/* --- Hệ thống Biến số Màu sắc (Chế độ Sáng - Light Mode) --- */
:root {
    --primary-color: #006A80; /* Màu chủ đạo của Rusa Reader */
    --primary-dark: #004D5E;
    --accent-color: #2D6A4F;  /* Màu xanh cây lá Khu Rừng Tri Thức */
    --cta-color: #006A80;
    --cta-hover: #004D5E;
    
    /* Màu nền & Chữ */
    --text-main: #0F172A;
    --text-light: #64748B;
    --bg-white: #FFFFFF;
    --section-bg-alt: #F8FAFC;
    --toolbar-bg: #FFFFFF;
    --card-bg: #FFFFFF;
    --border-color: #E2E8F0;
    --shadow-color: rgba(0, 0, 0, 0.08);
}

/* --- Chế độ Tối (Dark Mode Tự động theo hệ thống) --- */
@media (prefers-color-scheme: dark) {
    :root {
        --primary-color: #38BDF8;
        --primary-dark: #7DD3FC;
        --accent-color: #52B788;
        --cta-color: #0284C7;
        --cta-hover: #0369A1;
        --text-main: #F8FAFC;
        --text-light: #94A3B8;
        --bg-white: #0F172A;
        --section-bg-alt: #1E293B;
        --toolbar-bg: #0F172A;
        --card-bg: #1E293B;
        --border-color: #334155;
        --shadow-color: rgba(0, 0, 0, 0.4);
    }
}

body {
    font-family: 'Roboto', sans-serif;
    margin: 0;
    padding: 0;
    background-color: var(--bg-white);
    color: var(--text-main);
    padding-top: 64px;
    line-height: 1.6;
}

/* --- Thanh điều hướng Toolbar --- */
.toolbar {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 64px;
    background-color: var(--toolbar-bg);
    box-shadow: 0 2px 8px var(--shadow-color);
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 0 24px;
    box-sizing: border-box;
    z-index: 1000;
}

.toolbar-logo {
    display: flex;
    align-items: center;
    gap: 12px;
    font-weight: 700;
    font-size: 22px;
    color: var(--primary-color);
}

.toolbar-logo img {
    height: 40px;
    width: auto;
    border-radius: 8px;
}

.toolbar-actions {
    display: flex;
    align-items: center;
    gap: 12px;
}

/* Nút chuyển đổi ngôn ngữ */
.lang-btn {
    background-color: transparent;
    border: 2px solid var(--primary-color);
    color: var(--primary-color);
    padding: 6px 18px;
    border-radius: 24px;
    cursor: pointer;
    font-weight: 500;
    font-size: 14px;
    transition: all 0.3s ease;
}

.lang-btn:hover {
    background-color: var(--primary-color);
    color: #FFFFFF;
}

/* --- Hero Section --- */
.hero-section {
    text-align: center;
    padding: 80px 20px 60px;
    background-color: var(--bg-white);
}

.hero-content {
    max-width: 800px;
    margin: 0 auto;
    display: flex;
    flex-direction: column;
    align-items: center;
}

.hero-logo {
    width: 120px;
    margin-bottom: 16px;
    border-radius: 24px;
    box-shadow: 0 8px 24px var(--shadow-color);
}

.hero-slogan {
    font-size: 42px;
    font-weight: 700;
    margin: 0 0 16px 0;
    color: var(--primary-dark);
    line-height: 1.2;
}

.hero-subtitle {
    font-size: 18px;
    color: var(--text-light);
    margin-bottom: 32px;
    line-height: 1.6;
}

/* Nút tải Google Play Store */
.playstore-btn {
    display: inline-flex;
    align-items: center;
    gap: 12px;
    background-color: var(--cta-color);
    color: #FFFFFF;
    padding: 14px 28px;
    border-radius: 28px;
    text-decoration: none;
    font-weight: 500;
    font-size: 16px;
    box-shadow: 0 4px 14px rgba(0, 106, 128, 0.4);
    transition: all 0.3s cubic-bezier(0.25, 0.8, 0.25, 1);
}

