:root {
    --primary-color: #1a2a44; /* Deep Navy */
    --secondary-color: #c5a059; /* Gold */
    --text-color: #333;
    --paper-color: #fcfaf5;
    --shadow-color: rgba(0, 0, 0, 0.2);
    --transition-speed: 0.8s;
}

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

body {
    background: url("../images/bg.jpg");
    background-size: cover;
    background-position: center;
    background-repeat: no-repeat;
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    font-family: 'Inter', system-ui, -apple-system, sans-serif;
    overflow: hidden;
}

/* Book Container */
.book-wrapper {
    perspective: 2000px;
    display: flex;
    align-items: center;
    justify-content: center;
    width: 100%;
    height: 100%;
}

.book {
    position: relative;
    width: 450px;
    height: 600px;
    transition: transform var(--transition-speed);
    transform-style: preserve-3d;
}

/* Base Page Styles */
.page {
    position: absolute;
    width: 100%;
    height: 100%;
    top: 0;
    left: 0;
    background: var(--paper-color);
    transform-origin: left;
    transform-style: preserve-3d;
    transition: transform var(--transition-speed);
    box-shadow: inset 3px 0 10px var(--shadow-color);
    cursor: pointer;
    user-select: none;
}

.page.flipped {
    transform: rotateY(-180deg);
}

.front, .back {
    position: absolute;
    width: 100%;
    height: 100%;
    top: 0;
    left: 0;
    backface-visibility: hidden;
    padding: 40px;
    display: flex;
    flex-direction: column;
    overflow: hidden;
}

.back {
    transform: rotateY(180deg);
}

/* Paper Texture Effect */
.front::before, .back::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: url('https://www.transparenttextures.com/patterns/paper-fibers.png');
    opacity: 0.1;
    pointer-events: none;
}

/* Cover Styling */
.cover-front {
    background: var(--primary-color);
    color: white;
    justify-content: space-between;
    align-items: center;
    text-align: center;
    border-radius: 5px 15px 15px 5px;
}

.cover-front h1 {
    font-size: 2.2rem;
    margin-top: 20px;
    color: var(--secondary-color);
    text-transform: uppercase;
    letter-spacing: 2px;
}

.cover-front .org {
    font-size: 0.9rem;
    font-weight: 300;
    opacity: 0.8;
}

.cover-image {
    width: 80%;
    height: 250px;
    background-size: cover;
    background-position: center;
    border: 2px solid var(--secondary-color);
    margin: 20px 0;
    box-shadow: 0 10px 20px rgba(0,0,0,0.5);
}

/* Interior Pages Styling */
.page-header {
    border-bottom: 2px solid var(--secondary-color);
    padding-bottom: 10px;
    margin-bottom: 20px;
}

.page-header h2 {
    font-size: 1.2rem;
    color: var(--primary-color);
}

.content {
    font-size: 0.95rem;
    line-height: 1.6;
    color: #444;
}

.content h3 {
    font-size: 1.1rem;
    margin: 15px 0 10px;
    color: var(--primary-color);
}

.content p {
    margin-bottom: 15px;
    text-align: justify;
}

.content ul {
    margin-bottom: 15px;
    padding-left: 20px;
}

.content li {
    margin-bottom: 5px;
}

.page-footer {
    margin-top: auto;
    font-size: 0.75rem;
    color: #888;
    display: flex;
    justify-content: space-between;
    border-top: 1px solid #eee;
    padding-top: 10px;
}

/* Navigation Buttons */
.nav-buttons {
    position: fixed;
    bottom: 30px;
    display: flex;
    gap: 20px;
    z-index: 100;
}

.btn {
    background: rgba(255, 255, 255, 0.1);
    backdrop-filter: blur(5px);
    border: 1px solid var(--secondary-color);
    color: var(--secondary-color);
    padding: 10px 25px;
    border-radius: 30px;
    cursor: pointer;
    transition: 0.3s;
    font-weight: 600;
    text-transform: uppercase;
    font-size: 0.8rem;
    outline: none;
}

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

/* Responsive */
@media (max-width: 500px) {
    .book {
        width: 320px;
        height: 480px;
    }
    .front, .back {
        padding: 20px;
    }
}

.logo-top-left {
    position: absolute;
    top: 15px;
    left: 15px;

    display: flex;
    gap: 10px;
    align-items: center;

    /* 🔥 BACKGROUND PUTIH */
    background: white;

    /* padding biar logo tidak nempel */
    padding: 8px 12px;

    /* 🔥 radius hanya kanan */
    border-radius: 0 18px 18px 0;

    /* biar terlihat premium */
    box-shadow: 0 6px 15px rgba(0,0,0,0.25);

    z-index: 10;
}

.logo-top-left img {
    height: 20px;
    filter: drop-shadow(0 2px 4px rgba(0,0,0,0.4));
}

.cover-front {
    box-shadow: none !important;
    border: none !important;
}