:root{--primary:#5b5fef;--primary-dark:#4649c9;--accent:#8e6fbf;--bg:#f5f6fb;--card:#ffffff;--text:#23243a;--text-2:#6b6e85;--text-3:#9b9eb5;--line:#e9eaf3;--green:#1fa56a;--red:#e14b5a;--orange:#f08c2e;--radius:16px;--shadow:0 2px 12px rgba(35,36,58,0.06)}*{box-sizing:border-box;-webkit-tap-highlight-color:transparent}body,html{margin:0;padding:0;background:var(--bg);color:var(--text);font-family:-apple-system,BlinkMacSystemFont,PingFang SC,Hiragino Sans GB,Microsoft YaHei,Segoe UI,Roboto,sans-serif;font-size:16px;line-height:1.55}a{color:inherit;text-decoration:none}button{font-family:inherit;border:none;cursor:pointer}input,select,textarea{font-family:inherit;font-size:16px;color:var(--text);outline:none}.page{max-width:520px;margin:0 auto;padding:0 16px 96px;min-height:100vh}.topbar{position:-webkit-sticky;position:sticky;top:0;z-index:20;background:linear-gradient(135deg,var(--primary),var(--accent));color:#fff;margin:0 -16px;padding:18px 16px 16px;border-radius:0 0 22px 22px;box-shadow:0 4px 18px rgba(91,95,239,.25)}.topbar h1{margin:0;font-size:21px;font-weight:700}.topbar .sub{font-size:13px;opacity:.85;margin-top:2px}.topbar .back{display:inline-flex;align-items:center;gap:6px;font-size:14px;opacity:.9;margin-bottom:6px}.card{background:var(--card);border-radius:var(--radius);box-shadow:var(--shadow);padding:16px;margin:14px 0}.btn{display:inline-flex;align-items:center;justify-content:center;gap:8px;border-radius:12px;padding:12px 18px;font-size:15px;font-weight:600;transition:transform .08s ease,opacity .15s}.btn:active{transform:scale(.97)}.btn:disabled{opacity:.5;cursor:not-allowed}.btn-primary{background:linear-gradient(135deg,var(--primary),var(--accent));color:#fff;box-shadow:0 4px 14px rgba(91,95,239,.3)}.btn-ghost{background:#f0f1f8;color:var(--text)}.btn-danger{background:#fdecee;color:var(--red)}.btn-block{width:100%}.btn-sm{padding:8px 14px;font-size:13px;border-radius:10px}.badge{display:inline-flex;align-items:center;gap:4px;font-size:12px;padding:3px 10px;border-radius:999px;font-weight:500}.badge-gray{background:#eef0f6;color:var(--text-2)}.badge-green{background:#e5f7ef;color:var(--green)}.badge-red{background:#fdecee;color:var(--red)}.badge-orange{background:#fef3e6;color:var(--orange)}.badge-primary{background:#ecedfe;color:var(--primary)}.section-title{font-size:15px;font-weight:700;margin:18px 0 10px;display:flex;align-items:center;gap:8px}.empty{text-align:center;color:var(--text-3);padding:40px 16px;font-size:14px}.empty .icon{font-size:44px;margin-bottom:10px}.spinner{width:22px;height:22px;border:3px solid rgba(255,255,255,.35);border-top-color:#fff;border-radius:50%;animation:spin .8s linear infinite;display:inline-block}.spinner.dark{border-color:rgba(91,95,239,.2);border-top-color:var(--primary)}@keyframes spin{to{transform:rotate(1turn)}}.loading-box{text-align:center;padding:36px 16px;color:var(--text-2);font-size:14px;display:flex;flex-direction:column;align-items:center;gap:12px}.chip{display:inline-flex;align-items:center;gap:6px;background:#f0f1f8;color:var(--text);border-radius:999px;padding:8px 14px;font-size:13px}.chip-row{display:flex;flex-wrap:wrap;gap:8px;margin-top:10px}.bottom-nav{position:fixed;bottom:0;left:0;right:0;background:rgba(255,255,255,.94);-webkit-backdrop-filter:blur(12px);backdrop-filter:blur(12px);border-top:1px solid var(--line);display:flex;z-index:30;padding-bottom:env(safe-area-inset-bottom)}.bottom-nav a{flex:1 1;text-align:center;padding:10px 0 8px;color:var(--text-3);font-size:11px;display:flex;flex-direction:column;align-items:center;gap:2px}.bottom-nav a .nav-icon{font-size:22px}.bottom-nav a.active{color:var(--primary);font-weight:600}.quiz-option{display:block;width:100%;text-align:left;background:var(--card);border:2px solid var(--line);border-radius:14px;padding:14px 16px;margin:10px 0;font-size:15px;color:var(--text)}.quiz-option.picked{border-color:var(--primary);background:#f3f3ff}.quiz-option.correct{border-color:var(--green);background:#e9f9f1}.quiz-option.wrong{border-color:var(--red);background:#fdecee}input[type=number],input[type=text],select,textarea{width:100%;border:2px solid var(--line);border-radius:12px;padding:12px 14px;background:#fff}textarea{min-height:84px;resize:vertical}label.field{display:block;font-size:13px;color:var(--text-2);margin:14px 0 6px;font-weight:600}.toast{position:fixed;left:50%;bottom:96px;transform:translateX(-50%);background:rgba(35,36,58,.92);color:#fff;padding:10px 20px;border-radius:999px;font-size:14px;z-index:50;animation:fadein .2s ease}@keyframes fadein{0%{opacity:0;transform:translate(-50%,8px)}to{opacity:1;transform:translate(-50%)}}.chat-list{display:flex;flex-direction:column;gap:12px;padding-bottom:90px}.chat-msg{max-width:86%;padding:12px 14px;border-radius:16px;font-size:15px;white-space:pre-wrap;word-break:break-word}.chat-msg.user{align-self:flex-end;background:linear-gradient(135deg,var(--primary),var(--accent));color:#fff;border-bottom-right-radius:4px}.chat-msg.ai{align-self:flex-start;background:var(--card);box-shadow:var(--shadow);border-bottom-left-radius:4px}.chat-input-bar{position:fixed;bottom:62px;left:50%;transform:translateX(-50%);width:100%;max-width:520px;padding:8px 12px;background:rgba(245,246,251,.96);display:flex;gap:8px;z-index:25}.chat-input-bar input{flex:1 1}.slide-card{background:#fff;border-radius:14px;box-shadow:var(--shadow);overflow:hidden;margin:12px 0}.slide-head{background:linear-gradient(135deg,var(--primary),var(--accent));color:#fff;padding:12px 16px;font-weight:700;font-size:16px}.slide-body{padding:14px 16px}.slide-body ul{margin:0;padding-left:18px}.slide-body li{margin:8px 0;font-size:14px}.slide-note{font-size:12px;color:var(--text-2);background:#f7f7fb;border-radius:10px;padding:10px 12px;margin-top:10px;font-style:italic}.slide-img{width:100%;aspect-ratio:16/9;object-fit:cover;background:#eef0f6}@media (min-width:521px){.page{max-width:560px}}