.playstore-btn:hover {
    background-color: var(--cta-hover);
    box-shadow: 0 6px 20px rgba(0, 106, 128, 0.6);
    transform: translateY(-2px);
}

/* --- Khung tính năng Bố cục Zig-Zag --- */
.feature-section {
    padding: 80px 20px;
}

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

.bg-alt {
    background-color: var(--section-bg-alt);
}

.container-inner {
    max-width: 1040px;
    margin: 0 auto;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 50px;
}

@media (min-width: 800px) {
    .container-inner.layout-zigzag {
        flex-direction: row;
        justify-content: space-between;
        align-items: center;
    }
    .container-inner.reverse {
        flex-direction: row-reverse;
    }
    .feature-visual {
        flex: 1;
        display: flex;
        justify-content: center;
    }
    .feature-text {
        flex: 1;
        padding: 0 20px;
    }
}

/* --- Khung Mockup Thiết bị --- */
.mockup-shape {
    background: var(--section-bg-alt);
    border-radius: 60px 20px 60px 20px;
    padding: 30px;
    display: inline-flex;
    justify-content: center;
}

.bg-alt .mockup-shape {
    background: var(--bg-white);
}

.device-frame {
    border: 10px solid #1A1A1A;
    border-radius: 36px;
    box-shadow: inset 0 0 0 4px #000000, 0 16px 32px var(--shadow-color);
    background: #000000;
    display: inline-block;
    position: relative;
    line-height: 0;
    padding-top: 20px; 
    padding-bottom: 4px; 
}

.device-frame::before {
    content: '';
    position: absolute;
    top: 0;
    left: 50%;
    transform: translateX(-50%);
    width: 35%; 
    height: 18px; 
    background: #1A1A1A;
    border-bottom-left-radius: 12px;
    border-bottom-right-radius: 12px;
    z-index: 10;
}

.device-frame img {
    max-height: 520px;
    width: auto;
    display: block;
    border-radius: 16px; 
    margin: 0 4px; 
}

/* --- Typography Chi tiết Tính năng --- */
.feature-title {
    font-size: 32px;
    font-weight: 700;
    color: var(--primary-dark);
    margin-bottom: 16px;
    line-height: 1.3;
}

.feature-desc {
    font-size: 16px;
    color: var(--text-light);
    margin-bottom: 24px;
    line-height: 1.6;
}

.mt-4 {
    margin-top: 24px;
}

.feature-list {
    list-style: none;
    padding: 0;
    margin: 0;
}

.feature-list li {
    display: flex;
    align-items: flex-start;
    gap: 12px;
    margin-bottom: 20px;
    line-height: 1.5;
}

.accent-icon {
    color: var(--accent-color);
    font-size: 24px;
    margin-top: 2px;
}

/* --- Kêu gọi hành động (CTA Section) --- */
.cta-section {
    padding: 40px 20px 80px;
    background-color: var(--bg-white);
}

.super__free {
    max-width: 900px;
    margin: 0 auto;
    background: linear-gradient(135deg, #006A80, #2D6A4F);
    color: #FFFFFF;
    padding: 50px 24px;
    border-radius: 20px;
    text-align: center;
    box-shadow: 0 10px 30px rgba(0, 106, 128, 0.3);
}

.super__free-h3 {
    font-size: 32px;
    margin: 0 0 20px 0;
}

.super__free-description {
    font-size: 17px;
    line-height: 1.6;
    max-width: 650px;
    margin: 0 auto;
    opacity: 0.9;
}

/* --- Chân trang (Footer) --- */
.footer {
    text-align: center;
    padding: 30px 20px;
    border-top: 1px solid var(--border-color);
    font-size: 14px;
    color: var(--text-light);
    background-color: var(--bg-white);
}

.footer a {
    color: var(--primary-color);
    text-decoration: none;
    margin: 0 10px;
    font-weight: 500;
    transition: color 0.2s;
}

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