:root {
    --primary-color: #000;
    --paper-color: #ffffff;
    --bg-start: #f5f5f5;
    --bg-end: #8e9ba6;
}

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

body {
    background: radial-gradient(circle, var(--bg-start) 0%, var(--bg-end) 100%);
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    font-family: 'Inter', sans-serif;
    overflow: hidden;
}

.book-wrapper {
    width: 100%;
    height: 100%;
    display: flex;
    justify-content: center;
    align-items: center;
    padding: 20px;
}

#flipbook {
    width: 922px; /* 461 * 2 for double spread */
    height: 600px;
    box-shadow: 0 0 20px rgba(0,0,0,0.4);
}

.page-container {
    background: var(--paper-color);
}

.page-content {
    width: 100%;
    height: 100%;
    padding: 50px;
    display: flex;
    flex-direction: column;
    position: relative;
    background: white;
}

/* Tipografi Steve Jobs Style (Serif) */
.page-content h2 {
    font-family: 'Georgia', serif;
    font-size: 1.8rem;
    color: #333;
    margin-bottom: 25px;
    font-weight: normal;
}

.content {
    font-family: 'Georgia', serif;
    font-size: 1.05rem;
    line-height: 1.6;
    color: #444;
    text-align: justify;
}

/* Spine Shadow (Efek Lipatan di Tengah) */
.flipbook .odd .page-content::after {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 30px;
    height: 100%;
    background: linear-gradient(to right, rgba(0,0,0,0.1) 0%, rgba(0,0,0,0) 100%);
}

.flipbook .even .page-content::after {
    content: '';
    position: absolute;
    top: 0;
    right: 0;
    width: 30px;
    height: 100%;
    background: linear-gradient(to left, rgba(0,0,0,0.1) 0%, rgba(0,0,0,0) 100%);
}

/* Cover Styling */
.cover {
    background-color: #fff !important;
}

.cover h1 {
    font-family: 'Inter', sans-serif;
    font-weight: 700;
    font-size: 2.2rem;
    color: #000;
    letter-spacing: -1px;
    margin-bottom: 20px;
}

.cover .org {
    font-size: 0.9rem;
    text-transform: uppercase;
    color: #666;
    letter-spacing: 2px;
}

.cover-image {
    width: 100%;
    height: 350px;
    background-size: cover;
    background-position: center;
    margin: 20px 0;
    box-shadow: inset 0 0 100px rgba(0,0,0,0.1);
}

/* Page Footer / numbering */
.page-footer {
    position: absolute;
    bottom: 30px;
    left: 50px;
    right: 50px;
    font-size: 0.8rem;
    color: #999;
    font-family: serif;
    display: flex;
    justify-content: space-between;
}

/* Navigation Controls - Steve Jobs Style Minimalist */
.nav-buttons {
    position: fixed;
    bottom: 20px;
    display: flex;
    gap: 10px;
    z-index: 999;
}

.btn {
    background: none;
    border: none;
    color: #666;
    font-size: 0.75rem;
    text-transform: uppercase;
    letter-spacing: 1px;
    cursor: pointer;
    padding: 10px;
    transition: 0.2s;
}

.btn:hover { color: #000; }

/* Responsive */
@media (max-width: 1000px) {
    #flipbook {
        width: 461px !important;
        height: 600px !important;
    }
}