:root {
    --violet:#8b7bff; --indigo:#6366f1; --cyan:#38e0d0; --pink:#ff7eb6;
    --bg:#07061a; --bg2:#0d0b28;
    --text:#e9e7ff; --muted:#9d97c9;
    --card:rgba(255,255,255,.05); --border:rgba(255,255,255,.10);
    --primary-color:#8b7bff; --secondary-color:#6366f1; --accent-color:#ff7eb6;
    --dark-color:#e9e7ff; --light-color:#07061a;
}

* { margin:0; padding:0; box-sizing:border-box;
    font-family:'Inter',-apple-system,BlinkMacSystemFont,'Segoe UI',Roboto,'PingFang SC','Microsoft YaHei',sans-serif; }

body {
    color:var(--text); line-height:1.6; min-height:100vh; display:flex; flex-direction:column;
    background:radial-gradient(1100px 700px at 75% -10%,rgba(139,123,255,.18),transparent 60%),
               radial-gradient(900px 700px at 10% 110%,rgba(56,224,208,.12),transparent 55%),
               linear-gradient(180deg,var(--bg),var(--bg2));
    background-attachment:fixed;
}

.container { max-width:1200px; margin:0 auto; padding:0 20px; flex:1; display:flex; flex-direction:column; width:100%; }

header { padding:30px 0 10px; text-align:center; }
.logo { font-size:2.6rem; font-weight:800; letter-spacing:-1px; margin-bottom:10px;
    background:linear-gradient(120deg,#fff,var(--violet) 50%,var(--cyan));
    -webkit-background-clip:text; background-clip:text; -webkit-text-fill-color:transparent;
    text-shadow:0 0 50px rgba(139,123,255,.35); }
.tagline { font-size:1.15rem; color:var(--muted); margin-bottom:30px; }

.main-content { text-align:center; padding:10px 0; }
h1 { font-size:clamp(2rem,5vw,3rem); margin-bottom:18px; line-height:1.2;
    background:linear-gradient(120deg,#fff,var(--violet));
    -webkit-background-clip:text; background-clip:text; color:transparent; }
.description { max-width:700px; margin:0 auto 36px; font-size:1.08rem; color:var(--muted); }

.cta-button { display:inline-block; background:linear-gradient(120deg,var(--indigo),var(--violet));
    color:#fff; padding:14px 38px; font-size:1.1rem; font-weight:700; border-radius:50px;
    text-decoration:none; border:none; cursor:pointer; transition:all .3s ease;
    box-shadow:0 10px 30px -8px rgba(99,102,241,.6); margin-bottom:28px; }
.cta-button:hover { transform:translateY(-3px); box-shadow:0 16px 40px -8px rgba(139,123,255,.8); }
.cta-button:active { transform:translateY(1px); }

/* 聊天界面 */
.chat-container { max-width:820px; margin:0 auto; width:100%; border-radius:18px; overflow:hidden;
    background:rgba(13,11,40,.6); border:1px solid var(--border); backdrop-filter:blur(14px);
    box-shadow:0 20px 60px -20px rgba(0,0,0,.7); display:flex; flex-direction:column;
    position:relative; min-height:80px; max-height:95vh; transition:all .3s ease; }
.chat-container.expanded { height:auto; min-height:220px; }

.chat-header { background:linear-gradient(120deg,rgba(99,102,241,.35),rgba(139,123,255,.35));
    color:#fff; padding:15px 20px; font-size:1.15rem; font-weight:700; cursor:pointer;
    display:flex; justify-content:space-between; align-items:center; user-select:none;
    border-bottom:1px solid var(--border); }
.chat-header .expand-icon { transition:transform .3s ease; }
.chat-container.expanded .chat-header .expand-icon { transform:rotate(180deg); }

.chat-messages { flex:1; padding:22px; overflow-y:auto; display:flex; flex-direction:column;
    gap:14px; align-items:flex-start; position:relative; max-height:calc(95vh - 130px); }

.message { max-width:82%; padding:12px 16px; border-radius:18px; line-height:1.5; word-wrap:break-word;
    text-align:left; opacity:0; transform:translateY(10px); animation:fadeInUp .3s ease forwards; position:relative; }
@keyframes fadeInUp { to { opacity:1; transform:translateY(0); } }

.message:hover .message-actions { opacity:1; }
.message-actions { position:absolute; top:-20px; right:0; display:flex; gap:8px; opacity:0;
    transition:opacity .2s ease; background:rgba(13,11,40,.95); padding:2px 6px; border-radius:12px;
    border:1px solid var(--border); box-shadow:0 4px 14px rgba(0,0,0,.4); }
.message-action-btn { cursor:pointer; padding:2px 6px; font-size:.9rem; color:var(--muted); opacity:.8;
    transition:all .2s ease; border:none; background:none; border-radius:4px; }
.message-action-btn:hover { opacity:1; background:rgba(255,255,255,.08); }
.message-action-btn.edit-btn:hover { color:var(--violet); }
.message-action-btn.delete-btn:hover { color:#ff6b6b; }
.message-action-btn.resend-btn:hover { color:var(--cyan); }

