:root {
    --bg-color: #ffffff;
    --text-primary: #1f1f1f;
    --text-secondary: #5f6368;
    --accent: #0052cc;
    --accent-hover: #003d99;
    --surface: #f8f9fa;
    --chip-bg: #f1f3f4;
    --chip-border: #e0e0e0;
}

@media (prefers-color-scheme: dark) {
    :root {
        --bg-color: #000000;
        --text-primary: #ffffff;
        --text-secondary: #a0a0a0;
        --accent: #4dabf7;
        --accent-hover: #339af0;
        --surface: #1e1e1e;
        --chip-bg: rgba(255, 255, 255, 0.15); 
        --chip-border: rgba(255, 255, 255, 0.2);
    }
}

* { box-sizing: border-box; margin: 0; padding: 0; font-family: "Google Sans", sans-serif; -webkit-tap-highlight-color: transparent; }

body { 
    background-color: var(--bg-color); 
    color: var(--text-primary); 
    min-height: 100vh; 
    width: 100%; 
    display: flex; 
    flex-direction: column; 
    overflow-x: hidden; 
}

/* 导航栏 */
.navbar { 
    display: flex; 
    justify-content: space-between; 
    align-items: center; 
    width: 100%; 
    position: fixed; 
    top: 0; left: 0; 
    z-index: 10001; 
    padding: 20px 24px;
    background: transparent;
}
.logo { font-weight: 800; font-size: 1.2rem; }
.lang-switch { font-weight: 700; cursor: pointer; padding: 10px; opacity: 0.8; }

/* 主视觉区 (修复居中问题) */
.hero-container { 
    flex: 1; 
    display: flex; 
    flex-direction: column; 
    justify-content: center; /* 垂直居中 */
    align-items: center;     /* 水平居中 */
    text-align: center; 
    padding: 0 20px;
    width: 100%;
}

.content-wrapper { 
    max-width: 800px; 
    width: 100%;
    margin: 0 auto; /* 强制水平居中 */
    display: flex;
    flex-direction: column;
    align-items: center;
}

h1 { font-size: clamp(2rem, 5vw, 4rem); margin-bottom: 20px; line-height: 1.2; }
p { font-size: clamp(1rem, 2vw, 1.2rem); color: var(--text-secondary); margin-bottom: 40px; }

/* 提示词 */
.suggestion-chips { display: flex; gap: 10px; flex-wrap: wrap; justify-content: center; margin-bottom: 30px; }
.chip { 
    background: var(--chip-bg); 
    color: var(--text-primary); 
    border: 1px solid var(--chip-border);
    padding: 10px 18px; 
    border-radius: 50px; 
    cursor: pointer; 
    display: flex; align-items: center; gap: 6px;
    font-size: 0.9rem;
}

/* 按钮 */
.primary-btn {
    background: var(--accent); color: white; border: none; 
    padding: 16px 40px; border-radius: 50px; font-size: 1.1rem; 
    cursor: pointer; display: inline-flex; align-items: center; gap: 8px;
    box-shadow: 0 4px 15px rgba(0,0,0,0.2);
}

.toast { margin-top: 20px; color: var(--accent); opacity: 0; transition: opacity 0.3s; height: 20px; }
.toast.show { opacity: 1; }

/* 智能体定位修复 */
df-messenger {
    z-index: 9999;
    position: fixed !important; /* 强制 Fixed */
    bottom: 24px !important;    /* 强制底部距离 */
    right: 24px !important;     /* 强制右侧距离 */
    left: auto !important;      /* 防止左侧定位干扰 */
    pointer-events: auto;       /* 允许点击 */
    
    --df-messenger-chat-background: var(--surface);
    --df-messenger-message-user-background: var(--accent);
    --df-messenger-message-user-font-color: #ffffff;
}

/* 动画 */
.fade-in { opacity: 0; animation: fadeInUp 0.8s forwards; transform: translateY(20px); }
.delay-1 { animation-delay: 0.1s; } .delay-2 { animation-delay: 0.2s; } .delay-3 { animation-delay: 0.3s; }
@keyframes fadeInUp { to { opacity: 1; transform: translateY(0); } }