/* --- 全局变量与重置 --- */
:root {
    --primary-color: #4f46e5;
    --primary-hover-color: #4338ca;
    --secondary-color: #64748b;
    --secondary-hover-color: #475569;
    --text-color: #1e293b;
    --text-color-light: #334155;
    --bg-color: #ffffff;
    --bg-alt-color: #f8fafc;
    --border-color: #e2e8f0;
    --container-width: 1120px;
    --border-radius: 0.75rem;
    --font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif, "Apple Color Emoji", "Segoe UI Emoji", "Segoe UI Symbol";
    --section-padding: 6rem 0;
}

* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

html, body {
    font-family: var(--font-family);
    color: var(--text-color);
    background-color: var(--bg-color);
    line-height: 1.7;
}

.container {
    max-width: var(--container-width);
    margin: 0 auto;
    padding: 0 1.5rem;
}

/* --- 通用组件 --- */
.btn {
    padding: 0.75rem 1.5rem;
    border: none;
    border-radius: var(--border-radius);
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.2s ease-in-out;
    text-decoration: none;
    display: inline-block;
    box-shadow: 0 4px 14px 0 rgba(0, 0, 0, 0.1);
}

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

.btn-primary:hover {
    background-color: var(--primary-hover-color);
    transform: translateY(-2px);
    box-shadow: 0 6px 20px 0 rgba(0, 0, 0, 0.15);
}

.btn-secondary {
    background-color: white;
    color: var(--text-color);
    border: 1px solid var(--border-color);
    box-shadow: none;
}

.btn-secondary:hover {
    background-color: var(--bg-alt-color);
    transform: translateY(-2px);
    box-shadow: 0 4px 14px 0 rgba(0, 0, 0, 0.05);
}

/* --- 导航栏 --- */
.main-header {
    background-color: var(--bg-color);
    border-bottom: 1px solid var(--border-color);
    position: sticky;
    top: 0;
    z-index: 1000;
}

.main-nav {
    display: flex;
    justify-content: space-between;
    align-items: center;
    height: 70px;
    padding: 0 1.5rem;
    max-width: var(--container-width);
    margin: 0 auto;
}

.logo img {
    height: 30px;
    display: block;
}

.nav-links {
    display: flex;
    list-style: none;
    gap: 2rem;
}

.nav-links a {
    text-decoration: none;
    color: var(--secondary-color);
    font-weight: 500;
    transition: color 0.2s;
}

.nav-links a:hover,
.nav-links a.active {
    color: var(--text-color);
}

.nav-auth {
    display: flex;
    align-items: center;
    gap: 20px;
}

.nav-auth .btn {
    padding: 10px 20px;
    font-size: 14px;
    line-height: 1.5;
}

/* Language Selector Styles */
.language-selector {
    position: relative;
    font-size: 14px;
}

.current-language {
    color: var(--text-color);
    text-decoration: none;
    padding: 10px 20px;
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    display: flex;
    align-items: center;
    gap: 6px;
    transition: background-color 0.3s, color 0.3s;
    line-height: 1.5;
}

.current-language::after {
    content: '▼';
    font-size: 10px;
    display: inline-block;
    transition: transform 0.3s;
}

.language-selector:hover .current-language {
    background-color: var(--light-gray);
    color: var(--dark-blue);
}

.language-selector:hover .current-language::after {
    transform: rotate(180deg);
}

.language-dropdown {
    display: none;
    position: absolute;
    top: 100%;
    right: 0;
    background-color: #fff;
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    box-shadow: 0 4px 12px rgba(0,0,0,0.1);
    list-style: none;
    padding: 5px 0;
    margin: 2px 0 0;
    min-width: 160px;
    z-index: 1000;
    overflow: hidden;
}

.language-selector:hover .language-dropdown {
    display: block;
}

.language-dropdown li a {
    display: block;
    padding: 10px 20px;
    color: var(--text-color);
    text-decoration: none;
    font-size: 14px;
    transition: background-color 0.2s;
}

