:root[data-theme="dark"] {
    --bg-image: url('./assets/aurora_dark.png');
    --text-primary: #ffffff;
    --text-secondary: #cbd5e1;
    --glass-bg: rgba(15, 23, 42, 0.4);
    --glass-border: rgba(255, 255, 255, 0.1);
    --glass-shadow: rgba(0, 0, 0, 0.3);
    --accent: #2dd4bf; /* Teal/Cyan */
    --accent-hover: #14b8a6;
    --card-bg-hover: rgba(30, 41, 59, 0.6);
}

:root[data-theme="light"] {
    --bg-image: url('./assets/aurora_light.png');
    --text-primary: #1e293b;
    --text-secondary: #334155;
    --glass-bg: rgba(255, 255, 255, 0.5);
    --glass-border: rgba(255, 255, 255, 0.6);
    --glass-shadow: rgba(100, 116, 133, 0.15);
    --accent: #0284c7; /* Ocean Blue */
    --accent-hover: #0369a1;
    --card-bg-hover: rgba(255, 255, 255, 0.8);
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: 'Outfit', sans-serif;
    transition: background-color 0.3s ease, color 0.3s ease, border-color 0.3s ease;
}

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

.background-container {
    position: fixed;
    top: 0;
    left: 0;
    width: 100vw;
    height: 100vh;
    z-index: -1;
    background-image: var(--bg-image);
    background-size: cover;
    background-position: center;
    background-attachment: fixed;
    transition: background-image 0.8s ease-in-out;
}

/* Glassmorphism Utilities */
.glass-header {
    background: var(--glass-bg);
    backdrop-filter: blur(16px);
    -webkit-backdrop-filter: blur(16px);
    border-bottom: 1px solid var(--glass-border);
    box-shadow: 0 4px 30px var(--glass-shadow);
}

.glass-panel {
    background: var(--glass-bg);
    backdrop-filter: blur(16px);
    -webkit-backdrop-filter: blur(16px);
    border: 1px solid var(--glass-border);
    box-shadow: 0 8px 32px 0 var(--glass-shadow);
}

.glass-footer {
    background: var(--glass-bg);
    backdrop-filter: blur(16px);
    -webkit-backdrop-filter: blur(16px);
    border-top: 1px solid var(--glass-border);
}

/* Header */
header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 1.5rem 5%;
    position: sticky;
    top: 0;
    z-index: 100;
}

.logo-link {
    display: inline-block;
    height: 75px; /* 將 Logo 稍微縮小 */
    transition: transform 0.3s ease;
}

.logo-link:hover {
    transform: scale(1.05) translateY(-2px);
}

.logo-img {
    height: 100%;
    width: auto;
    object-fit: contain;
}

/* 深色模式：SVG 預設為黑色，使用 invert(1) 轉為白色 */
:root[data-theme="dark"] .logo-img {
    filter: invert(1);
}

/* 淺色模式：SVG 預設為黑色，直接顯示即可 */
:root[data-theme="light"] .logo-img {
    filter: invert(0);
}

.nav-actions {
    display: flex;
    align-items: center;
    gap: 1.5rem;
}

.icon-btn {
    background: transparent;
    border: none;
    color: var(--text-primary);
    font-size: 1.25rem;
    cursor: pointer;
    padding: 0.5rem;
    border-radius: 50%;
    transition: transform 0.2s;
}

.icon-btn:hover {
    transform: scale(1.1);
}

.cta-btn {
    text-decoration: none;
    color: #fff;
    background: var(--accent);
    padding: 0.6rem 1.4rem;
    border-radius: 20px;
    font-weight: 600;
    font-size: 0.95rem;
    transition: background 0.3s, transform 0.2s;
}

.cta-btn:hover {
    background: var(--accent-hover);
    transform: translateY(-2px);
}

/* Main Content */
main {
    flex: 1;
    display: flex;
    flex-direction: column;
    align-items: center;
    padding: 2rem 5%;
    gap: 4rem;
}

/* Hero Section */
.hero {
    width: 100%;
    max-width: 900px;
    margin-top: 6vh;
}

.hero-content {
    padding: 4.5rem 3rem;
    border-radius: 24px;
    text-align: center;
}

.hero-content h1 {
    font-size: clamp(2.5rem, 5vw, 4rem);
    font-weight: 700;
    margin-bottom: 1.5rem;
    line-height: 1.2;
}

.hero-content p {
    font-size: 1.2rem;
    color: var(--text-secondary);
    margin-bottom: 2.5rem;
    max-width: 700px;
    margin-left: auto;
    margin-right: auto;
    line-height: 1.6;
}

.hero-cta {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 1rem;
}

.btn-primary {
    display: inline-block;
    padding: 1.1rem 2.8rem;
    background: var(--accent);
    color: #fff;
    text-decoration: none;
    font-size: 1.2rem;
    font-weight: 600;
    border-radius: 30px;
    transition: all 0.3s ease;
    box-shadow: 0 4px 15px rgba(0, 0, 0, 0.2);
}

.btn-primary:hover {
    background: var(--accent-hover);
    transform: translateY(-3px) scale(1.02);
    box-shadow: 0 6px 20px rgba(0, 0, 0, 0.25);
}

.subtitle {
    font-size: 0.9rem !important;
    opacity: 0.9;
    margin-bottom: 0 !important;
}

/* Features Section */
.features {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 2.5rem;
    width: 100%;
    max-width: 1200px;
    margin-bottom: 5vh;
}

.feature-card {
    padding: 3rem 2.5rem;
    border-radius: 20px;
    display: flex;
    flex-direction: column;
    align-items: flex-start;
    gap: 1.2rem;
}

.feature-card.interactive {
    transition: transform 0.4s cubic-bezier(0.175, 0.885, 0.32, 1.275), background 0.3s ease, box-shadow 0.3s ease;
}

.feature-card.interactive:hover {
    transform: translateY(-12px);
    background: var(--card-bg-hover);
    box-shadow: 0 20px 40px 0 var(--glass-shadow);
}

.feature-icon {
    font-size: 2.8rem;
    color: var(--accent);
    margin-bottom: 0.5rem;
}

.feature-card h3 {
    font-size: 1.6rem;
    font-weight: 600;
}

.feature-card p {
    color: var(--text-secondary);
    line-height: 1.7;
    font-size: 1.05rem;
}

/* Footer */
footer {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 1.5rem 5%;
    margin-top: auto;
    font-size: 0.9rem;
    color: var(--text-secondary);
}

.footer-links {
    display: flex;
    gap: 1.5rem;
}

.footer-links a {
    color: var(--text-secondary);
    text-decoration: none;
    transition: color 0.2s;
}

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

/* Responsive */
@media (max-width: 768px) {
    header {
        flex-direction: column;
        gap: 1.2rem;
        padding: 1.2rem;
    }
    
    footer {
        flex-direction: column;
        gap: 1rem;
        text-align: center;
    }

    .hero-content {
        padding: 2.5rem 1.5rem;
    }

    .feature-card {
        align-items: center;
        text-align: center;
    }
}