background:var(--accent)}.legend-dot.done{background:#9bb8f4}.legend-dot.wrong{background:#ec8993}.palette{display:grid;grid-template-columns:repeat(5,1fr);gap:6px;max-height:calc(100vh - 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