.language-dropdown li a:hover {
    background-color: var(--light-gray);
    color: var(--dark-blue);
}

/* --- Hero Section --- */
.hero-section {
    background-color: #0c0a1d; /* A deep, dark blue for the space-like feel */
    color: #ffffff;
    padding: 120px 0;
    text-align: center;
    position: relative;
    overflow: hidden; /* Hide anything that spills out */
}

.hero-section .container {
    position: relative;
    z-index: 10; /* Ensure content is above the canvas */
}

#hero-canvas {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    z-index: 2; /* Paper.js canvas behind content */
    pointer-events: none; /* Make it non-interactive */
}

/* Three.js canvas will be injected by JS with z-index: 1 */

.hero-section h1 {
    font-size: 3.5rem;
    line-height: 1.2;
    margin-bottom: 1.5rem;
    color: white;
}

.hero-section .subtitle {
    font-size: 1.25rem;
    color: #9ca3af;
    max-width: 700px;
    margin: 0 auto 2.5rem;
}

.hero-buttons {
    display: flex;
    justify-content: center;
    gap: 1rem;
}

.btn-large {
    padding: 1rem 2rem;
    font-size: 1.1rem;
}

.text-small {
    font-size: 0.9rem;
    color: var(--secondary-color);
}

.mt-2 {
    margin-top: 1rem;
}

/* --- 通用 Section 样式 --- */
.testimonials-section, .features-section-detailed, .how-it-works-section, .faq-section {
    padding: var(--section-padding);
}

.features-section-detailed, .faq-section {
    background-color: var(--bg-alt-color);
}

.text-center {
    text-align: center;
}

.section-title {
    font-size: 2.8rem;
    text-align: center;
    margin-bottom: 1.5rem;
    color: var(--text-color);
    line-height: 1.3;
}

.section-subtitle {
    font-size: 1.2rem;
    color: var(--text-color-light);
    max-width: 700px;
    margin: 0 auto 4.5rem;
    text-align: center;
}

/* --- Testimonials Section --- */
.testimonials-grid {
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    gap: 2rem;
}

.testimonial-card {
    background-color: var(--bg-color);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    padding: 2rem;
    display: flex;
    flex-direction: column;
    justify-content: space-between;
    box-shadow: 0 4px 25px rgba(0,0,0,0.03);
    transition: all 0.3s ease;
    flex: 1 1 300px;
    max-width: 350px;
}

.testimonial-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 10px 30px rgba(0,0,0,0.07);
}

.testimonial-card p {
    font-size: 1.05rem;
    margin-bottom: 1.5rem;
    flex-grow: 1;
}

.testimonial-author {
    display: flex;
    align-items: center;
    gap: 1rem;
}

.testimonial-author img {
    width: 40px;
    height: 40px;
    border-radius: 50%;
}

.testimonial-author span {
    font-size: 0.9rem;
    color: var(--secondary-color);
}

.testimonial-author span strong {
    color: var(--text-color);
    display: block;
}

/* --- Detailed Features Section --- */
.features-grid-detailed {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 2.5rem;
    text-align: left;
}

.feature-item-detailed {
    background-color: transparent;
    padding: 2rem;
    border-radius: var(--border-radius);
    border: 1px solid transparent;
    transition: all 0.3s ease;
}

.feature-item-detailed:hover {
    transform: translateY(-5px);
    background-color: var(--bg-color);
    border-color: var(--border-color);
    box-shadow: 0 10px 30px rgba(0,0,0,0.07);
}

.feature-icon-detailed {
    font-size: 2rem;
    color: var(--primary-color);
    margin-bottom: 1rem;
    display: inline-block;
    width: 60px;
    height: 60px;
    line-height: 60px;
    text-align: center;
    border-radius: 50%;
    background-color: #eef2ff;
}

