/* ===== CSS Variables ===== */
:root {
    /* Colors matching the app */
    --bg-primary: #0f172a;      /* slate-900 */
    --bg-secondary: #1e293b;    /* slate-800 */
    --bg-tertiary: #334155;     /* slate-700 */
    --bg-quaternary: #475569;   /* slate-600 */
    
    --color-primary: #22d3ee;   /* cyan-400 */
    --color-primary-hover: #06b6d4; /* cyan-500 */
    --color-accent: #fde047;    /* yellow-300 */
    --color-accent-hover: #facc15; /* yellow-400 */
    
    --text-primary: #ffffff;
    --text-secondary: #e2e8f0;  /* slate-200 */
    --text-tertiary: #94a3b8;   /* slate-400 */
    --text-quaternary: #64748b; /* slate-500 */
    
    --success: #22c55e;         /* green-500 */
    --error: #ef4444;           /* red-500 */
    
    /* Spacing */
    --spacing-xs: 0.5rem;
    --spacing-sm: 1rem;
    --spacing-md: 1.5rem;
    --spacing-lg: 2rem;
    --spacing-xl: 3rem;
    --spacing-2xl: 4rem;
    --spacing-3xl: 6rem;
    
    /* Typography */
    --font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, sans-serif;
    --font-size-xs: 0.75rem;
    --font-size-sm: 0.875rem;
    --font-size-base: 1rem;
    --font-size-lg: 1.125rem;
    --font-size-xl: 1.25rem;
    --font-size-2xl: 1.5rem;
    --font-size-3xl: 1.875rem;
    --font-size-4xl: 2.25rem;
    --font-size-5xl: 3rem;
    
    /* Shadows */
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
    --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.1), 0 10px 10px -5px rgba(0, 0, 0, 0.04);
    
    /* Borders */
    --border-radius-sm: 0.375rem;
    --border-radius-md: 0.5rem;
    --border-radius-lg: 0.75rem;
    --border-radius-xl: 1rem;
    --border-radius-2xl: 1.5rem;
    
    /* Transitions */
    --transition-fast: 0.15s ease-in-out;
    --transition-normal: 0.3s ease-in-out;
    --transition-slow: 0.5s ease-in-out;
}

/* ===== Reset & Base Styles ===== */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html {
    font-size: 16px;
    line-height: 1.6;
    scroll-behavior: smooth;
}

body {
    font-family: var(--font-family);
    background-color: var(--bg-primary);
    color: var(--text-primary);
    line-height: 1.6;
    overflow-x: hidden;
}

/* ===== Utility Classes ===== */
.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 var(--spacing-md);
}

.section-title {
    font-size: var(--font-size-4xl);
    font-weight: 700;
    color: var(--color-primary);
    text-align: center;
    margin-bottom: var(--spacing-md);
    line-height: 1.2;
}

.section-subtitle {
    font-size: var(--font-size-lg);
    color: var(--text-tertiary);
    text-align: center;
    margin-bottom: var(--spacing-2xl);
    max-width: 600px;
    margin-left: auto;
    margin-right: auto;
}

/* ===== Header & Navigation ===== */
.header {
    background-color: rgba(15, 23, 42, 0.95);
    backdrop-filter: blur(10px);
    border-bottom: 1px solid var(--bg-tertiary);
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    z-index: 1000;
    transition: var(--transition-normal);
}

.nav-container {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: var(--spacing-sm) 0;
    max-width: 1200px;
    margin: 0 auto;
    padding-left: var(--spacing-md);
    padding-right: var(--spacing-md);
}

.nav-logo h2 {
    font-size: var(--font-size-xl);
    font-weight: 700;
    color: var(--color-primary);
}

.nav-links {
    display: flex;
    gap: var(--spacing-lg);
    align-items: center;
}

.nav-links a {
    color: var(--text-secondary);
    text-decoration: none;
    font-weight: 500;
    transition: var(--transition-fast);
    padding: var(--spacing-xs) var(--spacing-sm);
    border-radius: var(--border-radius-md);
}

.nav-links a:hover {
    color: var(--color-primary);
    background-color: rgba(34, 211, 238, 0.1);
}

.nav-mobile-toggle {
    display: none;
    flex-direction: column;
    cursor: pointer;
    gap: 4px;
}

.nav-mobile-toggle span {
    width: 25px;
    height: 3px;
    background-color: var(--color-primary);
    transition: var(--transition-fast);
}

/* ===== Hero Section ===== */
.hero {
    padding: var(--spacing-2xl) 0; /* 收紧顶部 Hero 区域上下留白 */
    background: linear-gradient(135deg, var(--bg-primary) 0%, var(--bg-secondary) 100%);
    text-align: center;
}

.hero-content {
    margin-bottom: var(--spacing-xl); /* 减小与轮播之间的间距 */
}

/* ===== Screenshot Carousel ===== */
.screenshot-carousel {
    width: 320px;
    max-width: 100%;
    margin: 0 auto;
    position: relative;
}

