* {
    box-sizing: border-box;
}

body, html {
    margin: 0;
    padding: 0;
    width: 100%;
    height: 100%;
    background-color: #eae6df;
    overflow: hidden; /* Essential to hide panned canvas boundaries */
    font-family: system-ui, sans-serif;
    display: flex;
    justify-content: center;
    align-items: center;
}

/* Fullscreen Loading Overlay */
#loader-overlay {
    position: fixed;
    top: 0; left: 0; width: 100%; height: 100%;
    z-index: 9999;
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    transition: opacity 0.5s ease;
}

.spinner {
    width: 50px;
    height: 50px;
    border: 3px solid rgba(140, 131, 117, 0.2);
    border-top-color: white;
    border-radius: 50%;
    animation: spin 1s infinite linear;
}

.loader-text {
    margin-top: 15px;
    color: #8c8375;
    font-size: 0.9rem;
    letter-spacing: 1px;
}

@keyframes spin {
    0% { transform: rotate(0deg); }
    100% { transform: rotate(360deg); }
}

/* Maximized viewport wrapper with tiny vertical padding */
#viewport-wrapper {
    position: relative;
    width: 100vw;
    height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
    padding: 5px 20px;
    touch-action: none;
}

/*
#flipbook-wrapper {
    position: relative;
    display: block;
    margin: 0 auto;
    visibility: hidden; 
}

#flipbook-wrapper {
    position: relative;
    display: block;
    margin: 0 auto;
    visibility: hidden;
    
    transform-origin: center center; 
    will-change: transform;
    transition: transform 0.1s ease-out;
}
*/
#flipbook-wrapper {
    position: relative;
    display: block;
    margin: 0 auto;
    visibility: hidden;
    transform-origin: center center;
    will-change: transform;
    user-select: none;          /* Block accidental system highlights */
    -webkit-user-select: none;
}


#flipbook {
    display: block;
    margin: 0 auto;
}

#flipbook .page-node {
    background-color: #faf8f5;
    overflow: hidden;
    width: 100%;
    height: 100%;
}

#flipbook img {
    width: 100%;
    height: 100%;
    object-fit: contain;
    display: block;
    pointer-events: none;       
    -webkit-user-drag: none;    /* Strict browser drag execution lockdown */
}

/* Soft center fold depth shadows */
#flipbook .odd .page-node {
    background-image: linear-gradient(to left, rgba(0,0,0,0.10) 0%, rgba(0,0,0,0.02) 4%, rgba(0,0,0,0) 10%);
}

#flipbook .even .page-node {
    background-image: linear-gradient(to right, rgba(0,0,0,0.10) 0%, rgba(0,0,0,0.02) 4%, rgba(0,0,0,0) 10%);
}

/* Soft Minimalist Navigation Arrows */
.nav-btn {
    position: absolute;
    top: 50%;
    transform: translateY(-50%);
    background: rgba(250, 248, 245, 0.4); 
    border: 1px solid rgba(140, 131, 117, 0.15);
    color: #7a7164;
    font-size: 1.6rem;
    width: 54px;
    height: 54px;
    border-radius: 50%;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    z-index: 100;
    transition: all 0.3s ease;
    backdrop-filter: blur(4px);
    -webkit-backdrop-filter: blur(4px);
}

.nav-btn:hover {
    background: rgba(250, 248, 245, 0.8);
    color: #4a443c;
    border-color: rgba(140, 131, 117, 0.3);
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.05);
}

#prev-btn { left: 24px; }
#next-btn { right: 24px; }

@media (max-width: 600px) {
    .nav-btn {
        width: 40px;
        height: 40px;
        font-size: 1.2rem;
    }
    #prev-btn { left: 8px; }
    #next-btn { right: 8px; }
}

/* download button */
#floating-download-btn {
    position: fixed;
    bottom: 24px;
    right: 24px;
    z-index: 1000;
    width: 56px;
    height: 56px;
    background-color: #faf8f5; /* Matches your paper color */
    color: #7a7164;            /* Matches your arrow button color */
    border: 1px solid rgba(140, 131, 117, 0.15);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    opacity: 0.5;              /* Semi-transparent by default */
    transition: all 0.3s ease;
    text-decoration: none;
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.05);
    backdrop-filter: blur(4px);
    -webkit-backdrop-filter: blur(4px);
}

#floating-download-btn:hover {
    opacity: 1;                /* Fully visible on hover */
    background-color: #faf8f5;
    color: #4a443c;
    border-color: rgba(140, 131, 117, 0.3);
    box-shadow: 0 6px 16px rgba(0, 0, 0, 0.1);
    transform: translateY(-2px);
}

#floating-download-btn svg {
    width: 24px;
    height: 24px;
}

/* Shift position slightly on small mobile screens to prevent overlapping arrow buttons */
@media (max-width: 600px) {
    #floating-download-btn {
        bottom: 16px;
        right: 16px;
        width: 48px;
        height: 48px;
    }
    #floating-download-btn svg {
        width: 20px;
        height: 20px;
    }
}

#floating-reset-zoom-btn {
    position: fixed;
    top: 24px;
    right: 96px; 
    z-index: 1000;
    padding: 10px 16px;
    background-color: rgba(250, 248, 245, 0.6); 
    color: #7a7164;            
    border: 1px solid rgba(140, 131, 117, 0.15);
    border-radius: 30px;       
    display: flex;
    align-items: center;
    gap: 8px;
    cursor: pointer;
    font-family: system-ui, sans-serif;
    font-size: 0.85rem;
    font-weight: 500;
    opacity: 0;                
    visibility: hidden;
    pointer-events: none;
    transition: opacity 0.3s ease, transform 0.3s ease, background-color 0.3s ease;
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.05);
    backdrop-filter: blur(4px);
    -webkit-backdrop-filter: blur(4px);
}

#floating-reset-zoom-btn:hover {
    opacity: 1 !important;     
    background-color: rgba(250, 248, 245, 0.9);
    color: #4a443c;
    border-color: rgba(140, 131, 117, 0.3);
    box-shadow: 0 6px 16px rgba(0, 0, 0, 0.1);
    transform: translateY(-1px);
}

#floating-reset-zoom-btn svg {
    width: 18px;
    height: 18px;
}

/* Rigid position overlay locks for mobile viewport boundaries */
@media (max-width: 600px) {
    #floating-reset-zoom-btn {
        position: fixed !important; /* Force layout isolation */
        top: 16px !important;
        right: 16px !important;    /* Shift away from nav conflict points */
        left: auto !important;
        padding: 8px 12px;
        font-size: 0.8rem;
    }
    #floating-reset-zoom-btn span {
        display: none; 
    }
}