.feature-item-detailed h3 {
    font-size: 1.3rem;
    margin-bottom: 0.5rem;
}

.feature-item-detailed p {
    color: var(--secondary-color);
}

/* --- How It Works Section --- */
.how-it-works-section {
    background-color: var(--bg-alt-color);
}

.how-it-works-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 1.5rem;
    text-align: center;
    margin-top: 4rem;
    position: relative;
}

.how-it-works-grid::before {
    content: '';
    position: absolute;
    top: 25px;
    left: 16.66%;
    right: 16.66%;
    height: 2px;
    background-image: linear-gradient(to right, #cbd5e1 50%, transparent 50%);
    background-size: 16px 2px;
    background-repeat: repeat-x;
    z-index: -1;
}

.how-it-works-step {
    position: relative;
    background-color: var(--bg-color);
    padding: 2rem;
    border-radius: var(--border-radius);
    border: 1px solid var(--border-color);
    box-shadow: 0 4px 25px rgba(0,0,0,0.03);
}

.how-it-works-step .step-number {
    width: 50px;
    height: 50px;
    border-radius: 50%;
    background-color: #eef2ff;
    color: var(--primary-color);
    font-size: 1.5rem;
    font-weight: 700;
    display: flex;
    justify-content: center;
    align-items: center;
    margin: 0 auto 1.5rem;
    border: 2px solid var(--primary-color);
    background-color: var(--bg-color);
}

.how-it-works-step h3 {
    font-size: 1.3rem;
    margin-bottom: 0.5rem;
}

/* --- FAQ Section --- */
.faq-accordion {
    max-width: 750px;
    margin: 0 auto;
}

.faq-item {
    border-bottom: 1px solid var(--border-color);
}

.faq-item:first-child {
    border-top: 1px solid var(--border-color);
}

.faq-question {
    width: 100%;
    text-align: left;
    padding: 1.75rem 1rem;
    font-size: 1.15rem;
    font-weight: 600;
    background: none;
    border: none;
    cursor: pointer;
    display: flex;
    justify-content: space-between;
    align-items: center;
    transition: color 0.2s ease;
}

.faq-question span {
    padding-right: 1rem;
}

.faq-question:hover {
    color: var(--primary-color);
}

.faq-icon {
    font-size: 1rem;
    color: var(--primary-color);
    transition: transform 0.3s ease-in-out;
}

.faq-item.active .faq-question {
    color: var(--primary-color);
}

.faq-answer {
    max-height: 0;
    overflow: hidden;
    transition: max-height 0.3s ease-in-out;
}

.faq-answer p {
    padding: 0 1rem 1.75rem;
    color: var(--text-color-light);
}

/* --- Detailed Footer --- */
.main-footer-detailed {
    background-color: #111827;
    color: #9ca3af;
    padding: 5rem 0 3rem;
    margin-top: var(--section-padding);
}

.footer-content {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 3rem;
    margin-bottom: 4rem;
}

.footer-column h4 {
    color: white;
    font-size: 1.1rem;
    margin-bottom: 1rem;
}

.footer-column p,
.footer-column li {
    margin-bottom: 0.75rem;
}

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

.footer-column a {
    color: #9ca3af;
    text-decoration: none;
    transition: color 0.2s;
}

.footer-column a:hover {
    color: white;
}

.footer-bottom {
    text-align: center;
    border-top: 1px solid #374151;
    padding-top: 3rem;
    font-size: 0.9rem;
}

/* --- 页脚 --- */
.main-footer {
    background-color: var(--text-color);
    color: #a0aec0;
    text-align: center;
    padding: 2rem 0;
    margin-top: 4rem;
}

/* --- 响应式设计 --- */
@media (max-width: 768px) {
    .nav-links, .nav-auth {
        display: none;
    }

    .hero-section h1 {
        font-size: 2.8rem;
    }
    
    .how-it-works-grid {
        grid-template-columns: 1fr;
        gap: 2rem;
    }
    .how-it-works-grid::before {
        display: none;
    }
}