.carousel-container {
    position: relative;
    width: 100%;
    aspect-ratio: 9 / 19.5; /* iPhone 屏幕纵横比，更贴合截图 */
    background-color: var(--bg-tertiary);
    border-radius: 34px; /* 灵动岛机型更圆的屏幕角 */
    box-shadow: var(--shadow-xl);
    overflow: hidden; /* 裁剪内容以贴合屏幕边缘 */
}

.screenshot-slide {
    position: absolute;
    inset: 0;
    opacity: 0;
    transition: opacity 0.6s ease-in-out;
}

.screenshot-slide.active {
    opacity: 1;
}

.screenshot {
    width: 100%;
    height: 100%;
    object-fit: cover; /* 充满屏幕，避免左右留白 */
    display: block;
}

/* iPhone 刘海与边框模拟 */
.carousel-container::before {
    content: '';
    position: absolute;
    top: 10px; /* 与顶边留空，模拟灵动岛悬浮 */
    left: 50%;
    transform: translateX(-50%);
    width: 36%;
    height: 32px;
    background: #000; /* 硬件遮挡 */
    border-radius: 18px; /* 药丸形 */
    box-shadow: 0 4px 12px rgba(0,0,0,0.45);
    z-index: 2;
}
.carousel-container::after {
    content: '';
    position: absolute;
    inset: 0;
    border-radius: 34px;
    box-shadow: 0 0 0 9px rgba(0,0,0,0.6) inset, 0 10px 30px rgba(0,0,0,0.35); /* 细金属边框与外部阴影 */
    pointer-events: none;
}

.carousel-nav {
    display: flex;
    justify-content: center;
    gap: var(--spacing-sm);
    margin-top: var(--spacing-md);
}

.nav-btn {
    width: 12px;
    height: 12px;
    border-radius: 50%;
    border: none;
    background-color: var(--bg-tertiary);
    cursor: pointer;
    transition: var(--transition-fast);
}

.nav-btn.active,
.nav-btn:hover {
    background-color: var(--color-primary);
}

.hero-title {
    font-size: var(--font-size-5xl);
    font-weight: 800;
    line-height: 1.1;
    margin-bottom: var(--spacing-md);
}

.hero-accent {
    color: var(--color-accent);
    display: block;
}

.hero-subtitle {
    font-size: var(--font-size-xl);
    color: var(--text-secondary);
    margin-bottom: var(--spacing-xl);
    line-height: 1.6;
}

.hero-buttons {
    display: flex;
    gap: var(--spacing-md);
    margin-bottom: var(--spacing-xl);
    flex-wrap: wrap;
}

.btn-primary, .btn-secondary {
    display: inline-flex;
    align-items: center;
    padding: var(--spacing-md) var(--spacing-lg);
    border-radius: var(--border-radius-xl);
    font-weight: 600;
    text-decoration: none;
    transition: var(--transition-normal);
    font-size: var(--font-size-lg);
    border: 2px solid transparent;
}

.btn-primary {
    background: linear-gradient(135deg, var(--color-primary), var(--color-primary-hover));
    color: var(--bg-primary);
    box-shadow: var(--shadow-lg);
}

.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-xl);
}

.btn-secondary {
    background-color: transparent;
    color: var(--text-secondary);
    border-color: var(--bg-tertiary);
}

.btn-secondary:hover {
    background-color: var(--bg-secondary);
    border-color: var(--color-primary);
    color: var(--color-primary);
}

.hero-stats {
    display: flex;
    gap: var(--spacing-xl);
}

.stat {
    text-align: center;
}

.stat-number {
    display: block;
    font-size: var(--font-size-2xl);
    font-weight: 700;
    color: var(--color-primary);
}

.stat-label {
    display: block;
    font-size: var(--font-size-sm);
    color: var(--text-tertiary);
    margin-top: var(--spacing-xs);
}

/* ===== Phone Mockup ===== */
.hero-visual {
    display: flex;
    justify-content: center;
    align-items: center;
}

.phone-mockup {
    width: 300px;
    height: 600px;
    background: linear-gradient(145deg, #2d3748, #1a202c);
    border-radius: 30px;
    padding: 20px;
    box-shadow: var(--shadow-xl);
    position: relative;
}

.phone-mockup::before {
    content: '';
    position: absolute;
    top: 10px;
    left: 50%;
    transform: translateX(-50%);
    width: 60px;
    height: 6px;
    background-color: #4a5568;
    border-radius: 3px;
}

.phone-screen {
    width: 100%;
    height: 100%;
    background-color: var(--bg-primary);
    border-radius: 20px;
    overflow: hidden;
    border: 2px solid var(--bg-tertiary);
}

.app-preview {
    padding: var(--spacing-lg);
    height: 100%;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
}

.app-header {
    text-align: center;
    margin-bottom: var(--spacing-xl);
}

.app-header h3 {
    font-size: var(--font-size-lg);
    color: var(--color-primary);
    margin-bottom: var(--spacing-xs);
}

