:root{--bg: #f7f7f8;--card: #fff;--ink: #1c1c1e;--muted: #8e8e93;--brand: #4f46e5;--danger: #e5484d;--ok: #30a46c;--warn: #f5a623;--radius: 14px}*{box-sizing:border-box}body{margin:0;background:var(--bg);color:var(--ink);font-family:system-ui,-apple-system,PingFang SC,Microsoft YaHei,sans-serif}#app{max-width:520px;margin:0 auto;min-height:100dvh;display:flex;flex-direction:column}.topbar{display:flex;align-items:center;justify-content:space-between;padding:12px 16px}.logo{font-weight:700;font-size:18px}main{flex:1;padding:0 16px 84px}.tabbar{position:fixed;bottom:0;left:50%;transform:translate(-50%);width:100%;max-width:520px;display:flex;background:var(--card);border-top:1px solid #e5e5ea}.tabbar button{flex:1;border:0;background:none;padding:10px 0 12px;font-size:12px;color:var(--muted)}.tabbar button.active{color:var(--brand)}.tabbar .ico{display:block;font-size:20px;margin-bottom:2px}.card{background:var(--card);border-radius:var(--radius);padding:16px;margin-bottom:12px;box-shadow:0 1px 2px #0000000a}.btn{display:block;width:100%;border:0;border-radius:var(--radius);padding:14px;font-size:16px;background:var(--brand);color:#fff;margin-top:10px}.btn.secondary{background:#ececf1;color:var(--ink)}.btn.danger{background:var(--danger);color:#fff}.btn:disabled{opacity:.5}input,textarea,select{width:100%;border:1px solid #d9d9de;border-radius:10px;padding:10px 12px;font-size:16px;margin-bottom:10px;background:#fff}.muted{color:var(--muted);font-size:13px}.toast{position:fixed;bottom:96px;left:50%;transform:translate(-50%);background:#333;color:#fff;padding:10px 18px;border-radius:20px;font-size:14px;z-index:70}.sync-badge{font-size:12px;color:var(--muted)}.progress{height:8px;background:#ececf1;border-radius:4px;overflow:hidden;margin:10px 0}.progress>div{height:100%;background:var(--brand);transition:width .3s}.overlay{position:fixed;top:0;right:0;bottom:0;left:0;background:var(--bg);z-index:50;display:flex;flex-direction:column;padding:16px}.overlay .card{flex:1;display:flex;flex-direction:column;justify-content:center;text-align:center;font-size:22px;animation:fadein .2s ease}@keyframes fadein{0%{opacity:0}to{opacity:1}}.choices button{display:block;width:100%;margin-bottom:10px;text-align:left}.grade-row{display:flex;gap:8px;margin-top:16px}.grade-row button{flex:1;border:0;border-radius:12px;padding:14px 0;font-size:15px}.grade-0{background:var(--danger);color:#fff}.grade-1{background:var(--warn);color:#fff}.grade-2{background:var(--ok);color:#fff}.word-card{display:flex;justify-content:space-between;align-items:center}.pill{font-size:12px;padding:2px 8px;border-radius:10px;background:#ececf1}.sheet{position:fixed;top:0;right:0;bottom:0;left:0;background:#00000059;z-index:60;display:flex;align-items:flex-end}.sheet .inner{background:var(--bg);width:100%;max-width:520px;margin:0 auto;border-radius:16px 16px 0 0;padding:16px;max-height:85dvh;overflow:auto}.row{display:flex;gap:10px}.row>*{flex:1}