:root{font-family:system-ui,Avenir,Helvetica,Arial,sans-serif;line-height:1.5;font-weight:400;color-scheme:light dark;color:#213547;background-color:#fff}body{margin:0;min-width:320px;min-height:100vh}#app{max-width:800px;margin:0 auto;padding:2rem}.question-card{background:#fff;border-radius:8px;box-shadow:0 2px 4px #0000001a;padding:2rem;margin-bottom:2rem}.options{display:flex;flex-direction:column;gap:1rem;margin:1.5rem 0}.option{padding:1rem;border:1px solid #e2e8f0;border-radius:4px;cursor:pointer;transition:all .2s}.option:hover{background-color:#f8fafc}.option.selected{background-color:#e2e8f0}.option.correct{background-color:#dcfce7;border-color:#86efac}.option.incorrect{background-color:#fee2e2;border-color:#fca5a5}.explanation{margin-top:1.5rem;padding:1rem;background-color:#f8fafc;border-radius:4px;display:none}.explanation.visible{display:block}.controls{display:flex;justify-content:space-between;margin-top:2rem}button{background-color:#3b82f6;color:#fff;border:none;padding:.5rem 1rem;border-radius:4px;cursor:pointer;font-size:1rem}button:hover{background-color:#2563eb}button:disabled{background-color:#94a3b8;cursor:not-allowed}.progress{text-align:center;margin-bottom:1rem;color:#64748b}.score{text-align:center;font-size:1.2rem;margin-bottom:1rem}