* { box-sizing: border-box; }
body {
    margin: 0;
    display: flex;
    min-height: 100vh;
    perspective: 1000px;
    font: 1em/1.4 "Poppins", sans-serif;
    overflow: hidden;
    color: hsl(180 68% 5%);
    background-image: radial-gradient(circle farthest-corner at 50% 50%, hsl(187 20% 88%) 30%, hsl(149 20% 94%) 100%);
}

/* Loading Screen Styles */
#loading-screen {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    background: rgba(255, 255, 255, 0.9);
    z-index: 1000;
}

.loader {
    border: 8px solid #f3f3f3;
    border-top: 8px solid #3498db;
    border-radius: 50%;
    width: 60px;
    height: 60px;
    animation: spin 1s linear infinite;
}

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

#loading-screen p {
    margin-top: 20px;
    font-size: 1.2em;
    color: #333;
}

/* Book Styles */
.book {
    position: relative;
    display: flex;
    margin: auto;
    width: 30vw;  /* Adjusted for portrait orientation */
    height: 90vh; /* Adjusted for portrait orientation */
    pointer-events: none;
    transform-style: preserve-3d;
    transition: translate 1s;
    translate: calc(min(var(--c), 1) * 50%) 0%;
    rotate: 0deg;
}

.page {
    --thickness: 4;
    flex: none;
    display: flex;
    width: 100%;
    height: 100%;
    pointer-events: all;
    user-select: none;
    transform-style: preserve-3d;
    transform-origin: left center;
    transition: transform 1s, rotate 1s ease-in calc((min(var(--i), var(--c)) - max(var(--i), var(--c))) * 50ms);
    translate: calc(var(--i) * -100%) 0px 0px;
    transform: translateZ(calc((var(--c) - var(--i) - 0.5) * calc(var(--thickness) * .23vh)));
    rotate: 0 1 0 calc(clamp(0, var(--c) - var(--i), 1) * -180deg);
}

.front, .back {
    position: relative;
    flex: none;
    width: 100%;
    height: 100%;
    backface-visibility: hidden;
    overflow: hidden;
    background-color: #fff;
    translate: 0px;
}

.back {
    translate: -100% 0;
    rotate: 0 1 0 180deg;
}

.book {
    counter-reset: page -1;
}

.page {
    box-shadow: 0em .5em 1em -.2em #00000020;
}

.cover::after {
    content: "";
}

.front::after {
    right: 1em;
}

.front {
    background: linear-gradient(to left, #f7f7f7 80%, #eee 100%);
    border-radius: .1em .5em .5em .1em;
}

.back::after {
    left: 1em;
}

.back {
    background-image: linear-gradient(to right, #f7f7f7 80%, #eee 100%);
    border-radius: .5em .1em .1em .5em;
}

.cover .front {
    background: url('cover.png') 50% / cover no-repeat;
    background-color: #fff;
}

.button-page .front, .button-page .back {
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.5em;
    cursor: pointer;
}

.button-page .back {
    display: none; /* Hide the back of the button page */
}