.message.editing { background:rgba(139,123,255,.14); }
.message.editing .message-content { display:none; }
.message-edit-input { width:100%; padding:8px 12px; border:1px solid var(--violet); border-radius:12px;
    font-size:1rem; line-height:1.4; resize:vertical; min-height:60px; margin-bottom:8px;
    background:rgba(0,0,0,.3); color:var(--text); }
.message-edit-actions { display:flex; gap:8px; justify-content:flex-end; }
.message-edit-btn { padding:4px 12px; border:none; border-radius:6px; cursor:pointer; font-size:.9rem; transition:all .2s ease; }
.message-edit-btn.save { background:var(--violet); color:#fff; }
.message-edit-btn.cancel { background:rgba(255,255,255,.12); color:var(--text); }
.message-edit-btn:hover { opacity:.9; }

.user-message { align-self:flex-end; background:linear-gradient(120deg,var(--indigo),var(--violet));
    color:#fff; border-bottom-right-radius:5px; animation-delay:.05s;
    box-shadow:0 6px 20px -8px rgba(99,102,241,.7); }
.bot-message { align-self:flex-start; background:rgba(255,255,255,.06); color:var(--text);
    border:1px solid var(--border); border-bottom-left-radius:5px; }

.chat-input-container { display:flex; padding:15px; background:rgba(7,6,26,.6); border-top:1px solid var(--border);
    opacity:0; height:0; overflow:hidden; transition:all .3s ease; position:relative; }
.chat-container.expanded .chat-input-container { opacity:1; height:auto; min-height:60px; }
.resize-handle, .resize-handle:hover, .resize-handle::after { display:none; }

.chat-input { flex:1; padding:12px 16px; border:1px solid var(--border); border-radius:25px;
    font-size:1rem; outline:none; transition:border .3s,box-shadow .3s; background:rgba(255,255,255,.05); color:var(--text); }
.chat-input::placeholder { color:var(--muted); }
.chat-input:focus { border-color:var(--violet); box-shadow:0 0 0 3px rgba(139,123,255,.2); }

.send-button { margin-left:10px; padding:12px 24px; background:linear-gradient(120deg,var(--indigo),var(--violet));
    color:#fff; border:none; border-radius:25px; cursor:pointer; font-weight:700; transition:all .3s; }
.send-button:hover { transform:translateY(-1px); box-shadow:0 8px 22px -8px rgba(139,123,255,.8); }
.send-button:disabled { opacity:.5; cursor:not-allowed; transform:none; box-shadow:none; }

.typing-indicator { display:none; align-self:flex-start; padding:10px 16px; background:rgba(255,255,255,.06);
    border:1px solid var(--border); border-radius:18px; color:var(--muted); font-style:italic;
    margin-bottom:14px; animation:pulse 1.5s infinite; }
@keyframes pulse { 0%,100%{opacity:.55} 50%{opacity:1} }
.initial-message { padding:15px; text-align:center; color:var(--muted); }

footer { text-align:center; padding:30px 0; color:var(--muted); font-size:.9rem; margin-top:auto; }
footer a { color:var(--violet); text-decoration:none; }
footer a:hover { text-decoration:underline; }

.header-buttons { display:flex; gap:15px; align-items:center; }
.maximize-icon { cursor:pointer; font-size:1.1rem; opacity:.8; transition:all .3s ease; padding:2px 5px; border-radius:4px; }
.maximize-icon:hover { opacity:1; background:rgba(255,255,255,.12); }

.chat-container.maximized { position:fixed; inset:0; z-index:1000; border-radius:0; margin:0;
    max-width:100%; height:100vh; max-height:100vh; background:linear-gradient(180deg,var(--bg),var(--bg2)); }
.chat-container.maximized .chat-messages { max-height:calc(100vh - 130px); }
.chat-container.maximized .chat-input-container { position:absolute; bottom:0; left:0; right:0; background:rgba(7,6,26,.85); border-top:1px solid var(--border); }

@media (max-width:768px) {
    h1 { font-size:2.2rem; }
    .description { font-size:1rem; padding:0 20px; }
    .logo { font-size:2rem; }
    .tagline { font-size:1rem; }
    .chat-container.expanded { min-height:180px; }
    .chat-messages { max-height:calc(95vh - 120px); }
    .chat-container.maximized .chat-messages { max-height:calc(100vh - 120px); }
    .header-buttons { gap:10px; }
    .maximize-icon { font-size:1rem; }
}

@media (prefers-reduced-motion: reduce) {
    * { animation:none!important; transition:none!important; }
    .message { opacity:1; transform:none; }
}