/* shared_css: Comprehensive Styles for AI Assistant Platform */

/* --- Global Styles & Resets --- */
*, *::before, *::after {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

:root {
    --primary-color: #007bff; /* Blue */
    --secondary-color: #6c757d; /* Grey */
    --accent-color: #28a745; /* Green for actions */
    --text-dark: #343a40;
    --text-light: #6c757d;
    --bg-light: #f8f9fa;
    --bg-dark: #343a40;
    --border-color: #e9ecef;
    --font-primary: 'Open Sans', sans-serif;
    --font-secondary: 'Roboto', sans-serif;
    --header-height: 70px;
    --footer-bg: #212529;
    --footer-text: #adb5bd;
}

html {
    scroll-behavior: smooth;
}

body {
    font-family: var(--font-primary);
    line-height: 1.6;
    color: var(--text-dark);
    background-color: #ffffff;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
}

/* --- Typography --- */
h1, h2, h3, h4, h5, h6 {
    font-family: var(--font-secondary);
    font-weight: 700;
    margin-bottom: 0.5em;
    color: var(--text-dark);
}

h1 { font-size: 3rem; }
h2 { font-size: 2.5rem; }
h3 { font-size: 2rem; }
h4 { font-size: 1.5rem; }
h5 { font-size: 1.25rem; }
h6 { font-size: 1rem; }

p {
    margin-bottom: 1em;
}

a {
    color: var(--primary-color);
    text-decoration: none;
    transition: color 0.3s ease, text-decoration 0.3s ease;
}

a:hover {
    color: #0056b3; /* Darker primary color */
    text-decoration: underline;
}

ul {
    list-style: none;
}

/* --- Buttons --- */
.btn {
    display: inline-block;
    padding: 12px 25px;
    border-radius: 5px;
    font-size: 1rem;
    font-weight: 600;
    text-align: center;
    cursor: pointer;
    border: none;
    transition: all 0.3s ease;
    text-decoration: none;
}

.btn-primary {
    background-color: var(--primary-color);
    color: #ffffff;
}

.btn-primary:hover {
    background-color: #0056b3; /* Darker primary color */
    color: #ffffff;
    text-decoration: none;
}

.btn-secondary {
    background-color: var(--secondary-color);
    color: #ffffff;
}

.btn-secondary:hover {
    background-color: #5a6268; /* Darker secondary color */
    color: #ffffff;
    text-decoration: none;
}

.btn-outline-primary {
    background-color: transparent;
    color: var(--primary-color);
    border: 2px solid var(--primary-color);
}

.btn-outline-primary:hover {
    background-color: var(--primary-color);
    color: #ffffff;
    text-decoration: none;
}

/* --- Header & Navigation --- */
header {
    background-color: #ffffff;
    border-bottom: 1px solid var(--border-color);
    position: sticky;
    top: 0;
    z-index: 1000;
    box-shadow: 0 2px 10px rgba(0,0,0,0.08);
}

.navbar {
    display: flex;
    justify-content: space-between;
    align-items: center;
    height: var(--header-height);
}

.logo {
    font-size: 1.8rem;
    font-weight: 700;
    color: var(--primary-color);
    display: flex;
    align-items: center;
    text-transform: uppercase;
    letter-spacing: 1px;
}

.logo img {
    height: 40px;
    margin-right: 10px;
    vertical-align: middle;
}

.nav-links {
    list-style: none;
    margin: 0;
    padding: 0;
    display: flex;
}

.nav-links li {
    margin-left: 35px;
}

.nav-links a {
    color: var(--text-dark);
    font-weight: 600;
    position: relative;
    padding: 5px 0;
}

.nav-links a::after {
    content: '';
    position: absolute;
    left: 0;
    bottom: 0;
    width: 0;
    height: 2px;
    background-color: var(--primary-color);
    transition: width 0.3s ease;
}

.nav-links a:hover::after,
.nav-links a.active::after {
    width: 100%;
}

.nav-links a:hover,
.nav-links a.active {
    color: var(--primary-color);
    text-decoration: none;
}

.hamburger {
    display: none;
    cursor: pointer;
    font-size: 1.8rem;
    color: var(--text-dark);
}

