/* =============================
   SKY BRAND COLORS
   S = #00c4ff (Cyan Blue)
   K = #ff005e (Pinkish Red)
   Y = #00ffb3 (Neon Green)
   ============================= */
:root {
    --sky-s: #00c4ff;
    --sky-k: #ff005e;
    --sky-y: #00ffb3;
    --text-dark: #1e1e1e;
    --text-light: #555;
    --bg-light: #ffffff;
    --bg-gray: #f5f7fa;
    --border-color: #e6e6e6;
}

/* GLOBAL RESET */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: "Inter", "Poppins", sans-serif;
}
body {
    background: var(--bg-light);
    color: var(--text-dark);
    line-height: 1.6;
    font-size: 17px;
}

.page-wrapper {
    width: 90%;
    max-width: 1000px;
    margin: auto;
    padding-top: 20px;
}

/* BREADCRUMB */
.breadcrumb {
    font-size: 14px;
    margin-bottom: 20px;
    color: var(--text-light);
}
.breadcrumb a {
    color: var(--sky-s);
    text-decoration: none;
}
.breadcrumb span {
    color: var(--text-dark);
}

/* HERO SECTION */
.book-hero {
    display: flex;
    gap: 25px;
    background: var(--bg-gray);
    padding: 20px;
    border-radius: 12px;
    border: 1px solid var(--border-color);
}
.book-cover {
    width: 200px;
    border-radius: 10px;
    box-shadow: 0 4px 12px rgba(0,0,0,0.1);
}
.book-title {
    font-size: 30px;
    font-weight: 700;
    color: var(--sky-k);
    margin-bottom: 5px;
}
.book-author {
    font-size: 16px;
    color: var(--text-light);
    margin-bottom: 15px;
}
.book-intro {
    font-size: 17px;
    color: var(--text-dark);
}

/* SECTION TITLES */
.section-title {
    margin: 40px 0 15px;
    font-size: 26px;
    font-weight: 700;
    color: var(--sky-k);
    border-left: 6px solid var(--sky-y);
    padding-left: 10px;
}


/* VIDEO SECTION */
.video-frame {
    position: relative;
    width: 100%;
    padding-bottom: 56.25%; /* 16:9 ratio */
    height: 0;
    overflow: hidden;
    border-radius: 12px;
    border: 2px solid var(--sky-s);
}

.video-frame iframe {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    border: 0;
}




/* BUY BUTTONS */
.buy-section {
    text-align: center;
    margin-top: 30px;
}
.buy-buttons {
    display: flex;
    gap: 15px;
    justify-content: center;
}
.buy-btn {
    background: var(--sky-s);
    padding: 12px 22px;
    color: #fff;
    text-decoration: none;
    border-radius: 8px;
    font-weight: 600;
    transition: 0.3s;
}
.buy-btn:hover {
    background: var(--sky-k);
}

/* SUMMARY CONTENT */
.summary-content h2 {
    margin-top: 35px;
    font-size: 26px;
    color: var(--sky-k);
}
.summary-content h3 {
    margin-top: 20px;
    font-size: 20px;
    color: var(--sky-s);
}
.summary-content p {
    margin-top: 8px;
    color: var(--text-dark);
}
blockquote {
    border-left: 4px solid var(--sky-y);
    margin: 15px 0;
    padding-left: 15px;
    font-style: italic;
    color: var(--text-light);
}

/* RELATED BOOKS */
.related-section {
    margin-top: 40px;
    padding: 20px;
    background: var(--bg-gray);
    border-radius: 12px;
    border: 1px solid var(--border-color);
}
.related-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 15px;
    margin-top: 15px;
}
.related-grid a {
    background: var(--sky-y);
    padding: 12px;
    display: block;
    text-align: center;
    color: #000;
    font-weight: 600;
    border-radius: 10px;
    text-decoration: none;
    transition: 0.3s;
}
.related-grid a:hover {
    background: var(--sky-k);
    color: #fff;
}

/* RESPONSIVE */
@media (max-width: 768px) {
    .book-hero {
        flex-direction: column;
        text-align: center;
    }

    .book-cover {
        margin: auto;
    }

    .buy-buttons {
        flex-direction: column;
    }
}

/* =============================
   RESPONSIVE HEADER + MOBILE MENU
   ============================= */
.mobile-header {
    display: none;
    background: var(--sky-k);
    padding: 15px;
    color: #fff;
}
.mobile-header .brand {
    font-size: 22px;
    font-weight: 700;
}
.mobile-menu-btn {
    float: right;
    font-size: 26px;
    cursor: pointer;
}
.mobile-nav {
    display: none;
    background: #fff;
    padding: 15px;
    border-top: 2px solid var(--sky-s);
}
.mobile-nav a {
    display: block;
    padding: 10px;
    color: var(--text-dark);
    text-decoration: none;
    font-weight: 600;
}
.mobile-nav a:hover {
    color: var(--sky-k);
}

@media(max-width: 768px){
    .mobile-header{display:block;}
    .desktop-header{display:none;}
}

/* =============================
   CATEGORY PAGE CARD GRID
   ============================= */
.category-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 20px;
    margin-top: 30px;
}
.category-card {
    background: #fff;
    border: 1px solid var(--border-color);
    border-radius: 12px;
    padding: 18px;
    text-align: center;
    transition: 0.3s;
    box-shadow: 0 3px 10px rgba(0,0,0,0.05);
}
.category-card:hover {
    border-color: var(--sky-k);
    transform: translateY(-4px);
}
.category-card img{
    width: 120px;
    margin-bottom: 15px;
}
.category-card-title{
    font-size: 20px;
    font-weight: 700;
    color: var(--sky-s);
}

/* =============================
   DARK THEME
   ============================= */
.dark-mode body{
    background: #0f0f0f;
    color: #f5f5f5;
}
.dark-mode .book-hero,
.dark-mode .related-section{
    background: #1a1a1a;
    border-color: #333;
}
.dark-mode .section-title{
    color: var(--sky-y);
    border-left-color: var(--sky-k);
}
.dark-mode .buy-btn{
    background: var(--sky-y);
}
.dark-mode .related-grid a{
    background: var(--sky-s);
    color:#000;
}
.dark-toggle{
    position: fixed;
    right: 15px;
    bottom: 15px;
    background: var(--sky-k);
    padding: 12px 18px;
    border-radius: 50px;
    color: #fff;
    font-weight: 700;
    cursor: pointer;
    box-shadow: 0 4px 10px rgba(0,0,0,0.2);
}

/* =============================
   ANIMATIONS
   ============================= */
.fade-in{
    opacity: 0;
    animation: fadeIn 0.8s forwards ease;
}
@keyframes fadeIn{
    from{opacity:0;transform:translateY(10px);} to{opacity:1;transform:translateY(0);}
}
.slide-up{
    opacity: 0;
    animation: slideUp 0.7s forwards ease;
}
@keyframes slideUp{
    from{opacity:0;transform:translateY(40px);} to{opacity:1;transform:translateY(0);}
}