.app-header p {
    font-size: var(--font-size-sm);
    color: var(--text-tertiary);
}

.number-display {
    background-color: var(--bg-secondary);
    border-radius: var(--border-radius-lg);
    padding: var(--spacing-lg);
    margin-bottom: var(--spacing-lg);
    text-align: center;
    border: 2px solid var(--bg-tertiary);
    width: 100%;
}

.numbers {
    font-size: var(--font-size-2xl);
    font-weight: 700;
    color: var(--color-accent);
    font-family: 'SF Mono', 'Monaco', 'Inconsolata', 'Roboto Mono', monospace;
    letter-spacing: 0.5em;
    margin-bottom: var(--spacing-sm);
}

.timer {
    font-size: var(--font-size-base);
    color: var(--text-tertiary);
}

.difficulty-settings {
    display: flex;
    gap: var(--spacing-sm);
    width: 100%;
}

.setting {
    flex: 1;
    background-color: var(--bg-tertiary);
    padding: var(--spacing-sm);
    border-radius: var(--border-radius-md);
    text-align: center;
    font-size: var(--font-size-xs);
    color: var(--text-secondary);
}


/* ===== How It Works Section ===== */
.how-it-works {
    padding: var(--spacing-xl) 0; /* 收紧版块间距 */
    background-color: var(--bg-secondary);
    text-align: center;
}

.steps {
    display: flex;
    justify-content: center;
    gap: var(--spacing-2xl);
    margin-top: var(--spacing-lg);
    flex-wrap: wrap;
}

.step {
    min-width: 150px;
    text-align: center;
}

.step-number {
    width: 50px;
    height: 50px;
    background: var(--color-primary);
    color: var(--bg-primary);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: var(--font-size-lg);
    font-weight: 700;
    margin: 0 auto var(--spacing-sm);
}

.step h3 {
    font-size: var(--font-size-lg);
    font-weight: 600;
    color: var(--color-primary);
    margin-bottom: var(--spacing-xs);
}

.step p {
    color: var(--text-tertiary);
    font-size: var(--font-size-sm);
}


/* ===== Download Section ===== */
.download {
    padding: var(--spacing-xl) 0; /* 收紧下载区 */
    background-color: var(--bg-primary);
    text-align: center;
}

.download h2 {
    font-size: var(--font-size-3xl);
    font-weight: 700;
    color: var(--color-primary);
    margin-bottom: var(--spacing-lg);
}

.app-store-btn img {
    height: 60px;
    transition: var(--transition-fast);
}

.app-store-btn:hover img {
    transform: scale(1.05);
}

.download-info {
    margin-top: var(--spacing-lg);
    color: var(--text-tertiary);
    font-size: var(--font-size-sm);
}

.info-icon {
    font-size: var(--font-size-base);
}

/* ===== Footer ===== */
.footer {
    background-color: var(--bg-secondary);
    padding: var(--spacing-lg) 0;
    border-top: 1px solid var(--bg-tertiary);
    text-align: center;
}

.footer-links {
    display: flex;
    justify-content: center;
    gap: var(--spacing-lg);
    margin-bottom: var(--spacing-md);
    flex-wrap: wrap;
}

.footer-links a {
    color: var(--text-tertiary);
    text-decoration: none;
    transition: var(--transition-fast);
}

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

.footer p {
    color: var(--text-tertiary);
    font-size: var(--font-size-sm);
}

/* ===== Animations ===== */
@keyframes fadeInUp {
    from {
        opacity: 0;
        transform: translateY(20px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

/* ===== Responsive Design ===== */
@media (max-width: 1024px) {
    .screenshot-carousel {
        width: 300px;
    }
    
    .steps {
        gap: var(--spacing-lg);
    }
}

@media (max-width: 768px) {
    .nav-links {
        display: none;
    }
    
    .hero-title {
        font-size: var(--font-size-3xl);
    }
    
    .hero-subtitle {
        font-size: var(--font-size-base);
    }
    
    .screenshot-carousel { width: 280px; }
    
    .section-title {
        font-size: var(--font-size-2xl);
    }
    
    .steps {
        gap: var(--spacing-lg);
        flex-direction: column;
        align-items: center;
    }
    
    .step {
        max-width: 200px;
    }
    
    .footer-links {
        flex-direction: column;
        gap: var(--spacing-md);
    }
}

@media (max-width: 480px) {
    .container { padding: 0 var(--spacing-sm); }
    .hero-title { font-size: var(--font-size-2xl); }
    .screenshot-carousel { width: 260px; }
    
    .step-number {
        width: 40px;
        height: 40px;
        font-size: var(--font-size-base);
    }
    
    .step h3 {
        font-size: var(--font-size-base);
    }
    
    .step p {
        font-size: var(--font-size-xs);
    }
}

/* ===== Print Styles ===== */
@media print {
    .header,
    .download,
    .footer {
        display: none;
    }
    
    body {
        background-color: white;
        color: black;
    }
    
    .hero,
    .how-it-works {
        background-color: white;
        color: black;
    }
}