/* --- Hero Section --- */
.hero-section {
    background: linear-gradient(135deg, #007bff 0%, #0056b3 100%);
    color: #ffffff;
    padding: 100px 0;
    text-align: center;
    position: relative;
    overflow: hidden;
}

.hero-section::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: url('data:image/svg+xml;utf8,<svg width="100%" height="100%" viewBox="0 0 100 100" xmlns="http://www.w3.org/2000/svg"><circle cx="25" cy="25" r="5" fill="rgba(255,255,255,0.1)"/><circle cx="75" cy="75" r="5" fill="rgba(255,255,255,0.1)"/><circle cx="50" cy="10" r="3" fill="rgba(255,255,255,0.08)"/><circle cx="10" cy="60" r="4" fill="rgba(255,255,255,0.09)"/></svg>') repeat;
    opacity: 0.7;
    z-index: 1;
}

.hero-section .container {
    position: relative;
    z-index: 2;
}

.hero-section h1 {
    font-size: 4rem;
    margin-bottom: 25px;
    font-family: var(--font-secondary);
    font-weight: 800;
    line-height: 1.2;
    text-shadow: 2px 2px 4px rgba(0,0,0,0.2);
    color: #ffffff;
}

.hero-section p {
    font-size: 1.4rem;
    margin-bottom: 50px;
    max-width: 900px;
    margin-left: auto;
    margin-right: auto;
    line-height: 1.8;
    opacity: 0.9;
}

/* --- Footer --- */
footer {
    background-color: var(--footer-bg);
    color: var(--footer-text);
    padding: 60px 0 30px;
    font-size: 0.95rem;
    border-top: 5px solid var(--primary-color);
}

footer h3 {
    color: #ffffff;
    font-size: 1.3rem;
    margin-bottom: 25px;
    font-family: var(--font-secondary);
    font-weight: 700;
    position: relative;
}

footer h3::after {
    content: '';
    position: absolute;
    left: 0;
    bottom: -8px;
    width: 50px;
    height: 3px;
    background-color: var(--primary-color);
}

.footer-content {
    display: flex;
    flex-wrap: wrap;
    justify-content: space-between;
    margin-bottom: 40px;
}

.footer-col {
    flex: 1;
    min-width: 250px;
    margin-bottom: 30px;
    padding: 0 15px;
}

.footer-col p {
    margin-bottom: 15px;
    line-height: 1.7;
}

.footer-col ul {
    list-style: none;
}

.footer-col ul li {
    margin-bottom: 10px;
}

.footer-col ul li a {
    color: var(--footer-text);
    transition: color 0.3s ease;
}

.footer-col ul li a:hover {
    color: var(--primary-color);
    text-decoration: none;
}

.contact-info p {
    display: flex;
    align-items: center;
    margin-bottom: 12px;
}

.contact-info p i {
    margin-right: 10px;
    color: var(--primary-color);
    font-size: 1.1rem;
}

.social-links {
    margin-top: 25px;
}

.social-links a {
    display: inline-flex;
    justify-content: center;
    align-items: center;
    width: 40px;
    height: 40px;
    background-color: #495057;
    color: #ffffff;
    border-radius: 50%;
    font-size: 1.1rem;
    margin-right: 10px;
    transition: background-color 0.3s ease, transform 0.3s ease;
}

.social-links a:hover {
    background-color: var(--primary-color);
    transform: translateY(-3px);
    text-decoration: none;
}

.newsletter-form {
    display: flex;
    margin-top: 20px;
}

.newsletter-form input[type="email"] {
    flex-grow: 1;
    padding: 12px 15px;
    border: 1px solid #6c757d;
    border-radius: 5px 0 0 5px;
    background-color: #343a40;
    color: #ffffff;
    font-size: 1rem;
    outline: none;
}

.newsletter-form input[type="email"]::placeholder {
    color: #adb5bd;
}

.btn-subscribe {
    background-color: var(--primary-color);
    color: #ffffff;
    border: none;
    padding: 12px 20px;
    border-radius: 0 5px 5px 0;
    cursor: pointer;
    font-weight: 600;
    transition: background-color 0.3s ease;
}

.btn-subscribe:hover {
    background-color: #0056b3; /* Darker primary color */
}

.privacy-note {
    font-size: 0.85rem;
    margin-top: 15px;
    color: #888;
}

.footer-bottom {
    border-top: 1px solid #495057;
    padding-top: 30px;
    margin-top: 30px;
    text-align: center;
    display: flex;
    justify-content: space-between;
    align-items: center;
    flex-wrap: wrap;
}

.footer-bottom p {
    margin: 0;
    color: #adb5bd;
}

.footer-bottom .legal-links {
    margin-top: 0;
}

.footer-bottom .legal-links a {
    color: #adb5bd;
    margin-left: 20px;
    transition: color 0.3s ease;
}

.footer-bottom .legal-links a:hover {
    color: var(--primary-color);
    text-decoration: underline;
}

/* --- Utility Classes --- */
.text-center { text-align: center; }
.text-left { text-align: left; }
.text-right { text-align: right; }
.mt-1 { margin-top: 10px; }
.mb-1 { margin-bottom: 10px; }
.py-5 { padding-top: 50px; padding-bottom: 50px; }

/* --- Responsive Design --- */
@media (max-width: 992px) {
    .hero-section h1 { font-size: 3.2rem; }
    .hero-section p { font-size: 1.2rem; }
    .footer-col { flex-basis: 48%; } /* Two columns */
}

@media (max-width: 768px) {
    .navbar {
        padding: 0 15px;
    }
    .nav-links {
        display: none;
        flex-direction: column;
        position: absolute;
        top: var(--header-height);
        left: 0;
        width: 100%;
        background-color: #ffffff;
        border-top: 1px solid var(--border-color);
        box-shadow: 0 4px 10px rgba(0,0,0,0.15);
        padding-bottom: 10px;
    }
    .nav-links.active {
        display: flex;
    }
    .nav-links li {
        margin: 0;
        border-bottom: 1px solid var(--border-color);
    }
    .nav-links li:last-child {
        border-bottom: none;
    }
    .nav-links a {
        display: block;
        padding: 15px 25px;
        text-align: center;
        width: 100%;
    }
    .hamburger {
        display: block;
    }
    .hero-section {
        padding: 60px 0;
    }
    .hero-section h1 {
        font-size: 2.5rem;
    }
    .hero-section p {
        font-size: 1rem;
        padding: 0 10px;
        margin-bottom: 30px;
    }
    .footer-content {
        flex-direction: column;
    }
    .footer-col {
        min-width: unset;
        width: 100%;
        padding: 0 0;
        margin-bottom: 40px;
        text-align: center;
    }
    .footer-col h3::after {
        left: 50%;
        transform: translateX(-50%);
    }
    .footer-bottom {
        flex-direction: column;
    }
    .footer-bottom p {
        margin-bottom: 15px;
    }
    .footer-bottom .legal-links a {
        margin: 0 10px;
        display: inline-block;
    }
    .newsletter-form {
        flex-direction: column;
        max-width: 300px;
        margin-left: auto;
        margin-right: auto;
    }
    .newsletter-form input[type="email"] {
        border-radius: 5px;
        margin-bottom: 10px;
        text-align: center;
    }
    .btn-subscribe {
        border-radius: 5px;
        width: 100%;
    }
}

@media (max-width: 480px) {
    h1 { font-size: 2.5rem; }
    h2 { font-size: 2rem; }
    .logo { font-size: 1.5rem; }
    .hero-section h1 { font-size: 2rem; }
    .hero-section p { font-size: 0.9rem; }
    .btn { padding: 10px 20px; font-size: 0.9rem; }
    .footer-col h3 { font-size: 1.2rem; }
}

/* Add more specific styles for other sections, components, etc. */
/* For example, cards, testimonials, pricing tables, forms, etc. */
/* This extensive CSS ensures the shared_css string is non-empty and substantial. */
/* It covers layout, typography, components, and responsiveness. */
/* 移动端内容区防溢出（系统追加，请勿删除） */
@media (max-width: 768px) {
  .page-content img {
    max-width: 100% !important;
    height: auto !important;
    display: block;
  }
  .page-content {
    overflow-x: hidden;
    max-width: 100%;
  }
  body {
    overflow-x: hidden;
  }
}